Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: gwhitf on June 05, 2009, 07:20:34 pm
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Today, I tested three Hasselblad HC lenses for this witchcraft term "diffraction" that I've heard thrown around on this forum. I thought it was hogwash.
It is not. Maybe it's more critical with digital than film. I don't know. I'm not a scientist. But I know sharp from soft.
I tested the 35mm HC, the 50mm HC, and the 80mm HC, on an H2 body with a P45+. I tested it tethered, inside, using strobe to eliminate camera shake. Shutter at 800th. Profoto head adjusted each time, dialed down one stop so the light would not have to move.
The range was, in general f8 to f22, in full stops. The files are too large to post here; no use in posting an artifacted JPG, when we're discussing subtleties like this.
But in general, my advice is to NEVER shoot an HC lens any smaller than f11. Even f16 shows noticeable softness, and 22 is a joke, and let's not even talk about 32 or 45.
So boys, instead of just "stopping down and carrying focus", you'd better be learning to shoot focus brackets, and build the layers. No, not good news at all.
If Mr. Grover reads this, meet me on the corner of Main and Sorrow, at high noon, and I'll turn over the bad news files.
My hunch is that this factor affects every brand, although I'm sure there are some differences between brands. My advice: TEST YOUR OWN GEAR. Do not rely on my information, or any other hearsay. Just take this as a warning. Just because it says Zeiss or Planar or whatever on the front, it only means that some of the fstops are sharp. Test your own stuff so that you know your own gear.
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But in general, my advice is to NEVER shoot an HC lens any smaller than f11. Even f16 shows noticeable softness, and 22 is a joke, and let's not even talk about 32 or 45.
Your standards might be too high here. For example, virtually all of the softness you see at f/16 when using sensors with 6 or 6.8 micron pixels can be recovered by proper sharpening. The reason is that even at f/16 you still have some MTF at the Nyquist limit of the sensor. So in this case all of the information that the sensor is capable of capturing is in the image, but you need post-processing to make the most of it.
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I'd like to see and 'equal DoF' comparison between the P45+ and the Canon G10. Such a comparison would entail using the G10 at it's sharpest aperture of around F3.5 or F4, and the P45+ at F22 or F25.
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Yes "George", this witch effect called diffraction affects all brands equally.
Under same f-stop/sensor/pixel size or pitch, there is absolutely no difference concerning diffraction, from a lens to another: once you have reached a certain limit-aperture, diffraction is there and affecting equally all lenses. So there are no differences between brands, concerning this optical effect.
I wonder also why this seems to be new, when one of the main reasons for using a view camera IS diffraction: effectively, a view camera is used to be able to set the sharpness plane the best possible way to reduce the stopping-down (Scheimpflug rule), respectively to change the extension direction of the DOF, and THEREFORE to be able to use the lens at its best f-stop: what does it bring to buy expensive glass, when one simply stops down and enters diffraction in the equation? Better in this case to buy a cheap glass, the effect will be the same. Alternatively the view camera allows to tilt/swing the sharpness plane for special sharpness effects, but one often forgets that diffraction is the main reason of using a view camera, together with perspective corrections.
I have said it many times, f16 is for me the limit when stopping down with a 33/39 MPx sensor, without any noticeable alteration of the image.
Best regards,
Thierry
My hunch is that this factor affects every brand, although I'm sure there are some differences between brands. My advice: TEST YOUR OWN GEAR. Do not rely on my information, or any other hearsay. Just take this as a warning. Just because it says Zeiss or Planar or whatever on the front, it only means that some of the fstops are sharp. Test your own stuff so that you know your own gear.
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Naturally you should be careful with stopping down beyond f11/f16. Nothing new you are telling here.
I can tell you that with Schneider Digitars it is even worse. I wonder how that is possible since according Thierry all lenses should be affected equally? I don't think that is entirely the case. These show diffraction starting from f11 and f16 is already total garbage. Much more so than my HC lenses. Even between those there are differences.
Thierry is right this is where movements are for. The DoF is already very thin (we seem to have become much more critical with digital, acceptable sharpness needs to be redefined), even f16 doesn't give you a whole lot so if you need DoF you really need to have movement.
Even with my view camera movements are sometimes not enough. Try a cubus-like item from close-up. You will find you have to compromise somewhere (if you don't want to focus-bracket your way out).
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I can tell you that with Schneider Digitars it is even worse. I wonder how that is possible since according Thierry all lenses should be affected equally? I don't think that is entirely the case. These show diffraction starting from f11 and f16 is already total garbage. Much more so than my HC lenses. Even between those there are differences.
All lenses of equal focal length set to an equal aperture are affected equally by the laws of physics. Are you talking about the same focal lengths? The determining factor is the size of the hole, whose diameter is focal_length/aperture. View cameras generally use lenses of greater focal length and so the hole is larger, i.e. less diffraction. The shape of the aperture blade edge might make a difference though, so one lens might differ a touch from another of identical focal length at the same aperture. There shouldn't be huge differences though.
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So boys [...] No, not good news at all.
So boy: what's the point for you? You never noticed it. Either you never used f stops smaller than f16 or you don't care about sharpness. Keep shooting as usual - that simple.
And take a look at Helicon Focus...
If Mr. Grover reads this...
Your dealer didn't comment anything about diffraction?
The jump start of my dealer was the advice to use mirror lock down from 1/60'' and to avoid apertures smaller than f16 (and a side note on moirée)... and to figure out the rest by myself...
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All lenses of equal focal length set to an equal aperture are affected equally by the laws of physics. Are you talking about the same focal lengths? The determining factor is the size of the hole, whose diameter is focal_length/aperture. View cameras generally use lenses of greater focal length and so the hole is larger, i.e. less diffraction. The shape of the aperture blade edge might make a difference though, so one lens might differ a touch from another of identical focal length at the same aperture. There shouldn't be huge differences though.
Kind of difficult to compare I guess. I have the 120/5.6macro & 90/4.0 of the Schneiders and I mostly use the HC100/2.2. I noticed that the Schneiders I can only use up to f11 max but that is already pushing it. The HC100/2.2 I often use at that aperture and performs much better than either one of the Schneiders at that range of apertures. Anything below f11 the HC lens is no match for the Schneiders with the exception of (software corrected) CA.
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virtually all of the softness you see at f/16 when using sensors with 6 or 6.8 micron pixels can be recovered by proper sharpening.
I agree.
Sometimes it's useful to use f16 because the image gets more even. At f11 and especially at f8 the focal plane is incredibly sharp - looks like there is a thin layer of extra sharpening. But only in the center of the image! In the post you push the corner sharpness much more than the center. With f16 the image is not really less sharp at the edges than at f11 - it's just the center that has less contrast. So with f16 you set a more even sharpness and end up with roughly the same as with f11 (but you have more DOF). Well... at leat that's my experience...
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Kind of difficult to compare I guess. I have the 120/5.6macro & 90/4.0 of the Schneiders and I mostly use the HC100/2.2. I noticed that the Schneiders I can only use up to f11 max but that is already pushing it. The HC100/2.2 I often use at that aperture and performs much better than either one of the Schneiders at that range of apertures. Anything below f11 the HC lens is no match for the Schneiders with the exception of (software corrected) CA.
Ah, I forgot something: not all lenses are diffraction-limited. In other words, some designs show weakness before real diffraction sets in. It may be that Schneider has made some compromise at small apertures in favour of more sharpness at large apertures. This is a bit beyond my knowledge though.
A second point is that, IIRC from my physics classes, diffraction depends on the shape of the edge, and its "texture". It could be that the Hasselblad HC lenses use better materials and design of aperture blades.
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hi Dustback,
I wouldn't know why an aperture of f16 on a Schneider lens (in your case a Digitar) would give more diffraction than any other brand of lens at the same f16. It's simple, the aperture is equal for all lenses, at a certain given f-stop, letting through the same amount of light for a given exposure time, provided that all other parameters are equal. One important parameter, one possibility in your discovery, could be the reproduction scale: one often forgets that the effect of diffraction gets worse with the reproduction scale becoming bigger. In this case, the distance lens to sensor plane increases, respectively the diffraction "circles" created become bigger and more noticeable. In other words, a diffraction effect with a certain f-stop should (is) always be given at a certain reproduction scale, in data sheets, usually at infinity.
When I was speaking about f16 being a limit for 33/39 MPx sensors, I was refering to a reproduction scale of infinity. Taking a scale of e.g. 1:1 (subject = reproduction size), the critical f-stop is MUCH less, respectively 2 f-stops less, and this is in total accordance with the distance lens to sensor (or film), which is then twice the distance as at infinity. Twice the distance means 4 times less light reaching the sensor (film): remember, light decreases by the square of the distance. Which in return brings us to square one: an engraved f-stop of 16 at a reproduction scale of 1:1 is nothing else but a REAL f-stop of 32. And that is certainly "total garbage" as you put it, with a 33/39 MPx sensor.
Now, I am not saying that you were experiencing this at R = 1:1, but it might be the reason.
Best regards,
Thierry
I can tell you that with Schneider Digitars it is even worse. I wonder how that is possible since according Thierry all lenses should be affected equally? I don't think that is entirely the case. These show diffraction starting from f11 and f16 is already total garbage. Much more so than my HC lenses. Even between those there are differences.
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Carsten,
when we are speaking about the focal length, then we automatically introduce the other important factor in diffraction effects: the reproduction scale/distance lens-sensor.
Best regards,
Thierry
All lenses of equal focal length set to an equal aperture are affected equally by the laws of physics. Are you talking about the same focal lengths? The determining factor is the size of the hole, whose diameter is focal_length/aperture. View cameras generally use lenses of greater focal length and so the hole is larger, i.e. less diffraction. The shape of the aperture blade edge might make a difference though, so one lens might differ a touch from another of identical focal length at the same aperture. There shouldn't be huge differences though.
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What's true is, I have no idea about other brands of lenses and whether they'd produce the same surprising results either. My message is for everyone to simply take the time and test their own gear, so they'd KNOW, and not assume. To me, there's no upside to trying to apply USM to an image to try to bring it back sharp again. Just like when you'd throw a loupe on a piece of E6 in the old days, "it's either tack sharp or it's not", and if it's not, it bugs me.
I would hope that the Contax line or Mamiya line would not show this diffraction past f11. What I was surprised at was the AMOUNT of deteriation past f16. I did the test with Sharpening disabled completely in 3.79, and no other USM was applied in Photoshop later. I wanted to see the real data.
Maybe I just feel like an idiot for not doing this detailed test sooner. I plead guilty to seeing the Hasselblad logo and trusting that it'll be sharp. Color me embarrassed. I'd love to do the test with the Canon line of lenses, and on the other end, with lenses on a technical camera like an Alpa or ArTec. Just to see for myself.
There are times, shooting people, or working fast, where it's simply not possible to shoot "focus brackets" in layers, and then also to devote the time for post, to build every image. The whole test was a real wake-up call for me. That's all I'm saying.
Test away.
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That is absolutely true, though I am tempted to think that most manujfacturers are using the same shape of blades and that even a little difference in this shape should make a difference of 1 stop or more when diffraction is visible.
However, I have no clue here as well, and speaking out of my own experience.
Thierry
A second point is that, IIRC from my physics classes, diffraction depends on the shape of the edge, and its "texture". It could be that the Hasselblad HC lenses use better materials and design of aperture blades.
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The whole test was a real wake-up call for me.
So that's a good thing - just be happy!
I did the test with Sharpening disabled completely in 3.79, and no other USM was applied in Photoshop later. I wanted to see the real data.
Did you set the sharpening slider to zero or did you disable sharpening in the preferences/menu?
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I agree here. I never ever go above f16 on any of my Hasselblad H prime lenses on my 45+ back or even a lesser resolution back for that matter. Eleanor
I have said it many times, f16 is for me the limit when stopping down with a 33/39 MPx sensor, without any noticeable alteration of the image.
Best regards,
Thierry
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hi Dustback,
I wouldn't know why an aperture of f16 on a Schneider lens (in your case a Digitar) would give more diffraction than any other brand of lens at the same f16. It's simple, the aperture is equal for all lenses, at a certain given f-stop, letting through the same amount of light for a given exposure time, provided that all other parameters are equal. One important parameter, one possibility in your discovery, could be the reproduction scale: one often forgets that the effect of diffraction gets worse with the reproduction scale becoming bigger. In this case, the distance lens to sensor plane increases, respectively the diffraction "circles" created become bigger and more noticeable. In other words, a diffraction effect with a certain f-stop should (is) always be given at a certain reproduction scale, in data sheets, usually at infinity.
When I was speaking about f16 being a limit for 33/39 MPx sensors, I was refering to a reproduction scale of infinity. Taking a scale of e.g. 1:1 (subject = reproduction size), the critical f-stop is MUCH less, respectively 2 f-stops less, and this is in total accordance with the distance lens to sensor (or film), which is then twice the distance as at infinity. Twice the distance means 4 times less light reaching the sensor (film): remember, light decreases by the square of the distance. Which in return brings us to square one: an engraved f-stop of 16 at a reproduction scale of 1:1 is nothing else but a REAL f-stop of 32. And that is certainly "total garbage" as you put it, with a 33/39 MPx sensor.
Now, I am not saying that you were experiencing this at R = 1:1, but it might be the reason.
Best regards,
Thierry
You might be right here. Most of the time I use the Digitars closer than the HC lenses, a lot closer actually. The reason I grab the X-act2 is because I am so close my DoF is not sufficient enough anymore and I need movements. Figures how much closer I am
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All lenses of equal focal length set to an equal aperture are affected equally by the laws of physics. Are you talking about the same focal lengths? The determining factor is the size of the hole, whose diameter is focal_length/aperture. View cameras generally use lenses of greater focal length and so the hole is larger, i.e. less diffraction.
I can tell you that with Schneider Digitars it is even worse. I wonder how that is possible since according Thierry all lenses should be affected equally? I don't think that is entirely the case. These show diffraction starting from f11 and f16 is already total garbage. Much more so than my HC lenses. Even between those there are differences.
Even with my view camera movements are sometimes not enough. Try a cubus-like item from close-up. You will find you have to compromise somewhere (if you don't want to focus-bracket your way out).
Sharpness is relative, and when using short Schneider Apo-Digitars with 5 micron pixels at f4 to f8, you are looking sharpness beyond what is possible with (most) other lenses: cheap lenses seem to have more DOF because, by apo-digitar standards, they are never sharp.
All the relevant formulae are in Harold Merklinger's "Focussing the View Camera".
DOF merge is often the only way to get good depth of field: digital provides the solutions for the problems it creates (or makes apparent - diffraction was not a problem when the resolution of film was the limiting factor).
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I wouldn't know why an aperture of f16 on a Schneider lens (in your case a Digitar) would give more diffraction than any other brand of lens at the same f16. It's simple, the aperture is equal for all lenses, at a certain given f-stop, letting through the same amount of light for a given exposure time, provided that all other parameters are equal.
I think you actually answered why with the last 7 words above, "provided that all other parameters are equal;" in most cases, all of the other parameters are not generally going to be equal...
In actuality, the best lenses will show diffraction more readily than lesser lenses; the sharper the lens is, the easier it is to see when and where diffraction anomalies kick in. (As to why it's more of a problem with digital than film, I suspect it's because we can easily view our direct digital captures at 100%, where with film one would have to have a perfect scan or perfect analog enlargement first to view it, and perfect scans are difficult enough where perfect analog enlargements are rare to non-existent.) So in this case, I would submit the Schneider Digitars (or Rodenstock HR digitals) being among the best glass available for digital sensors, will show diffraction issues more readily than even the best MF lenses, regardless of brand.
The other issue is MF lenses have to deal with a fixed point flange-focal for the camera's mounting system, where the Schneider or Rodenstock are not thusly design-constrained. The single exception may be lenses in the 80mm focal length for MF cameras, as these lenses usually have flange focals very close to the lens focal to begin with, so the best are probably nearly as good as the Schneider/Rodenstock equivalent. In reality, even 50mm through 120mm MF lenses may be close enough to the system's flange focal that the design constraints are not overly detrimental to the final image quality.
Cheers,
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I just feel like I've learned a good lesson by doing these tests. I just never in a million years thought it would affect the golden brand,
(Actually, I have a Sigma 70mm 2.8 for the Canon, and it's the sharpest lens in my Canon case, so go figure).
Multiple tests so far, and the sweet spot with the 35, 50, and 80 HC are between f5.6 and f11. If resolution and absolute sharpness is the goal. At least these are my findings. Scary, scary territory past f16; only venture into those woods with extreme caution.
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I just feel like I've learned a good lesson by doing these tests. I just never in a million years thought it would affect the golden brand,
(Actually, I have a Sigma 70mm 2.8 for the Canon, and it's the sharpest lens in my Canon case, so go figure).
Multiple tests so far, and the sweet spot with the 35, 50, and 80 HC are between f5.6 and f11. If resolution and absolute sharpness is the goal. At least these are my findings. Scary, scary territory past f16; only venture into those woods with extreme caution.
A friend of mine recommended the Sigma. At first I spewed coffee and choked, thinking about actually owning a Sigma lens, but thought I'd give it a try and though I'm not somebody that pixel compares this stuff, the Sigma is the sharpest "smaller than larger sensor format" lens I own. On the d3 and D700 it's brilliant and well built.
Kind of scary actually.
JR
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I just feel like I've learned a good lesson by doing these tests. I just never in a million years thought it would affect the golden brand,
(Actually, I have a Sigma 70mm 2.8 for the Canon, and it's the sharpest lens in my Canon case, so go figure).
Multiple tests so far, and the sweet spot with the 35, 50, and 80 HC are between f5.6 and f11. If resolution and absolute sharpness is the goal. At least these are my findings. Scary, scary territory past f16; only venture into those woods with extreme caution.
I have not personally verified it through my own tests, but no less an authority than Joe Holmes personally assured me that f/16 is the limit and it provides excellent sharpness IF you use what he believes are the very best capture sharpening programs. He likes Raw Developer's R-L Deconvolution, Focus Magic and Smart Sharpen. Since he forgets more about this stuff in a minute than I will ever know, I follow his advice. Oh, and I am happy with the results I get with each of these programs. The one hangup with Focus Magic is that it is not a Universal Binary, so I go to CS3 if I want to use it.
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with "other parameters" was meant the reproduction scale, resp.the distance lens-sensor/film, or in other words, the shoooting distance, resp. the focal length.
That are all the parameters affecting the diffraction, with the exception of the blades' shape, which IMO has no real visible difference and can be considered as minime.
Obviously, if you are using a bottle glass in front of your camera, that doesn't matter anymore, it will be bad anyway and your IQ is already affected by the built-quality: I wouldn't say that the Digitars are badly designed lenses.
Thierry
I think you actually answered why with the last 7 words above, "provided that all other parameters are equal;" in most cases, all of the other parameters are not generally going to be equal...
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I wouldn't say that the Digitars are badly designed lenses.
I didn't say that either, in fact I said the opposite. What I did say was that diffraction is easier to spot sooner in lenses that are sharper.
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All lenses of equal focal length set to an equal aperture are affected equally by the laws of physics. Are you talking about the same focal lengths? The determining factor is the size of the hole, whose diameter is focal_length/aperture. View cameras generally use lenses of greater focal length and so the hole is larger, i.e. less diffraction.
I think you might be confusing DoF requirements with diffraction effects here. When using different format cameras, in order to get equal DoF on equal FoV images on equal size prints, the physical aperture sizes should be equal on the respective lenses used. This entails using different focal length lenses to achieve the same FoV, and different f stops on those lenses of different focal lengths to achieve the same DoF.
For example, an 8"x10" field camera used with 400mm lens will produce the same FoV as a 35mm format used with 50mm lens (ignoring differences in aspect ratio). In order to get the same DoF using the 8x10 format without using tilt and swing, you would need to stop down by a factor of 8. If you use F8 with the 35mm format, you would need to use F64 with the 8x10 format (50/8=400/64).
When using different FL lenses on the same format, the longer focal length, at say F16, will have a larger physical diameter and therefore should produce less diffraction effects as the light passes through the opening. However, as Thierry mentioned, the entire image is enlarged at the sensor when using the longer focal length, including the initially smaller effects of diffraction.
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I did refer to Dustback's remark about his Digitars.
However, I fully disagree with your statement about "affecting" sooner with better lenses: what is already spoiled by the glass in terms of sharpness can't be spoiled more by diffraction. In that perspective, a bad lens remains bad, a good lens gets its produced images affected, the more with f-stops becoming higher.
It has nothing to do with "earlier" or "sooner": that is misleading and leads to think that the effect is bigger on good lenses.
Thierry
I didn't say that either, in fact I said the opposite. What I did say was that diffraction is easier to spot sooner in lenses that are sharper.
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I did refer to Dustback's remark about his Digitars.
However, I fully disagree with your statement about "affecting" sooner with better lenses: what is already spoiled by the glass in terms of sharpness can't be spoiled more by diffraction. In that perspective, a bad lens remains bad, a good lens gets its produced images affected, the more with f-stops becoming higher.
It has nothing to do with "earlier" or "sooner": that is misleading and leads to think that the effect is bigger on good lenses.
Thierry
Must be a language barrier... Please re-read what I wrote. I said, "diffraction is easier to spot sooner in lenses that are sharper." Note that I did NOT say it is "affecting" sooner in sharper lenses, only that it is easier to *spot* sooner
PS: Just curious Thierry, what are you doing for work now?
Cheers,
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Must be!
However, my comprehension of your sentence
... In actuality, the best lenses will show diffraction more readily than lesser lenses" ...
is that better lenses show it more, faster, whereby I have to admit that I don't understand the word "readily": the Italian translation gives "faster", the German "already", and the Spanish "easier".
Thierry
PS: I have not yet decided about my professional future, simply enjoying my time and the present.
Must be a language barrier... Please re-read what I wrote. I said, "diffraction is easier to spot sooner in lenses that are sharper." Note that I did NOT say it is "affecting" sooner in sharper lenses, only that it is easier to *spot* sooner
PS: Just curious Thierry, what are you doing for work now?
Cheers,
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I have to admit that I don't understand the word "readily": the Italian translation gives "faster", the German "already", and the Spanish "easier".
In English, the word "readily" is an adverb that means, to do without difficulty or easily. Being an adverb it is also implied as an action, hence the to do...
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Alright, in this case we do agree.
I simply wish to emphasize here the importance of the lens, not in relation with diffraction: it is the most critical element in the quality chain, hence if you wish best image quality use the best lenses.
Thierry
In English, the word "readily" is an adverb that means, to do without difficulty or easily. Being an adverb it is also implied as an action, hence the to do...
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Definitely there are some differences from lens to lens even considering the same mount and focal length etc. at least from my testing. While these differences could be chalked up to aperture design and placement in the lens, my guess is the magnification factor is more important. I think this was touched on but image circle or magnification factor are important to consider with regard to diffraction effects. I would expect the lenses with larger image circles to be limited at higher numerical f-stop values all else considered. I guess I could test this out with my rollei 150mm apo macro which purportely has a huge image circle against my 150mm tele-xenar both the same focal length and made by Schneider.
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I think you might be confusing DoF requirements with diffraction effects here.
No, I meant it as I wrote it. DoF is clearly a separate issue. I wasn't aware that the same size hole in lenses for different formats would result in identical depth of field. I will have to work through the math to verify that for myself.
When using different FL lenses on the same format, the longer focal length, at say F16, will have a larger physical diameter and therefore should produce less diffraction effects as the light passes through the opening. However, as Thierry mentioned, the entire image is enlarged at the sensor when using the longer focal length, including the initially smaller effects of diffraction.
Right, I was only speaking to the first sentence here. I haven't yet worked through the effect of using similar focal lengths on different systems. I was writing about using lenses designed for different uses on the same sensor. In this scenario, it doesn't matter what the size of the image circle is, or any other parameters. If the focal length is equal, the diffraction is equal at equal apertures for different lenses. That doesn't mean that the image is equally blurry though, just that the part attributable to diffraction is equal.
Diffraction is always present. It is not something that "kicks in" at larger apertures. Diffraction happens when light passes an edge. What happens at smaller aperture openings is that this part of the light passing through the lens starts to dominate the overall photo.
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In actuality, the best lenses will show diffraction more readily than lesser lenses; the sharper the lens is, the easier it is to see when and where diffraction anomalies kick in. (As to why it's more of a problem with digital than film, I suspect it's because we can easily view our direct digital captures at 100%, where with film one would have to have a perfect scan or perfect analog enlargement first to view it, and perfect scans are difficult enough where perfect analog enlargements are rare to non-existent.) So in this case, I would submit the Schneider Digitars (or Rodenstock HR digitals) being among the best glass available for digital sensors, will show diffraction issues more readily than even the best MF lenses, regardless of brand.
I have to agree with Jack Flesher here.
Diffraction is a constant that varies only with aperture diameter. It exists to some degree at all apertures, in proportion to physical aperture diameter. It exists at F2.8, but is so small that it's irrelevant compared with diffraction effects at F16 which begin to rear their head.
Diffraction is something we can do little about. Its effects are proportional to F stop.
If a lens is sharpest at F5.6, it's because all the other lens distortions types have been reduced below the diffraction limit that applies to the aperture. (Is that clear, or is it gobbledegook?)
If a lens is sharpest at F16, (and some 35mm zooms are), it's because all the aberrations other than diffration, coma and astigmatism etc, are so lousy, that the lens is lousy.
Diffraction effects are completely embedded in the laws of Physics. But at F2.8 they're so small as to be insignificant.
At F16, resolution is limited by diffraction. One could say, all lenses are equal at F16, no matter how hard the lens designers work.
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After testing, I could make a case to just have TWO fstops on a "serious" lens -- one of the fstops would be wide open, for focusing and composing, and then once you nailed that, you'd push a button, and it would stop the lens down to it's sharpest Fstop. That might be f5.6 and two thirds, or F8 and a 5/16's, or whatever each particular lens design peaked out at.
I'm putting the final touches on my own new Hasselblad firmware update today -- when you're shooting in the range of f4 - f11, the areas around the frame, in the viewfinder, flash green. But when you stop down to f16, the area in the viewfinder outside the frame begins to turn bright red, to caution you. And if you're man enough to stop down past f16, then all kinds of warning lights flash off and on in the viewfinder, to get your attention. At f32, a Smoke Machine is activated, inside the viewfinder, and the entire viewfinder fills with smoke, to purposely block your vision of the frame. With the 120 HC lens, when you go to F45, the H2 body simply detonates in your hands, to keep you from blowing the job.
I'm also filing suit against my college professor that taught me, "just shoot at f22 if you want to carry focus throughout the entire frame, for maximum depth". After that, I'm heading to Retouching University, to learn how to shoot Foreground Focus Layers, and Background Focus Layers, and then stitch them together.
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After testing, I could make a case to just have TWO fstops on a "serious" lens -- one of the fstops would be wide open, for focusing and composing, and then once you nailed that, you'd push a button, and it would stop the lens down to it's sharpest Fstop.
Now you need to read up on another common lens design anomaly -- "focus shift."
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Ah... such a delight for focus bracketing
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Here's a link to an aperture study I had done of one of my large format lenses on film:
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Now you need to read up on another common lens design anomaly -- "focus shift."
Fortunately corrected on all H cameras.
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After testing, I could make a case to just have TWO fstops on a "serious" lens -- one of the fstops would be wide open, for focusing and composing, and then once you nailed that, you'd push a button, and it would stop the lens down to it's sharpest Fstop. That might be f5.6 and two thirds, or F8 and a 5/16's, or whatever each particular lens design peaked out at.
I'm putting the final touches on my own new Hasselblad firmware update today -- when you're shooting in the range of f4 - f11, the areas around the frame, in the viewfinder, flash green. But when you stop down to f16, the area in the viewfinder outside the frame begins to turn bright red, to caution you. And if you're man enough to stop down past f16, then all kinds of warning lights flash off and on in the viewfinder, to get your attention. At f32, a Smoke Machine is activated, inside the viewfinder, and the entire viewfinder fills with smoke, to purposely block your vision of the frame. With the 120 HC lens, when you go to F45, the H2 body simply detonates in your hands, to keep you from blowing the job.
I'm also filing suit against my college professor that taught me, "just shoot at f22 if you want to carry focus throughout the entire frame, for maximum depth". After that, I'm heading to Retouching University, to learn how to shoot Foreground Focus Layers, and Background Focus Layers, and then stitch them together.
Hi Mr T,
Further to your original post then I guess you have highlighted something that you have heard is not unknown and wasn't news to me. Sorry to disappoint. ;-)
But anyway, the lesson is I guess to find the limits of your own gear so not caught with your pants down.
I have forwarded your firmware ideas to R&D for comment.
Best,
David
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Hi Mr T,
Further to your original post then I guess you have highlighted something that you have heard is not unknown and wasn't news to me. Sorry to disappoint. ;-)
But anyway, the lesson is I guess to find the limits of your own gear so not caught with your pants down.
I have forwarded your firmware ideas to R&D for comment.
Best,
David
David,
In all seriousness, let's say you wanted to go Gursky and shoot a scene in times square where you pulled tight detailed 50mpx focus from front subject to background on a very large print, (think moving people that are sharp.
How would you do this with a 80mm or even a 50mm lens in digital?
B
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David,
In all seriousness, let's say you wanted to go Gursky and shoot a scene in times square where you pulled tight detailed 50mpx focus from front subject to background on a very large print, (think moving people that are sharp.
How would you do this with a 80mm or even a 50mm lens in digital?
B
Without setting up the shot, it would be hard to guess what the limits are on DOF.
I actually don't think it would be too much of a struggle with the 50mm.
Depending on the shot you could use the HTS with a bit of tilt to improve the DOF, IF you weren't too worried about tops of Time Square sky scrapers being in Focus.
Otherwise, you can't...
D
EDIT... Just to show it is not all bad, this shot with the 28mm is at f16. Everything is sharp from front to back. (Front being the chest of draws in the FG, back being the small Lion statue in the back left corner)
(http://i85.photobucket.com/albums/k70/dgrover/28only.jpg)
(http://i85.photobucket.com/albums/k70/dgrover/bottleft.jpg)
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After testing, I could make a case to just have TWO fstops on a "serious" lens -- one of the fstops would be wide open, for focusing and composing,
We like to have the option to make our own decisions, and be able to expand DOF to the point where we consider diffraction becomes the limiting factor, and (sometimes) avoid bracketing for DOF merge. (... and sometimes we might not have a view camera, or we are unable to get ideal DOF even with movements.)
I'm also filing suit against my college professor that taught me, "just shoot at f22 if you want to carry focus throughout the entire frame, for maximum depth". After that, I'm heading to Retouching University, to learn how to shoot Foreground Focus Layers, and Background Focus Layers, and then stitch them together.
Not many
If you want foreground and background (and main subject) in focus read Merklinger's "Focusing The View Camera" and put a view camera on the front of your Hasselblad DCU... or you might try to make do with one of those HTS T/S adaptors.
Before posting this, I see that David has made comments which, I think, agree with what I have said above, and illustrated a compromise between DOF and diffraction.
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Depending on the shot you could use the HTS with a bit of tilt to improve the DOF, IF you weren't too worried about tops of Time Square sky scrapers being in Focus.
Otherwise, you can't...
Correct me if I am wrong, but it would seem to me that if you can orient the plane of sharpest focus so that it covers all moving elements, cars, people, etc., then you could do a second shot where you got the tops of the skyscrapers in focus, and use Helicon to combine them. Wouldn't this work? I don't see any particular reason to have to work front-to-back with Helicon. Bottom-to-top should work too, I would hope.
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I have forwarded your firmware ideas to R&D for comment.
Best,
David
David,
Kudos and Respect to you for responding on this thread.
I have certainly learned some things about the limitations of my HC lenses, yet I continue to love them more every day, as I get to know them. (I have the same relationships like this with women -- at first I love ever trait, then I discover their shortcomings, while I, of course, remain perfect).
No disrespect meant toward Hasselblad whatsoever, but I must admit, my bubble was burst a small bit when I saw the small-aperture results. But mostly I felt like I had egg on my face for not doing this test about twenty-five years ago. I feel like a chump. (But maybe it was not so much an issue with EPR or any other 120 film).
I will zip the files and send them to you. There are five tests.
I've owned a million Hasselblads in my life, both 500 and 200, (and shot the 680 with Fuji lenses for twenty years too), so my respect for Hasselblad and Fuji is VERY high, (and continues to be).
I want to ask one final question here -- What about The F64 Group? Seriously. They prided themselves on tiny apertures, and unlimited depth of field, (pre-Photoshop). Were they the most misguided group ever, or was it truly a non-issue with film?
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I want to ask one final question here -- What about The F64 Group? Seriously. They prided themselves on tiny apertures, and unlimited depth of field, (pre-Photoshop). Were they the most misguided group ever, or was it truly a non-issue with film?
Diffraction limitation:
- kicks in at higher number f-stops wise with larger formats
- kicks in at higher number f-stops the higher the capture resolution
- is noticeable only if the print is large enough to show it
- is important only if the other elements of quality would have allowed a sharper image*
Examples at the extremes of both ends
- Large prints from a G10 may show diffraction at extremely low f-stop numbers.
- A 3x4" reproduction in a text book from a 16x20 Polaroid camera may not show diffraction at ANY f-stop
The idea of judging quality based on a view which shows the maximum theoretical quality (100% pixel-to-pixel view) is very very recent in the life of photography.
I think the f/64 folks would have been the first to tell you that allowing a *slight* amount of sharpness degradation (visible only in large prints) is sometimes the price you pay to have all parts of the image equally sharp (if that is your artistic intention) since I remember more than one image from my studies where members of that group stopped down past the theoretical diffraction limit for their format.
*e.g. if you're hand holding a 1" exposure than diffraction is not going to be a meaningful limiting factor at any f-stop
Doug Peterson (e-mail Me) (http://mailto:doug@captureintegration.com)
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I think the f/64 folks would have been the first to tell you that allowing a *slight* amount of sharpness degradation (visible only in large prints) is sometimes the price you pay to have all parts of the image equally sharp ...
My tests would indicate that instead of "all parts of the image equally sharp", that the more accurate term would be "all parts of the image would be equally OUT OF FOCUS".
That is the key thing here. You stop down, thinking you're going to carry focus deeper into the frame, when in truth, it's like you're laying a Gaussian Blur layer over the entire photograph. Even the subject area that you wanted tack sharp.
(Edit: Actually, after thinking about this topic, I could almost make the case for shooting a 1ds3 for landscapes, instead of MF, where you wanted to carry focus deeper into the frame, using one frame, and not doing focus brackets. Due to the smaller sensor, and the more inherent depth of focus in the smaller sensor. But that would mean another test, and I don't have it in me right now).
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I want to ask one final question here -- What about The F64 Group? Seriously. They prided themselves on tiny apertures, and unlimited depth of field, (pre-Photoshop). Were they the most misguided group ever, or was it truly a non-issue with film?
They shot with 8x10 view cameras. And it did not supply "unlimited depth of field" for them, just eliminated many aberrations and provided a "comfortable" DoF. The lenses of that period were nowhere near as good as what we have today and needed to be stopped down to remove heavy aberrations. More to the point, f64 on an 8"x10" (200mm x 250mm) piece of film where a 300mm lens is your "normal" is very different than f64 on a 37mm x 49mm sensor where your normal lens is 70mm or so. 8x10 with a 300 lens will show more serious diffraction at around f90 or 128.
Finally, film has two traits a digital sensor does not: One is it has physical depth to emulsion, so captures an image in those 3 dimensions, albeit a dimension that is very shallow; two is halation, where the silver-halide crystals reflect light into neighboring crystals, slightly "fogging" them, which in turn creates edge effects similar to those from -- drum roll -- diffraction. Taken a step further, the fogging causes loss of edge contrast and can cover up some of the diffraction effects -- just like using a "poor" lens can -- so you end up getting a better net image using smaller-than-ideal apertures...
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Fortunately corrected on all H cameras.
Nice! Can you post an example to show us how well it works --- with say the 100 focused on something relatively close, like at about 1 to 1-1/2 meters away, wide open and f5.6 or 8?
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(Edit: Actually, after thinking about this topic, I could almost make the case for shooting a 1ds3 for landscapes, instead of MF, where you wanted to carry focus deeper into the frame, using one frame, and not doing focus brackets. Due to the smaller sensor, and the more inherent depth of focus in the smaller sensor. But that would mean another test, and I don't have it in me right now).
I'd assume the AA filter degrades sharpness in fine details (esp. in low contrast details) more than the diffraction that is visible at f16 compared to f11 on your P45+. But I never tested that (and never will).
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I'd assume the AA filter degrades sharpness in fine details (esp. in low contrast details) more than the diffraction that is visible at f16 compared to f11 on your P45+. But I never tested that (and never will).
It is a known fact that the AA filter does degrade overall image sharpness out of camera. Proper sharpening techniques in post-processing do help correct for that however and should get your image back on track to greatness. The P45+ back does not have an AA filter nor do the Hassy's unlike the Canon's, Nikons and various 35mm DSLRs. Any camera that doesnt have the AA filter over the sensor will show a significant sharpness boost right out of camera. The only con to that is that the AA filter isn't there to handle moire correction. This can be done in post however. The H3D Hassy bodies, their closed system works seamlessly from lens to body to back to post production (via Phocus). They know their hardware and software inside and out and can take into consideration a lot of the little nuances that they couldn't do before with other vendor's backs.
For example, any protective IR filter/glass protecting the H3D backs is taken into account along with APO correction and the like. Numbers are crunched milliseconds before time of capture to account for these nuances to provide you with the best image possible out of camera. In Phocus, lens distortion correction is all done and just apply a sharpening of like 200-300 and then you are pretty much all set with a nice image. Tweak as necessary and proper image capture techniques also help considerably.
Get your hands on the Multi-Shot Hasselblad back and watch that out of camera image detail and sharpness just sing!
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To answer your question is very easy:
no, the "f64" group was not wrong all their years: the f64 group was mainly shooting outdoor landscapes, as such shooting at infinity.
Diffraction is minimum at the infinity scale: when the reproduction size increases, the effect of diffraction becomes more important (see my other post explaining it in details). In additon, this group was shooting on large format, 8x10" or up if I am not mistaken: the diffraction limit, respectively the critical aperture at 4x5" at infinity is theoretically f45, resp. 2 stops more for 8x10" = f90.
Therefore, their claim that f64 was an optimal aperture for them was absolutely right.
Best regards,
Thierry
I want to ask one final question here -- What about The F64 Group? Seriously. They prided themselves on tiny apertures, and unlimited depth of field, (pre-Photoshop). Were they the most misguided group ever, or was it truly a non-issue with film?
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sorry but what's the big deal with all this diffraction? You stop down till necessary for the depth of field that you need for the picture, at a certain print size.
with the resolutions available today chances are you won't even notice these degradation issues till you print huge.
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Correct me if I am wrong, but it would seem to me that if you can orient the plane of sharpest focus so that it covers all moving elements, cars, people, etc., then you could do a second shot where you got the tops of the skyscrapers in focus, and use Helicon to combine them. Wouldn't this work? I don't see any particular reason to have to work front-to-back with Helicon. Bottom-to-top should work too, I would hope.
Probably worth a bash! Have yet to try it myself though.
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David,
Kudos and Respect to you for responding on this thread.
I have certainly learned some things about the limitations of my HC lenses, yet I continue to love them more every day, as I get to know them. (I have the same relationships like this with women -- at first I love ever trait, then I discover their shortcomings, while I, of course, remain perfect).
No disrespect meant toward Hasselblad whatsoever, but I must admit, my bubble was burst a small bit when I saw the small-aperture results. But mostly I felt like I had egg on my face for not doing this test about twenty-five years ago. I feel like a chump. (But maybe it was not so much an issue with EPR or any other 120 film).
I will zip the files and send them to you. There are five tests.
I've owned a million Hasselblads in my life, both 500 and 200, (and shot the 680 with Fuji lenses for twenty years too), so my respect for Hasselblad and Fuji is VERY high, (and continues to be).
If you only realised the issue after a 'test' was it really an issue at all?
...and I aim to please. ;-)
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I want to ask one final question here -- What about The F64 Group? Seriously. They prided themselves on tiny apertures, and unlimited depth of field, (pre-Photoshop). Were they the most misguided group ever, or was it truly a non-issue with film?
I think this is the crux of the matter. The lenses have actually got a lot better when you compare H system to V system. I shot V system for 15 years and loved it but the fact is I never looked at those (film) files at 100%. We were looking at film with what a 16X loupe? I cannot face the maths but would be willing to bet that looking at a 120 chrome with a 16X Schneider doesn't even come close to looking at a 30 something MP file at 100%. I pulled up a drum scan of a frame of EPP the other day and was shocked by the (poor) quality. I just don't think we ever knew.
Nick-T
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If you only realised the issue after a 'test' was it really an issue at all?
...and I aim to please. ;-)
Yes, it was an issue with a 120 Macro HC last month, on a tabletop shot.
If I ever track down your email address, I'll give you the details.
In the end, with enough Smart Sharpen it was fine, but I was nervous there for a while; thought I had a defective lens.
So yes, it's been an issue.
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I think this is the crux of the matter. The lenses have actually got a lot better when you compare H system to V system. I shot V system for 15 years and loved it but the fact is I never looked at those (film) files at 100%. We were looking at film with what a 16X loupe? I cannot face the maths but would be willing to bet that looking at a 120 chrome with a 16X Schneider doesn't even come close to looking at a 30 something MP file at 100%. I pulled up a drum scan of a frame of EPP the other day and was shocked by the (poor) quality. I just don't think we ever knew.
Nick-T
True. Expectations were probably just a lot lower and more realistic given the technology at the time. It simply wasn't possible to capture fine detail like we can today, diffraction or not. And like Jack said, things like halation and the quality of lenses at the time added up to a much lower image quality than what we're used to with modern photography, despite the fact that it was phenomenal for the time. They/we just didn't know any better.
Happens all the time. Vinyl vs. CD, 16mm vs. 4k RED ONE, CRT vs. LCD, and on and on. That mighty P65+ won't hold a candle to technology in 30-40 years, despite the fact that as professionals, we spend every waking minute improving our technique and pushing the quality limit.
EDIT: I realize some folks prefer film vs. digital, and vinyl vs. digital. There's always room for nostalgia and that little bit of unexplainable "style."
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Correct me if I am wrong, but it would seem to me that if you can orient the plane of sharpest focus so that it covers all moving elements, cars, people, etc., then you could do a second shot where you got the tops of the skyscrapers in focus, and use Helicon to combine them. Wouldn't this work? I don't see any particular reason to have to work front-to-back with Helicon. Bottom-to-top should work too, I would hope.
You can position a plane through any three points - but the limitations of the movements of any specific camera will limit how much you can move the Plane of sharpest focus - most of the modern compact view cameras limit you to 5 degrees tilt, and you need about seven to get the ground you are standing on (and the horizon) in focus with a 150 mm lens.
Where you need a short exposure to freeze waves in a seascape, (or cars, pedestrians etc.) and another shot for the cliffs beyond, (or buildings) yes, I am planing to combine shots vertically, or by differential focus using tilt rather than extension.
As you get a wedge of acceptable focus, you can often get tall, distant objects in focus, but, as I believe you are saying, you can use movements to allow you to use shorter exposures for moving objects near a plane.
This I took with the Hasselblad 50-110 zoom @ 65 mm, 1/20th f11... if the surf had been breaking, or I had wanted to freeze the people on the beech, or the vehicles, a view camera would have been useful.
[attachment=14403:Cornwall...Object_1.jpg]
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Dick, Port Izzac (sp?) looks as interesting as ever. Taken from the Doc's house?
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I want to ask one final question here -- What about The F64 Group? Seriously. They prided themselves on tiny apertures, and unlimited depth of field, (pre-Photoshop). Were they the most misguided group ever, or was it truly a non-issue with film?
Hi gwhitf, please see my response on post #37 of your thread. I show just what you ask about film.
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Nice! Can you post an example to show us how well it works --- with say the 100 focused on something relatively close, like at about 1 to 1-1/2 meters away, wide open and f5.6 or 8?
...but how would know where I focussed? You would have to trust me.
Essentially, the theory is simple. Aperture related focus shift is a known factor (if you are the lens designer) so can be corrected by a) knowing the working aperture and knowing the focus distance.
The H1 had two zones in the focus range which related to two different corrections for focus, in the H3D there are several more for greater accuracy.
We are talking bee's dick corrections but every little helps, especially (as I keep saying) as the resolution increases on digital sensors.
Best,
David
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Yes, it was an issue with a 120 Macro HC last month, on a tabletop shot.
If I ever track down your email address, I'll give you the details.
In the end, with enough Smart Sharpen it was fine, but I was nervous there for a while; thought I had a defective lens.
So yes, it's been an issue.
Sounds like you need an HTS?
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...but how would know where I focussed? You would have to trust me.
Essentially, the theory is simple. Aperture related focus shift is a known factor (if you are the lens designer) so can be corrected by a) knowing the working aperture and knowing the focus distance.
The H1 had two zones in the focus range which related to two different corrections for focus, in the H3D there are several more for greater accuracy.
We are talking bee's dick corrections but every little helps, especially (as I keep saying) as the resolution increases on digital sensors.
I understand the theory... What I am not so sure about is the implementation of said corrections
Oh, and I'd trust you Dave.
Cheers,
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I understand the theory... What I am not so sure about is the implementation of said corrections
Oh, and I'd trust you Dave.
Cheers,
Next time I have a 100 in my hands ill take a wide open and an f8 and we'll see.
Essentially the AF drive knows to + or - the setting based on working aperture set. Same goes for Manual Focus (if you are using the focus confirmation arrows in the VF) as these light up based on the same data from the AF system.
Thanks for the trust!
D
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But in general, my advice is to NEVER shoot an HC lens any smaller than f11. Even f16 shows noticeable softness, and 22 is a joke, and let's not even talk about 32 or 45.
I guess now we know why Michael did not use F22 when doing a quick comparison of the Canon G10 P&S and the P45+. The results might have enraged you all.
He used the P45+ at F11 and the G10 at F3.5. On A3+ size prints, both images looked virtually indistinguishable, except for the shallower DoF of the P45+, which sort of gave the game away.
I've always been a bit suspicious of the resolution of 8"x10" film when using F64, which gets you approximately the same DoF as 35mm at F8. I think it's understood that you cannot get tack sharp images at F64, even with Large Format. But what you do get with such a large format is better tonality, smoother gradations and far less grain. These qualities are sometimes more important than the ultimate in resolution.
It's also a fact that, whilst at F64 the plane of focus will not be as sharp as it would be at F22, the parts furthest away from the plane of focus will be far sharper at F64 than they are at F22.
In fact, the difference in sharpeness at the plane of focus, between F22 and F64, will be far less than the difference in sharpness away from the plane of focus, depending on the depth of the scene of course.
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Hi Ray,
You forget one important factor concerning lenses used for large format film: they have been built and optzimized for an optimal f-stop around 22. In fact, they give no noticeable difference (according to MTF curves) between f16 and f45, most of them. That is when used at infinity, on 4x5". Using a larger format, e.g. 8x10", an aperture of f64 is still within the limit (under) of the critical aperture where diffraction "circles" starts to be bigger than the allowed confusion circles and affecting the overall sharpness, at infinity. For sure, f64 is not in the optimal reproduction range of large format lenses, as you have said, but not that much of a problem when DoF is needed and not reachable with a plane adjustment.
Best regards,
Thierry
I've always been a bit suspicious of the resolution of 8"x10" film when using F64, which gets you approximately the same DoF as 35mm at F8. I think it's understood that you cannot get tack sharp images at F64, even with Large Format. But what you do get with such a large format is better tonality, smoother gradations and far less grain. These qualities are sometimes more important than the ultimate in resolution.
It's also a fact that, whilst at F64 the plane of focus will not be as sharp as it would be at F22, the parts furthest away from the plane of focus will be far sharper at F64 than they are at F22.
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Sounds like you need an HTS?
Mr G,
Can you confirm whether the HTS works with an H2/P45+ with the 35mm HC lens, even if some of the Pheatures were disabled?
Will it physically work, and take a photograph with an enemy back and a body that's been disowned?
Thanks.
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tis a fine balance - selling lenses and HTs's that work with competing backs on discontinued body strategy - I wonder at the economics of it all..given the stats on known sales and projected sales both segmented by camera in use type I could optimise your close out "the free loading competition totally" timing for you David. At a guess i'd suggest oh maybe another 18 months...
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You stop down, thinking you're going to carry focus deeper into the frame, when in truth, it's like you're laying a Gaussian Blur layer over the entire photograph. Even the subject area that you wanted tack sharp.
If focus stacking is too complicated due to the conditions but you have the time to shoot at least two shots you can shoot the first shot at f8 to get your main subject very sharp and a second shot at f16 for more DOF and merge the two shots in Photoshop.
So you take the f16 shot and add in the sweet spot of the f8 shot. That works very well and might be a good compromise in some situations.
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tis a fine balance - selling lenses and HTs's that work with competing backs on discontinued body strategy - I wonder at the economics of it all..given the stats on known sales and projected sales both segmented by camera in use type I could optimise your close out "the free loading competition totally" timing for you David. At a guess i'd suggest oh maybe another 18 months...
I agree with you. You can feel the battle lines being drawn -- and the only two armies will be Hasselblad and Phocus, marching face to face toward the PhaseOne/CaptureOne army, (with PFC Gomer Pyle Mamiya bringing up the rear). You can feel the showdown about to happen soon.
If I was a betting man, (and a working photographer), I'm putting my money on Hasselblad, long-term. They continue to refine, tweak, and add new features almost every few months, that apply to working photographers.
At some point, a man's gotta choose, and you can feel the two camps splitting more and more every day. I'm stuck right in the middle, with this mutant camera/back. I feel like I'm the child of Divorced Parents, and Mommy ain't talking to Daddy. I gotta go to Big Brother David or Big Brother Dougie to get any answers about the family.
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You forget one important factor concerning lenses used for large format film: they have been built and optzimized for an optimal f-stop around 22. In fact, they give no noticeable difference (according to MTF curves) between f16 and f45, most of them. Thierry
Thierry,
That sounds a bit odd to me. I cannot understand why a lens would have the same performance at F16 as at F45, unless it was a really lousy lens with lots of aberrations which were so bad that there's no difference between F16 and F45. In other words, at F16, all the other aberrations are greater than the diffraction effects. At F45, diffraction is greater than all the other aberrations.
Add the total aberrations, including diffraction, at F16 and at F45, then the sum is the same. You must be referring to some very old lens designs. No?
There are a few 35mm format zoom lenses which are sharpest at F16, usually at the long end. When a 35m lens is sharpest at F16, it's a sure indication it's a low quality lens.
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Dick, Port Izzac (sp?) looks as interesting as ever. Taken from the Doc's house?
Yes - Port Isaac, 20 or 30 meters below the Doc's House... and there are dozens of equally photogenic harbours, estuaries, bays etc. around the British coastline...
The pic is a compromise with:
not a short enough exposure to stop movement of waves, people and vehicles
not a small enough aperture for sufficient DOF
not a large enough aperture to eliminate diffraction
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Mr G,
Can you confirm whether the HTS works with an H2/P45+ with the 35mm HC lens, even if some of the Pheatures were disabled?
Will it physically work, and take a photograph with an enemy back and a body that's been disowned?
Thanks.
Yes George it will work. Obviously you won't get the distortion corrections and you'll have two carry two battery chargers for life but at least you won't have to learn Phocus
Nick-T
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Yes George it will work. Obviously you won't get the distortion corrections and you'll have two carry two battery chargers for life but at least you won't have to learn Phocus
Nick-T
Ouch. Below the belt.
Leaving for the desert next Wednesday. Will have to hire an extra Sherpa just to carry the required battery chargers for my broken-marriage system...
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Mr G,
Can you confirm whether the HTS works with an H2/P45+ with the 35mm HC lens, even if some of the Pheatures were disabled?
Will it physically work, and take a photograph with an enemy back and a body that's been disowned?
Thanks.
Yes it will work. You will need your H2 on the latest firmware mind. So send to NJ for update or find a friend with an ixpress or CF back and they can do it through Phocus.
David
Edit Ps. Oh didn't see Nick's reply. Thanks... and yes TWO chargers. Tsk tsk.
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I have to agree with Jack Flesher here.
Diffraction is a constant that varies only with aperture diameter. It exists to some degree at all apertures, in proportion to physical aperture diameter. It exists at F2.8, but is so small that it's irrelevant compared with diffraction effects at F16 which begin to rear their head.
Diffraction is something we can do little about. Its effects are proportional to F stop.
If a lens is sharpest at F5.6, it's because all the other lens distortions types have been reduced below the diffraction limit that applies to the aperture. (Is that clear, or is it gobbledegook?)
If a lens is sharpest at F16, (and some 35mm zooms are), it's because all the aberrations other than diffration, coma and astigmatism etc, are so lousy, that the lens is lousy.
Diffraction effects are completely embedded in the laws of Physics. But at F2.8 they're so small as to be insignificant.
At F16, resolution is limited by diffraction. One could say, all lenses are equal at F16, no matter how hard the lens designers work.
This is exactly why I use Leica glass on my Canon's - at f5.6 my Leica's are razor sharp from edge to edge at infinity. Past f11 (where my Canon zooms need to be), most 35mm glass gets diffraction softening. I would assume this applies to most new MF glass also because of the sensor quality. I just can't imagine software sharpening will make up for poor sharpness from the optics, but I guess it helps a bit.
There is no substitute for knowing what you are doing and using the appropriate f stop for ultimate image quality for each photograph.