Luminous Landscape Forum
Equipment & Techniques => Digital Cameras & Shooting Techniques => Topic started by: kat2290 on August 12, 2010, 04:36:01 am
-
Hi :)
So I've been trying to get to grips with the hyper focal method to improve front to back sharpness in my images. I have been using a chart to work out the distance and everything seems to be going fine. Apart from one thing! Once I'm all set up i.e tripod, cable release, mirror lock up etc. I compose the shot, and then I check my chart to see where I should be focusing. I usually shoot at F8 around 17mm so the distance would be 1.20metres...How do I then accurately focus 1.20metres away? I have a distance scale on my lens (it's a zoom lens so its not a 'proper scale' if you know what i mean? which I refer to but after the 1 metre mark on the scale it becomes difficult (for me anyway) to accurately determine where other distances would be on the scale. Is using the scale the most accurate way on focusing on something a particular distance away or is there another way of doing it?
Kat
-
If you are shooting 17mm at F8 then you are really just stressing yourself for nothing worrying about accurate Hyperfocal distance. As long as your focus point is at least 2m (just to be safe) from the front of the lens you will have infinite depth of field at F8 from roughly .75 of a metre to infinity.
In this example I would just focus roughly 1/3rd (or slightly before) into the frame (as is good practice) and everything will be tack sharp.
Personally, I find hyperfocal distance more useful at the telephoto end where DOF is much narrower.
You dont say what your camera is - but if you have life view, then use it to select a point roughly a third into the frame, zoom in 10X (or as much as possible) and get critical focus that way - stop to F8 and you will get great results.
Give the above a try - you wont be disappointed with the results.
-
I'll not completely agree with Josh-H : beware that an hyperfocal calculation may well decrease your sharpness, especially at infinity...
Focusing at 1.20m at 17mm f/8 will give you at infinity a blur circle about 30µm on the sensor, ie a blur extending on about 4 or 6 pixels depending on the camera you use. Would you call that "tack sharp"?
Moreover, blurs always add to each other ; in other terms, even if the defocusing blur circle is a bit smaller than the pixel pitch, you may still see some small loss of sharpness relative to the perfect, in-focus zone (this especially if you shoot with a very sharp lens and/or a sensor with weak or inexistant AA filter and print big, so we may count how many angels can sit on the top of a microlens here).
That said, some small "differential sharpness" may be quite efficient to separate a foreground subject from its still-readable background, adding a tad of that much-praised "3d look" to your image.
For me who am affected with a bit of myopia, the contrary (blurred foreground, sharp background) is not as efficient, but your myopia may vary - and I'd say giving the maximal sharpness to the main subject may be the most efficient strategy in most cases.
Bottom lines :
- don't ever expect the result of an hyperfocal calculation to be equally sharp, especially if you take into account the 30µm circle of confusion dating of the middle of last century,
- focusing on a physical subject rather than on a calculated distance may be first easier and second prettier,
- to gauge the effect on a print, carefully inspect the print itself, taking into account the subject matter.
-
Most good hyperfocal calculators will allow you to specify the circle of confusion. .30 is too high. For a cropped sensor camera, I use .19. I arrived at this number with some gross experimentation, so don't take it as gospel.
As for how to focus at a specific distance...I don't use the markings on the lens barrel. I generally pick an object that is approximately the correct distance away and use the AF button to focus on that--generally erring on objects closer rather than farther because infinity is never really that focused (distance, haze, etc...). Then I recompose and shoot my shot.
As others have pointed out, using hyperfocal distances in your photography is a good idea, but it is a compromise. Theoretically, your best focus will be achieved in a very narrow focal plane at your widest aperture. As you stop down the aperture, you are decreasing the focus acuity at the focus plane and averaging the focus quality across a wider depth of field. For this reason, I rarely shoot at f/22. The averaging affect of the focus makes the image look garbled to me.
For any lens, you should do some experiments to determine what the aperture has the best performance, then using that aperture, look at your hyperfocal calculator and consider the key subject matter in your shot before choosing where to focus. They hyperfocal calculator simply helps you avoid (or in some situations maximize) wasting good depth of field outside the image capture area.
-
You need to read Merklinger's "the ins and outs of focus"
-
You need to read Merklinger's "the ins and outs of focus"
+1 I've seen several tests of both methods and Merklinger always wins :)
-
I'll not completely agree with Josh-H : beware that an hyperfocal calculation may well decrease your sharpness, especially at infinity...
Focusing at 1.20m at 17mm f/8 will give you at infinity a blur circle about 30µm on the sensor, ie a blur extending on about 4 or 6 pixels depending on the camera you use. Would you call that "tack sharp"?
Moreover, blurs always add to each other ; in other terms, even if the defocusing blur circle is a bit smaller than the pixel pitch, you may still see some small loss of sharpness relative to the perfect, in-focus zone (this especially if you shoot with a very sharp lens and/or a sensor with weak or inexistant AA filter and print big, so we may count how many angels can sit on the top of a microlens here).
That said, some small "differential sharpness" may be quite efficient to separate a foreground subject from its still-readable background, adding a tad of that much-praised "3d look" to your image.
For me who am affected with a bit of myopia, the contrary (blurred foreground, sharp background) is not as efficient, but your myopia may vary - and I'd say giving the maximal sharpness to the main subject may be the most efficient strategy in most cases.
Bottom lines :
- don't ever expect the result of an hyperfocal calculation to be equally sharp, especially if you take into account the 30µm circle of confusion dating of the middle of last century,
- focusing on a physical subject rather than on a calculated distance may be first easier and second prettier,
- to gauge the effect on a print, carefully inspect the print itself, taking into account the subject matter.
I fully agree with Nicolas.
Most criticism about hyperfocal calculations is not founded, it usually comes down to improper use of the method. Unlike film, digital sensors have a hard limitation of maximum resolution, namely the sensel size. Detail cannot be sharper than the sensel size. When using that sensel size, or rather the sensel pitch, as a COC criterion, then nothing can be sharper, even at the horizon. When the COC is set to the sensel pitch, then the hyperfocal blur circle at infinity will be exactly the size of one sensel.
Nicolas is correct that lens blur and the diffraction blur add (their MTFs multiply), but there is some leeway due to the AA-filter and the Raw conversion process, and the overpowering effect of defocus on the combined system MTF. In my experience a COC of 1.5x the sensel pitch will not produce visible blur, especially after proper sharpening. With advanced (deconvolution) sharpening one might push it a bit further, but my rule of thumb of 1.5x sensel pitch works fine for me with the planning of a shoot. It also tells me, should maximum DOF sharpness be needed, at which distances I need to focus for focus stacking). BTW, there is also a rule of thumb for the aperture number that produces a diffraction blur of 1.5x the sensel pitch. Just take the sensel pitch expressed in microns, and multiply that by a factor of 1.108, and the aperture number is the result. So a 6.4 micron sensel pitch camera will start to suffer from visible loss of microdetail (at the pixel level!) at apertures narrower than f/7.1. How much of that loss of microdetail at the pixel level is still tolerable is a matter of personal choice. Perhaps the image will not be blown up to huge proportions, in which case the overall DOF effect becomes more important than pixel accurate microdetail.
Then focusing at the indicated distance(s), either manually (for focus stacking where the camera shouldn't move) or with AF will work fine, although at larger distances it's still a bit of a guess (unless you use e.g. a laser distance finder).
Having said all that, there can be a clear benefit to just focusing on the main subject, and letting the DOF fall where it does, but that depends on the scene at hand, and the output size.
Cheers,
Bart
-
There's a very good article on focusing right here on LL (http://www.luminous-landscape.com/tutorials/Digital%20Focusing.shtml), light on technical jargon but high on application is.
I use Liveview to focus. I understand it's the most reliable way to focus when you're on a tripod and not in a hurry - someone correct me if I'm wrong. I just put the focus point on whatever I want to be in focus, taking into account the teachings from the article above.
edit: it seems to be based on Merklinger's article mentioned above! Given Merklinger's article, how does sensor size enter the rule-of-thumbs? ie. I use 1.6 and 2.0 crop factor digital cameras, and MF and LF film cameras - are the lens focal lengths to be converted to 35mm format equivalents?
Also, from the conclusion of Merklinger article:
For typical normal and wide-angle lenses, especially lenses having focal lengths less than about 50 mm no matter what the camera format, set the lens opening to somewhere in the 2 mm to 5 mm range, set the focus at infinity, and shoot. For lens openings larger than 5 mm, and for longer lenses that tends to mean all normal working f-stops, focus on what is critically important. The same is true of close-up photography no matter what the lens.
(emphasis mine) How do I determine the size of the lens opening?
-
Here's a less 'drastic' approach than Merklinger's infinity focus:
http://www.normankoren.com/Tutorials/MTF6.html#Hyperfocal
From the above Norman Koren link:
"If the part of the scene at infinity is at all important in the image— it's often visually dominant— you'll be disappointed with the sharpness, which is only 40% that of a high quality lens in focus; about one third what the eye can distinguish. Merklinger recommends focusing at infinity— you lose very little forward depth of field. I feel safe setting infinity focus opposite the far DOF mark corresponding to 2 stops larger than the actual f-stop setting (half the number). For example, if you are using f/8, it's safe to put the far f/4 DOF mark opposite infinity. It's a judgment call. When you make it, think about what parts of the image will be dominant. There is no rule to blindly follow. "
-
I am not sure this is responsive to your question. But I use the 5Dii which offers a live view display of the image. The importance of this feature for landscape photography has not been fully appreciated by most of the reviewers. One uses manual focus and a tripod.The mirror is automatically locked up by pushing the LV button (Michael, did you hear that? Canon responded to your complaints :~] ). In live view with exposure simulation mode one has a real-time histogram and the ability to explore the image focus at 5x or 10x magnification. This allows one to gauge the depth of field and get optimal focus. I say optimal focus because it eliminates the cameras focusing system; one sees the image derived directly from the sensor; focus points don't matter. It's slow but sure. I have my jpeg parameters turned down to neutralize the display - no sharpening and low saturation. This results in a reasonably accurate real-time histogram, meaning I can expose to the right with confidence. Live View is the digital equivalent of the ground glass and focusing cloth, except the image is right side up.
Hope this is useful to you.
-
Also, from the conclusion of Merklinger article:
(emphasis mine) How do I determine the size of the lens opening?
Since: f number = focal length/aperture diameter you can solve the equation for diameter.
e.g.
Where f = f number, L = focal length and d = aperture diameter, then
diameter d = L/f. For a 50mm lens at f/8 the diameter would be d = 50/8 = 6.25mm.
-
Interesting reading. I think this is exactly the kind of discussion that gives the LL fora the reputation as being the place for the measurbators to hang out on the web. ;)
-
Since: f number = focal length/aperture diameter you can solve the equation for diameter.
e.g.
Where f = f number, L = focal length and d = aperture diameter, then
diameter d = L/f. For a 50mm lens at f/8 the diameter would be d = 50/8 = 6.25mm.
Thanks!
Interesting reading. I think this is exactly the kind of discussion that gives the LL fora the reputation as being the place for the measurbators to hang out on the web. ;)
It's all fun and games until someone gets an irredeemably out-of-focus shot of Elvis.
-
Hi,
Since upgrading from 135 to MF and than full frame digital I essentially have found that there is essentially no depth of field. The only thing that gets really sharp is what you focus on.
In essence I also found that it is also reasonable to stop down to f/16, going beyond that we start to loose a little bit to much.
So my experience is:
- Focus on what's important
- Stop down if needed
- Hope for the best
Best regards
Erik
-
Hi,
Since upgrading from 135 to MF and than full frame digital I essentially have found that there is essentially no depth of field. The only thing that gets really sharp is what you focus on.
In essence I also found that it is also reasonable to stop down to f/16, going beyond that we start to loose a little bit to much.
So my experience is:
- Focus on what's important
- Stop down if needed
- Hope for the best
Best regards
Erik
This is the argument for:
Medium Format Digital View Cameras - you can control the position of the plane of sharpest focus
and Focus stacking.
f8 works for 2d subjects, but for heads and other 3d objects, f16 works better!
-
Thanks!
It's all fun and games until someone gets an irredeemably out-of-focus shot of Elvis.
Maybe that would be a blessing in disguise?
Rob C
-
Thanks!
It's all fun and games until someone gets an irredeemably out-of-focus shot of Elvis.
Hey! then we could go over to that de-convolution discussion and see if we can de-convolute Elvis back :)
-
That is quite an interesting discussion.
Do you know if for FF cameras the circle of confusion is the same as for film? ie 0.03mm?
When I finally get some time I am planning to run some test comparing the WA approach to hyper-focal focussing at smaller apertures (f8-f16) for my own use.
-
That is quite an interesting discussion.
Do you know if for FF cameras the circle of confusion is the same as for film? ie 0.03mm?
When I finally get some time I am planning to run some test comparing the WA approach to hyper-focal focussing at smaller apertures (f8-f16) for my own use.
Unless you don't plan on printing any larger than 8x10 inches you do NOT want to use 0.03mm for a FF DSLR. That CoC is even too large for film and goes back many decades to the days when 8x10 was considered a large print. Lens manufacturer's just stuck with the old ~-.03 mm value even as film and digital resolution increased along with print size.
If no one else responds I'll post some useful references for you (which I don't have access to at the moment) but recommendations for DSLR are sometimes 1 to 1.5 x the pixel pitch. For a Canon 5D II I think that works out to approx 1.5 * 6micron = 0.009 mm. I think some would argue this is too aggressive and you could consider an alternative calculation based on the largest print size you want to make and how close you want a person with normal vision to peer at it. As I recall (I'll check reference later) for a 24 x 36 inch print viewed from 20 inches (pretty close) the CoC would need to be 0.016 mm.
-
Do you know if for FF cameras the circle of confusion is the same as for film? ie 0.03mm?
It may be the same as for fine grained and sharp (B&W) film, but definitely not 30µm.
1 to 2 pixels is a good starting base ; the best is to see for yourself.
-
Hmm. At the moment my only worry is that some of the pictures will end up being printed as 18x12" minimum. Obviously, for GPx ;) panoramas I go bigger.
KenS, I would really appreciate the links or any info on how to work this out to get the best results.
-
rags DOF calculator (http://www.rags-int-inc.com/PhotoTechStuff/DoF_Calculator/DoF_Calculator.html)
Is the best I have found... they include a link to DOF on Wikipedia which quotes three different formulae for DOF, for normal, close-up and Macro photography. There is so much nonsense written about DOF, but much of it is OK for standard amateur or DSLR expectations.
With rags DOF calculator (http://www.rags-int-inc.com/PhotoTechStuff/DoF_Calculator/DoF_Calculator.html) you can specify any sensor size, but I think that if you specify 645 it assumes you are using film, and you need to specify the circle of confusion.
I seems that for 645 6 micros sensors 10, 20 or 30 micron CoF is OK for critical focus staking to hand-held portraiture... For a head shot, 20 or 30 microns gives enough DOF at 645/110mm/f16, and this gives good results in practice.
With most "normal" cameras, I think the Anti-Aliasing filter limits the CoC to about three times the pixel pitch, so 20 microns would be OK for a 6 micron FF 24 * 36mm sensor.
Most of what has been written about DOF does not seem to take into account that some of use large, high-res cameras because we want to be able to print large, but with res than can be appreciated from 250mm.
There are similar formulae in Merklinger's books, but they are confusing.
-
Most of what has been written about DOF does not seem to take into account that some of use large, high-res cameras because we want to be able to print large, but with res than can be appreciated from 250mm.
And there, in all of this, is the crux of the issue. All of this hand wringing about DOF, whether hyperfocal focusing is the right approach, whether focusing at infinity is the right approach, CoC size, really means nothing in 99.9999999999999999999999999999999999999999..............................% of cases. We're talking about micrometers of difference at the sensor/film plane and in a print. The only time this really matters, within reason, is when idiots like alleged photographers stick their noses right on a print or pixel peep at 300% on a computer screen. At normal viewing distances these things are indistinguishable. Yes, a very trained eye might be able to tell the difference (big stress on might) a certain, small percentage of the time but the vast majority of people won't be able to. The vast majority of seasoned art buyers won't be able to. This kind of discussion really is the purview of the internet photo forum and has little to no relevance or applicability in the real world.
For those who don't do metric, 250 mm is 25 cm which is 10". No one, except pixel peepers, is going to spend much, if any, time looking at a 20x30 print from 10". Combine that with the distortions that putting the print behind glass or acrylic bring in and the even worse distortions that a good deal of the anti-glare glass or acrylic bring in, couple that with the softness created by a number of the printing media available on the market today (e.g., velvet papers, watercolour papers, heavily textured rag papers, canvas) and the relevance of this type of discussion becomes increasingly less at an increasingly rapid rate.
-
The only time this really matters, within reason, is when idiots like alleged photographers stick their noses right on a print or pixel peep at 300% on a computer screen. At normal viewing distances these things are indistinguishable.
Some 24 * 48" picture would be observed from 48" or more... but, in a village scape people might look at individual houses or people, and in a group photo you would be looking at individuals... and it is nice to be able to produce a half reasonable A4 (10 * 8 ) picture of anyone in the group.
Many weddings are the last occasion at which an elderly relative is photographed dressed-up.
-
and it is nice to be able to produce a half reasonable A4 (10 * 8 ) picture of anyone in the group.
That's got more to do with format and how much you can crop and still have enough film or pixels than it does with DOF.
-
and it is nice to be able to produce a half reasonable A4 (10 * 8 ) picture of anyone in the group.
That's got more to do with format and how much you can crop and still have enough film or pixels than it does with DOF.
It is not all about pixel count... there is little benefit in having enough pixels if you have too little DOF, and some heads in the group are OOF.
-
I said 'more about', not 'all about'.
And, quite frankly, if someone can't figure out how to get DOF right with a group photo without resorting to plugging micrometer measurements into a Cray supercomputer then they should probably step out from behind the camera.
-
I said 'more about', not 'all about'.
And, quite frankly, if someone can't figure out how to get DOF right with a group photo without resorting to plugging micrometer measurements into a Cray supercomputer then they should probably step out from behind the camera.
A view camera would work better, and let you get all the heads in the plane of sharpest focus, and allow for sharp focus on any decorative stonework above and behind the group.
-
I wrote earlier in this thread about a practical solution to this problem. It landed with a thud; no one took notice. If I were shooting the group photo with my Canon 5dii I would select an appropriate lens, maybe the 24-105, 0r 24-70, mount it on my tripod and set the camera to live view. Take special note, I AM NOT TALKING ABOUT AUTO FOCUS WITH LIVE VIEW. Then one makes a trial focus, say on a face in the middle of the group. The focus is effected manually with live set to 10x, effectively set at the single pixel level. Then, with the live view mode set to to exposure simulation, you push the dof preview button, the camera adjusts the screen brightness (you will be able to see the image clearly), and you can explore the dof, moving the focal area with the joy stick. You may wish to select a different point of focus to optimize for your composition, or set a smaller aperture, etc. As I said before, this is the modern equivalent of the view camera's ground glass and focusing cloth, only the image is right side up. The charm of this procedure is that the autofocus mechanism of the camera is eliminated; you are looking at a rendering of the image directly from the sensor; you have, in addition, a real-time histogram. You will be amazed how much sharper your images can be with this technique. Lenses you thought were soft may be resurrected when focused using live view.
-
How long does all that roaming around at 10x magnification take? Focus here, press this button, shift around over there, re-adjust, reset, work that setting. Might be OK for a landscape or other static scene (e.g., architecture) where no one is going to get impatient but if someone were farting around with the camera, futzing with this and that for more than about 5 seconds and I were in the group, I'd say screw it and walk away. Even with architecture, if I'm at a client location they want me in and out as quickly as possible. Wasting their time by screwing around with the camera isn't going to make them overly happy.
Dick, you're right. It would. ;D
-
A view camera would work better, and let you get all the heads in the plane of sharpest focus, and allow for sharp focus on any decorative stonework above and behind the group.
Dick, you're right. It would. ;D
Thanks, Bob...
I am seriously thinking about this... I could set the camera up in advance, and use a pole or two to indicate the position of the POS, so arranging the heads in the POS would not be difficult or time-consuming... need to try it on a camera club or some of my relatives first.
-
I am seriously thinking about this... I could set the camera up in advance, and use a pole or two to indicate the position of the POS, so arranging the heads in the POS would not be difficult or time-consuming... need to try it on a camera club or some of my relatives first.
Hi Dick,
That would work, although one could pre-compute the tilt angle needed for certain angles (e.g. stair steps often have a common slope, or a ladder has a known height) and then all that's needed is focus. Of course, more difficult setups (e.g. cresent shaped groups ) require more difficult calculations ... Setting up things prior to the group's arrival is the easiest approach in difficult settings anyway.
Cheers,
Bart
-
Hi Dick,
That would work, although one could pre-compute the tilt angle needed for certain angles (e.g. stair steps often have a common slope, or a ladder has a known height) and then all that's needed is focus. Of course, more difficult setups (e.g. cresent shaped groups ) require more difficult calculations ... Setting up things prior to the group's arrival is the easiest approach in difficult settings anyway.
Cheers,
Bart
Yes, thanks, Bart.
If part of the object of the operation is to get something above and behind the group in focus, you measure the distance from the camera to it, and it's height above the ground... pick a line on the ground where the POS passes through and do a little Merklinger geometry to calculate J, the distance below the lens of the POS, and you can then calculate the tilt angle with trig - no Cray required, I would do it on the laptop or with an excel spreadsheet on my mobile phone, and I think it would produce a significantly better result, especially if the detail above and behind could put the picture in context with the venue.
If I was working rectilinearly I would arrange the group straight, if I wanted a crescent shaped group I might consider pan-and-stitch, but that might be a PITA with wedding guests.
-
Hi,
My experience is that with full format on hi res DSLR depth of field is an issue even at relatively large distances. If you need to enlarge (like making A4s of individuals in a group) you would need all the sharpness you can have at the pixel level. There is nothing illegitimate looking at fine detail in a large enlargement.
I got confronted with this when I went from 135 to MF in the film days. My prints were simply not sharp. I didn't go to MF to have 1/15 mm of COC but to achieve better sharpness than with 135. So I learned not to trust DOF scales.
Another way to see it is that you invest in a certain number of megapixels, especially if you buy a high end MFDB. So you pay something like extra 20000 USD for a 60MP back over a 30MP back (or so). Do you really want to throw away all those pixels?! You may not need them, of course, and there are a lot of other ways of wasting perfectly fine pixels:
- No tripod
- No MLU (Mirror Lock Up)
- Sloppy focus
- Stopping down beyond optimum
- Uncalibrated autofocus
Best regards
Erik
-
So you pay something like extra 20000 USD for a 60MP back over a 30MP back (or so). Do you really want to throw away all those pixels?! You may not need them, of course, and there are a lot of other ways of wasting perfectly fine pixels:
- No tripod
- No MLU (Mirror Lock Up)
- Sloppy focus
- Stopping down beyond optimum
- Uncalibrated autofocus
Best regards
Erik
We have gone back nearly 100 years to the "hand or stand" cameras that used the new fast 5 * 4" sheet film that was so fast that you could use the camera hand-held, if you were lucky.
It is difficult trying to get hand-held ambient MFD head-shots to look better than what you could do with 35mm, but I do not have a 35mm FF DSLR, so it does not stop me trying... to get adequate DOF you need f16, so you are starting to get diffraction, then you need to crank up the ISO as a compromise to reduce the effect of camera shake...
-
Hi,
My point is just that extracting the maximum resolution from any equipment demands careful work. I also assume that those who are willing to invest a serious amount of money in high res equipment, like the P65+, would expect the system to resolve optimally. It seems that resolution comes at a premium price. There are plenty of lower resolution digital backs, a few more affordable. But anyone investing in the P65 over a lesser MFDB is probably striving for resolution.
MFDB´s are claimed to have many advantages. The top of the line backs have higher resolution and larger sensor surface. So you are paying a lot for those advantages, but at least the resolution is easy to loose. Just stop down to f/22 and much is gone!
Best regards
Erik
-
Hi,
My point is just that extracting the maximum resolution from any equipment demands careful work. I also assume that those who are willing to invest a serious amount of money in high res equipment, like the P65+, would expect the system to resolve optimally.
Please note Like the H4D-60
You would like to imagine that people buying advanced amateur or professional equipment would have some idea how to get the quality they have paid for... but, in the real world, even some pros might imagine (initially) that a £30,000 camera will take a better picture than a £7,000 camera, regardless of the light or anything else.
MFDB´s are claimed to have many advantages. The top of the line backs have higher resolution and larger sensor surface. So you are paying a lot for those advantages, but at least the resolution is easy to loose. Just stop down to f/22 and much is gone!
Best regards
Erik
The larger sensor area reduces DOF, so it is not necessarily an advantage in all situations, so you use a smaller aperture to get back the DOF and loose the res through diffraction, and (if shooting hand-held) through camera shake,,, and do you lose less if you up the ISO to enable you to use a higher speed with a small aperture?
Even the old, low-res Hasselblad MFD's can use all the advantages of Phocus, and will make FF 35mm DSLR's look sick, if used well on a tripod or with flash.
The usual wisdom is that anyone with an expensive camera is an idiot:
... for having spent a great deal of money on kit that will not produce (proportionately) better results
... for having kit that they are not clever enough to use to it's full potential
Some people just make excuses because they are jealous... or they think there is no justice in the world as they think they could make better use of the kit. ...but, if you gave them the opportunity to use 60Mpx kit, you might not get it back in serviceable condition.
-
I have been using a program on my pocket pc for focus based on Merklingers work available here http://www.dl-c.com/PPC/#DOF 1.0
-
I have been using a program on my pocket pc for focus based on Merklingers work available here http://www.dl-c.com/PPC/#DOF 1.0
I think the Merklinger formulae are the same as those on Wikipedia, and I have programmed one or two f them into excel on my Mac, and transferred it to my mobile phone...
...have you only included the "landscape" formulae. or the macro formulae as well?
...do you have an excel version?
-
Dick,
This program was made available by Jonathan Sachs at Digital Light and Color. I didn`t write it-just used it with excellent results.
-
Here is another focus technique from Merklinger:
If the smallest object in the scene is 2 mm wide, such as a blade of grass, divide the focal length by 2 to get the aperture then focus at infinity. So if you are using a 35mm lens you divide by 2mm = about f16 then focus at infinity and all will be in focus.
-
Here is another focus technique from Merklinger:
If the smallest object in the scene is 2 mm wide, such as a blade of grass, divide the focal length by 2 to get the aperture then focus at infinity. So if you are using a 35mm lens you divide by 2mm = about f16 then focus at infinity and all will be in focus.
I believe in Merklinger's theory of focusing far rather than near, but this in a pretty useless theory for 300mm digital lenses, when diffraction kicks in at about f16!
-
I believe in Merklinger's theory of focusing far rather than near, but this in a pretty useless theory for 300mm digital lenses, when diffraction kicks in at about f16!
I've also had mixed success applying his methods to small sensors (APS-C and MFT). I should do some more testing, though. I've only tested at relatively short focus distances in the city, 5-50 meters. Results might be different with landscape photography.
-
Hi,
In my view the only method which works really well with longer lenses is focus stacking. The reason is mainly that with digital the area of critical focus is very small. That is not really depending on digital, it's just that higher precision is possible.
I have a small article on different methods here:
http://echophoto.dnsalias.net/ekr/index.php/photoarticles/29-handling-the-dof-trap
Perhaps it may be useful.
Best regards
Erik
I've also had mixed success applying his methods to small sensors (APS-C and MFT). I should do some more testing, though. I've only tested at relatively short focus distances in the city, 5-50 meters. Results might be different with landscape photography.
-
In that case the program for the pocket pc would work fine. I used it with my 70-210 lens at the long end and I really liked the results.
-
Hi,
In my view the only method which works really well with longer lenses is focus stacking. The reason is mainly that with digital the area of critical focus is very small. That is not really depending on digital, it's just that higher precision is possible.
I have a small article on different methods here:
http://echophoto.dnsalias.net/ekr/index.php/photoarticles/29-handling-the-dof-trap
Thanks. I might need to check out focus stacking for some subjects. DOF is helped by the smaller sensors I generally use, but there are some (film) MF and LF scenes which require pretty involved approach to get acceptable DOF. I still haven't nailed it despite using Cambridge in Colour's excellent DOF calculator in the past, which takes print size into account. Finding the sweet spot between diffraction and acceptable focus requires quite a bit of planning, previsualization and calculations, some which are not feasible in the field (unless someone knows a full-featured DOF and diffraction calculator for Android phones). Focus stacking is probably not feasible due to cost with LF, unless there are clear planes of focus like in your distant mountain example.
Also, Rome had at least four cinematographers (http://www.imdb.com/title/tt0384766/fullcredits).
-
Hi,
With large format you can probably stop down a lot. Film is less flat than sensors and large format lenses don't resolve as high as lenses for smaller formats, at least in general. In large format you also can use Scheimpflug with ease. Scheimpflug does not really increase DOF just changes the plane which is in focus.
Some LF cameras (like Sinar) have a Scheimpflug calculator built in, BTW.
Best regards
Erik
-
Thanks. I might need to check out focus stacking for some subjects. DOF is helped by the smaller sensors I generally use, but there are some (film) MF and LF scenes which require pretty involved approach to get acceptable DOF. I still haven't nailed it despite using Cambridge in Colour's excellent DOF calculator in the past, which takes print size into account. Finding the sweet spot between diffraction and acceptable focus requires quite a bit of planning, previsualization and calculations, some which are not feasible in the field (unless someone knows a full-featured DOF and diffraction calculator for Android phones). Focus stacking is probably not feasible due to cost with LF, unless there are clear planes of focus like in your distant mountain example.
The Rags DOF Calculator (http://www.rags-int-inc.com/PhotoTechStuff/DoF_Calculator/DoF_Calculator.html) tells you the size of the Airy disc (the COC that diffraction limits you to) so you can work it out... to focus from 30m to 400m @ f8 with COC = 0.01 you need to stack about 8 images... and this is the street outside my house, not a hypothetical situation.
All the formulae are available in Merklinger or on Wikipedia, and I can create an Excel spreadsheet on my laptop and download it into my Nokia phone - can you not do that with yours?
I ignore print size when taking photographs, as I might want to print it 6 foot tall, and my standard print size is 18 * 24" @360 ppi.
-
The Rags DOF Calculator (http://www.rags-int-inc.com/PhotoTechStuff/DoF_Calculator/DoF_Calculator.html) tells you the size of the Airy disc (the COC that diffraction limits you to) so you can work it out... to focus from 30m to 400m @ f8 with COC = 0.03 you need to stack about 8 images... and this is the street outside my house, not a hypothetical situation.
All the formulae are available in Merklinger or on Wikipedia, and I can create an Excel spreadsheet on my laptop and download it into my Nokia phone - can you not do that with yours?
I ignore print size when taking photographs, as I might want to print it 6 foot tall, an my standard print size is 18 * 24" @360 ppi.
Yeah, I've used the same DOF calculator, and while clunky it has some of the best feature sets available.
I have an Android phone which has a pretty good Photo Tools (http://hcpl-android.blogspot.com/2010/05/free-android-app-photo-tools.html) app, which allows for customized CoC, among other things. I've added a setting for 4x5" LF printed at 20x24", for example. It doesn't have a diffraction calculator, but the thresholds are pretty easy to memorize.
It would be nice if someone would program an all-inclusive DOF calculator, which would take everything from aperture, focal length, sensor size/film format, diffraction and print size/viewing distance into account, without having to use different calculators for them.
-
I believe in Merklinger's theory of focusing far rather than near, but this in a pretty useless theory for 300mm digital lenses, when diffraction kicks in at about f16!
Hi Dick,
With all due respect but Merklinger is wrong, when we're talking about digital sensors.
It is impossible to distiguish a focused infinity from a defocused infinity as long as the blur diameter of the infinity defocus is smaller than the sensel. In fact one is unlikely to see any difference, especially with a sensor array that's fitted with an AA-filter, when the blur diameter is less than 1.5x the sensel pitch. All one needs to do is use that as the COC criterion for the hyperfocal distance calculation.
The discussion usually comes from using too large a COC. Of course with film this becomes a different issue, and Merklinger is correct.
Cheers,
Bart
-
It would be nice if someone would program an all-inclusive DOF calculator, which would take everything from aperture, focal length, sensor size/film format, diffraction and print size/viewing distance into account, without having to use different calculators for them.
Hi Harri,
There is such a tool (http://toothwalker.org/optics/vwdof.html), unfortunately only available for Windows. It's customizable, can output tables, or compare different scenarios, and it displays the blur diameter at infinity, or for an object at a given distance from the focus plane.
The recommended COC for a given print viewing distance is given in the PDF that goes with the application, and is very simple to compute. One only needs to make a note of some viewing situations (but remember that people tend to walk up to the image for close inspection, if possible), and plug those values into the calculator. You can even use a couple of COCs side by side.
I wouldn't mind programming something myself (and I probably will), but it would also be Windows only (Mac is too much of a hassle, and would require an investment on my part).
Cheers,
Bart
-
Hi Dick,
With all due respect but Merklinger is wrong, when we're talking about digital sensors.
It is impossible to distiguish a focused infinity from a defocused infinity as long as the blur diameter of the infinity defocus is smaller than the sensel. In fact one is unlikely to see any difference, especially with a sensor array that's fitted with an AA-filter, when the blur diameter is less than 1.5x the sensel pitch. All one needs to do is feed that as the COC criterion for the hyperfocal distance calculation.
The discussion usually comes from using too large a COC. Of course whith film this becomes a different issue, and Merklinger is correct.
Cheers,
Bart
What you say is correct, and I appreciate that Merklinger's examples refereed to film, but what does Merklinger say that you think is incorrect? I merely mentioned his books as a source where the formulae could be found.
For critical stacking work I would use COC of 10 (about 1.5 time sensel pitch).
For snapshots I would use 30, and I do not use anything with an AA filter.
At f22 the Airy Disc is 30ish... for hand-held work I think, on balance that f16 (or f22) is a good compromise, depending how well the camera performs at High ISO.
-
Hi Harri,
There is such a tool (http://toothwalker.org/optics/vwdof.html), unfortunately only available for Windows. It's customizable, can output tables, or compare different scenarios, and it displays the blur diameter at infinity, or for an object at a given distance from the focus plane.
The recommended COC for a given print viewing distance is given in the PDF that goes with the application, and is very simple to compute. One only needs to make a note of some viewing situations (but remember that people tend to walk up to the image for close inspection, if possible), and plug those values into the calculator. You can even use a couple of COCs side by side.
I wouldn't mind programming something myself (and I probably will), but it would also be Windows only (Mac is too much of a hassle, and would require an investment on my part).
Cheers,
Bart
That's a pretty good program, thanks. Doesn't have a diffraction warning, though, and an integrated CoC calculator would also be useful - I dno't trust any baked-in CoC figures as they often rely on decades-old standards (small prints).
-
That's a pretty good program, thanks. Doesn't have a diffraction warning, though, and an integrated CoC calculator would also be useful - I dno't trust any baked-in CoC figures as they often rely on decades-old standards (small prints).
There is a simple calculation possible for diffraction (assuming green light of 555nm). When one takes 1.5x the sensel pitch as one's guideline, then 1.108x the sensel pitch in microns give the widest aperture value at which diffraction becomes visible (so just adding 10% and rounding up is easy enough to do by head). For a guideline of 1x the sensel pitch it would become a factor of 0.738x sensel pitch (subtract 1/4 of the sensel pitch in microns) for the onset of visible diffraction.
There is no explicit diffraction warning (because it's wavelength dependent), but once one takes the sensel pitch (or 1.5x the sensel pitch) criterion as calculated above as a guideline, then it's easy enough to see if the blur (either infinity or POI) exceeds that. The 'Options|COC criterion' menu choice (e.g. critical) for a given recording format, gives a very good starting point.
Besides, if an 8x10 in (~20x25 cm) print looks good at normal viewing distance (say 10-12 inches, 25-30 cm), then it will look good at any viewing distance provided that the viewing distance scales proportionally with the output size. Of course for close inspection, only pure resolution will survive scrutiny.
Cheers,
Bart
-
Besides, if an 8x10 in (~20x25 cm) print looks good at normal viewing distance (say 10-12 inches, 25-30 cm), then it will look good at any viewing distance provided that the viewing distance scales proportionally with the output size. Of course for close inspection, only pure resolution will survive scrutiny.
Good point - but many insist on sticking their nose to the print no matter how big is it :P
-
...if an 8x10 in (~20x25 cm) print looks good at normal viewing distance (say 10-12 inches, 25-30 cm), then it will look good at any viewing distance provided that the viewing distance scales proportionally with the output size. Of course for close inspection, only pure resolution will survive scrutiny.
Cheers,
Bart
Some people buy big cameras to make big prints (not just for weight training), so if my sensor is N times bigger than 24 * 36mm, I want to be able to make prints 3N times bigger than you could with a 24Mpx 24 * 36mm sensor with an Anti-Aliasing filter.
I want people to be draw in to my pictures (and not just ignore them and walk past) and to move in close and look for detail... the old master paintings did this half a millennium ago, but some photographers seem to spend all their time trying to convince everyone that low-res is adequate.
-
What you say is correct, and I appreciate that Merklinger's examples refereed to film, but what does Merklinger say that you think is incorrect?
Given the topic of hyperfocal distance, I assumed we are talking about this paper (http://www.trenholm.org/hmmerk/SHBG02.pdf), where he say"s:
"So, the bottom line runs something like this. In order to ensure that distant objects are imaged sharply, we
must focus at the distance to the farthest object".
For objects at infinity that would mean one has to focus at infinity. That IMHO doesn't hold for digital sensors where one can focus closer (hyperfocal distance with a sensel pitch related COC). That will also give better foreground resolution than infinity focus will.
Cheers,
Bart
-
Some people buy big cameras to make big prints (not just for weight training), so if my sensor is N times bigger than 24 * 36mm, I want to be able to make prints 3N times bigger than you could with a 24Mpx 24 * 36mm sensor with an Anti-Aliasing filter.
I want people to be draw in to my pictures (and not just ignore them and walk past) and to move in close and look for detail... the old master paintings did this half a millennium ago, but some photographers seem to spend all their time trying to convince everyone that low-res is adequate.
Hi Dick,
I fully agree, there is no substitute for real resolution, and it can be gotten by reducing the need for magnification, IOW plenty of high quality pixels.
As for the old master painters though, they were very good at suggesting detail where there is none... Try looking at some of the old portaits how they suggested the intricate fabric of lace by coarse dabs of paint. Here they also used the 3D texture of paint itself to add to the suggestion. Same with distant detail, sometimes just well applied blobs of paint.
Cheers,
Bart
-
Hi Dick,
I fully agree, there is no substitute for real resolution, and it can be gotten by reducing the need for magnification, IOW plenty of high quality pixels.
Bart
Thanks, Bart, I am glad we are in agreement...
"Magnification" is image size divided by subject size... and it is still important, especially as the lens (rather than pixel count) is often the limiting factor, but I generally think in terms of "original camera pixels per print inch".
-
Thanks, Bart, I am glad we are in agreement...
"Magnification" is image size divided by subject size... and it is still important, especially as the lens (rather than pixel count) is often the limiting factor, but I generally think in terms of "original camera pixels per print inch".
Yes, I meant to say output magnification.
Cheers,
Bart
-
Is this toothwalker program available for a pocket PC?
-
Many responses BobFisher wrote in response to my suggestion about live view as a solution to this problem:
"How long does all that roaming around at 10x magnification take? Focus here, press this button, shift around over there, re-adjust, reset, work that setting. Might be OK for a landscape or other static scene (e.g., architecture) where no one is going to get impatient but if someone were farting around with the camera, futzing with this and that for more than about 5 seconds and I were in the group, I'd say screw it and walk away. Even with architecture, if I'm at a client location they want me in and out as quickly as possible. Wasting their time by screwing around with the camera isn't going to make them overly happy.
Dick, you're right. It would."
Since that response ridiculing my solution I have followed the discussion about charts, calculators and circles of confusion. All of these depend on theory and calculation rather than direct observation. All of them rely on the autofocus system of the camera and/or markings on the lens barrel, things that are not quite reliable or predictable. Let's think again about live view coupled with exposure simulation, manual focus at 5x or 10 x nearly anywhere in the image, and the use of stop-down depth of field preview. I submit, once again that this is the most practical solution for dSLR shooters. With this facility, I can examine the critical focus in the near, middle and far field, apply dof preview to confirm in Live View that focus is adequate. No amount of calculation, with the attendant assumptions, is going to do as well as direct observation. With a little practice one can accomplish the live view analysis in 30 seconds or so. Is this too much time for landscape photography? Is this too much time to set for a complicated group photo? I don't think so.
-
How long does all that roaming around at 10x magnification take? Focus here, press this button, shift around over there, re-adjust, reset, work that setting. Might be OK for a landscape or other static scene (e.g., architecture) where no one is going to get impatient but if someone were farting around with the camera, futzing with this and that for more than about 5 seconds and I were in the group, I'd say screw it and walk away.
For group photography I would set the camera up in advance, use something to indicate where the plain of sharpest focus is and then position the group accordingly... with a view camera, they would not need to be very close together.
-
How long does all that roaming around at 10x magnification take? Focus here, press this button, shift around over there, re-adjust, reset, work that setting. Might be OK for a landscape or other static scene (e.g., architecture) where no one is going to get impatient but if someone were farting around with the camera, futzing with this and that for more than about 5 seconds and I were in the group, I'd say screw it and walk away. Even with architecture, if I'm at a client location they want me in and out as quickly as possible. Wasting their time by screwing around with the camera isn't going to make them overly happy.
This technique can be done in less than 20 seconds, I used this technique and similar ones with my carl zeiss and nikkor PCE lenses.
I think people underestimate these high MP live view DSLR's, they are producing startling image quality, with great focus precision all in a very attractive package that handles v well in the field.
I purchased a P45+ back recently and used it with a mamiya, while the image quality is also superb, the Nikon D3x is just better in every other aspect and not far behind in image quality terms, all this and both canon and nikon are due to release the next generation cameras.
I wonder how long medium format will survive as these prices?