Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: ChristianRandwijk on December 02, 2011, 02:04:14 pm
-
Hey everyone, my first post here in this forum. I am very fond of architecture and landscape photography. And the coming year might even see me getting a couple of assignments that pay although I have an altogether different career as my dayjob. I have been looking long and hard at the beautiful ALPA cameras, and fondlede them a bit at a local store. This would be my first foray into digital MF, and I have some concerns about depth of field and diffraction. How far down do you ALPA users feel comfortable stopping down, and does this yield enough depth of field for landscape photography? I have been looking hard at the Cambo RS as well, especially since they make lensmounts, for some lenses, that tilt/swing. Apparently tilt isn't possible with shorter lenses than 80mm in the ALPA system, but I might be wrong.
-
Hi,
With good lenses stopping down past f/8 will loose some resolution. The better the lens the less can you stop down. On the other hand, diffraction is benign to sharpening.
If you need to stop down, f/16 is quite OK. You are loosing significant sharpness. Past that you start to loose a lot.
This page shows the effects of diffraction and defocus. Left column correctly focused, the other columns are defocused 3, 6 and 9 cm at 3 meters with a 100/2.8 macro lens.
The test was done with an APS-C DSLR, but the same laws of physics apply to any lens and to any sensor format.
Best regards
Erik
Hey everyone, my first post here in this forum. I am very fond of architecture and landscape photography. And the coming year might even see me getting a couple of assignments that pay although I have an altogether different career as my dayjob. I have been looking long and hard at the beautiful ALPA cameras, and fondlede them a bit at a local store. This would be my first foray into digital MF, and I have some concerns about depth of field and diffraction. How far down do you ALPA users feel comfortable stopping down, and does this yield enough depth of field for landscape photography? I have been looking hard at the Cambo RS as well, especially since they make lensmounts, for some lenses, that tilt/swing. Apparently tilt isn't possible with shorter lenses than 80mm in the ALPA system, but I might be wrong.
-
The effects of diffraction and the lack of DoF is overemphasized in MFD photography. Most of this comes from viewing at 100% which matches no real-world viewing distance of an image. I constantly read you cannot shoot at f/16 and so I made an image at f/22 and printed it on 36" roll paper. It is in my living room and it is a beautiful image. Yes, you can compare two images at f/11 and f/16 and see the difference in diffraction at 100%, but are your final viewers going to be looking at comparison shoots on a monitor at 100%? I don't know many members of the public who are pixel peepers and judge images solely on technical considerations.
-
Hi,
Quite true, but resolution is one of the primary reason for going to MFDB and definitively the reason for buying high end MF lenses like HR Digitars. Why spend a lot of money on optical excellence if it's thrown away by stopping down?!
The other advantages with MF are also available with lesser lenses and backs.
Best regards
Erik
The effects of diffraction and the lack of DoF is overemphasized in MFD photography. Most of this comes from viewing at 100% which matches no real-world viewing distance of an image. I constantly read you cannot shoot at f/16 and so I made an image at f/22 and printed it on 36" roll paper. It is in my living room and it is a beautiful image. Yes, you can compare two images at f/11 and f/16 and see the difference in diffraction at 100%, but are your final viewers going to be looking at comparison shoots on a monitor at 100%? I don't know many members of the public who are pixel peepers and judge images solely on technical considerations.
-
Hi,
Quite true, but resolution is one of the primary reason for going to MFDB and definitively the reason for buying high end MF lenses like HR Digitars. Why spend a lot of money on optical excellence if it's thrown away by stopping down?!
It is a matter of balance. What is the point of minimizing diffraction when you don't have enough DoF for the object? A photograph is more than a technical study in resolving power. Also, the great optics will continue to work better at small apertures than bad optics and so you are really not throwing anything away. And MF sensors sizes and pixel resolutions are really forgiving--just because you see pixel level changes, does not mean it is significant for the image as a whole.
Personally, I went to MFD for the sensor size, not the pixel density. When I put prints from my 22MP Phase images next to my 40MP Pentax images, the extra pixels of the Pentax is really not adding a great deal. The magic of MFD goes beyond the number of pixels. And when you think diffraction at f/16 is not a problem in the 22MP Phase, just because you can see it in the 40MP Pentax at 100%, it does not make any difference when it gets printed--the human eye can only resolve so much. This is really a relative problem related to format rather than an absolute one measured in pixels.
Now, I am like every one that shoots MFD, I love viewing the files at 100% to see the fine details--just look at the hairs on those flies! But in practical terms, the detail is not going to be seen under normal viewing conditions. That does not mean I don't think over sampling is meaningless. Things are smoother. Details have a nice crispness to them. There are real benefits. But this fixation of diffraction and a compulsion to squeeze out every piece of resolution at the focus planes so it can be viewed at 100% on my monitor at the expense of the content of the photograph is something I don't understand.
-
If you wanted the sexiness of an Alpa but with the functionality of the RS tilt-swing for wider lenses I personally think (highly biased - see signature) the Cambo RS AE (http://www.captureintegration.com/tech-cameras/wide-rs-wide-ds/) is very sexy while still being very functional.
For anyone on the forum to provide you guidance on diffraction you have to tell us what digital back you have as the resolution and pixel size of the back are a huge factor in which aperture will be noticeably soft but recoverable with proper sharpening and which aperture will result in major loss of sharpness.
Also it would be helpful to know what focal lengths you find you use most often with your current system, as focal length also plays a big role here. If you're an ultra-wide lens kinda guy then DOF will not be a challenge even with the highest resolution backs. If you like semi-wides the story will be a bit different. Compositional tendencies also matter a LOT (do you compose more sweeping landscapes lacking foreground or do you like to often feature foreground elements). Links to your current body of work are a great way to start to answer these questions.
Disclaimer: my company (Capture Integration) has opted to sell Cambo (and Arca) but not Alpa. So we must be considered biased.
Doug Peterson (e-mail Me) ([email protected])
__________________
Head of Technical Services, Capture Integration
Phase One Partner of the Year
Leaf, Leica, Cambo, Arca Swiss, Canon, Apple, Profoto, Broncolor, Eizo & More
National: 877.217.9870 | Cell: 740.707.2183
Newsletter (http://"http://www.captureintegration.com/our-company/newsletters/") | RSS Feed (http://"http://www.captureintegration.com/2008/08/11/rss-feeds/")
Buy Capture One 6 at 10% off (http://"http://www.captureintegration.com/phase-one/buy-capture-one/")
-
Thanks for the good replies so far. Well, my current equipment is a 5D2 with an assortment of nice lenses. I had been looking at getting the 24mm TS-E for the Canon. But the expense of eventually getting the three tilt-shift lenses for the Canon put me close to MF territory, as far as a body and lens goes (depending on the make ofcourse). I could start off renting a Digital back. That got me thinking. Also, I've played around a bit with an old 4x5 camera, and really like the slow, contemplative workflow (although I found focusing somewhat of a challenge, but then, challenges aren't a bad thing). The cost of buying, developing and scanning 4x5 slides here in Denmark is ridiculously high, so in the long run a digital investment makes more sense.
As for shooting style, I'm not really an ultrawide person, I like 28mm (on 5D) better than 24mm, but a hypothetical 26mm would probably be my perfect wide lens. I really like the look of dramatic landscapes with foreground interest and a nice sweep towards the horizon; I am a very big fan of Joe Cornish.
The reason for looking at ALPA first is, well, sexiness, but also, I don't think anyone in Denmark is stocking the Cambo, so I have had no possibility of "seeing" it, with my hands. I don't think I'm a brand snob, so if Cambo would be the most sensible solution, price-wise, then I'd go with that. But, I think, no possibility of trying it out in Denmark, nor the Arca Swiss or Sinar technical cameras.
As for diffraction, DOF a.s.o., I'm not so worried about how it looks at 100% on my computer, prints are the thing. But, MF digital is a huge investment, so I just want to make sure I use my money wisely. I think the newer digital lenses are optimised for shooting at around f/8 (I might be mistaken), which wouldn't yield that much DOF on a 35mm or a 43/47mm lens. Hence the wish for being able to use tilt to increase DOF.
-
Hi!
This is from a comparison done with P45 back on a Hasselblad in the "Great 2006 MFDB shootout" by Michael Reichmann, Bill Atkinson and Charlie Cramer.
Left one is f/8 and right one is f/16, you may need to click a few times to see full size image.
Updated: I made prints from these two images in large size (I don't recall the size but probably around 30x40"). The difference between f/8 and f/22 was definitively obvious at 1-2 meter viewing distance. A photograph of a one dollar bill taken with my Sony Alpha 900 at f/8 is essentially on par with the f/22 image on the H1/P45 combo. So the difference really matters in print. But I used same sharpening for both f/8 and f/22.
Best regards
Erik
Thanks for the good replies so far. Well, my current equipment is a 5D2 with an assortment of nice lenses. I had been looking at getting the 24mm TS-E for the Canon. But the expense of eventually getting the three tilt-shift lenses for the Canon put me close to MF territory, as far as a body and lens goes (depending on the make ofcourse). I could start off renting a Digital back. That got me thinking. Also, I've played around a bit with an old 4x5 camera, and really like the slow, contemplative workflow (although I found focusing somewhat of a challenge, but then, challenges aren't a bad thing). The cost of buying, developing and scanning 4x5 slides here in Denmark is ridiculously high, so in the long run a digital investment makes more sense.
As for shooting style, I'm not really an ultrawide person, I like 28mm (on 5D) better than 24mm, but a hypothetical 26mm would probably be my perfect wide lens. I really like the look of dramatic landscapes with foreground interest and a nice sweep towards the horizon; I am a very big fan of Joe Cornish.
The reason for looking at ALPA first is, well, sexiness, but also, I don't think anyone in Denmark is stocking the Cambo, so I have had no possibility of "seeing" it, with my hands. I don't think I'm a brand snob, so if Cambo would be the most sensible solution, price-wise, then I'd go with that. But, I think, no possibility of trying it out in Denmark, nor the Arca Swiss or Sinar technical cameras.
As for diffraction, DOF a.s.o., I'm not so worried about how it looks at 100% on my computer, prints are the thing. But, MF digital is a huge investment, so I just want to make sure I use my money wisely. I think the newer digital lenses are optimised for shooting at around f/8 (I might be mistaken), which wouldn't yield that much DOF on a 35mm or a 43/47mm lens. Hence the wish for being able to use tilt to increase DOF.
-
Christian,
If you find a good local dealer the option of renting can be surprisingly viable. I rented a back from my dealer at great rates because I wanted the back over the weekend, which is when they usually sit idle. Then as long as no one was in the que for the back I could keep it for extended periods.
My experience with DoF is that both sides of the argument are valid. At 100% you will see a difference on the screen between f/8 and f/16. In a print, even a big print, you will struggle to see the difference, and anyone else will not notice unless they are prompted and trained to look for it. My rule of thumb when in the field is to not worry about diffraction on a ~54x40 sensor up to f/16. If I need more DoF I will either focus blend or make a "what's most important" focus choice. That may vary if I know ahead of time what the image will be used for.
I believe people tend to underestimate the advantage of a larger sensor area when printing. When we used film no one argued about the benefits of MF over 35mm when printing larger, even though the film was exactly the same emulsion. Point being when you print a MF file diffraction issues are not magnified as much on the print, which gives you more leeway than the 100% screen view might make you think.
Dave
-
But, MF digital is a huge investment, so I just want to make sure I use my money wisely. I think the newer digital lenses are optimised for shooting at around f/8 (I might be mistaken), which wouldn't yield that much DOF on a 35mm or a 43/47mm lens. Hence the wish for being able to use tilt to increase DOF.
I would say the new digital lenses are more optimized for resolving power rather than contrast. Lenses, film or digital, historically have always worked better at f/8 if you are using a simple technical scale. Digital lenses may also show some more improvement wide open, especially view camera lenses like the ones used on the Alpa. As far as small apertures, nothing has really changed. As far as my shooting experience goes, the added DoF field easily trumps any increase in diffraction. But this is also a digital world and you can use focus-stacking software like Helicon focus to shoot multiply images of a scene at different distances and combine them for a sharp image. The technology is not without its downsides as artifacts can be introduced--as you focus, you change image size and edge artifacts can be seen, not always and some are easily fixed in Photoshop, but that is also more work for you.
When I was researching MFD, I kept reading how difficult is was and such. Now, I have used many formats over my career from 35mm to 8x10, so when I finally got my first MFD, a P25+ on a Linhof M679, I really did not find it hard at all. Except for remembering to wake up the back, some bugs with tethering, and shooting LCC to correct color casts introduced by the optics, there was nothing really unique about the shooting process. I think if you are a skilled photographer, you will be fine with the systems. Of course when I started with these larger files, suddenly I also had to address storage and computer power. My Pentax is as easy to use as any DSLR.
As a business decision, that is something only you can answer. There will be an increase in quality that you will see, it may not be significant for your clients. Could shooting MFD be a selling point to get more clients and move your career along, possibly. You could also start by renting the equipment for a few shoots to see how it works and how your clients react--you bill the rental costs to them as well.
-
Double posting. What Dave said.
-
The reason for looking at ALPA first is, well, sexiness, but also, I don't think anyone in Denmark is stocking the Cambo, so I have had no possibility of "seeing" it, with my hands. I don't think I'm a brand snob, so if Cambo would be the most sensible solution, price-wise, then I'd go with that. But, I think, no possibility of trying it out in Denmark, nor the Arca Swiss or Sinar technical cameras.
If seeing it is the only obstacle I'm sure many dealers (I can only directly speak for us) would be happy to do a video chat conference with you with the gear. And if you want to get your hands on one a paid rental which is counted towards your purchase (if you do purchase) is a great option.
-
As an ALPA user and an architectural/industrial shooter I would suggest to you that the whole DOF discussion online has been hijacked by "measurers" (I call them something else, but I can't use that word here). Technically, diffraction becomes more of an issue as pixels get smaller. Hence, in theory, the all singing, all dancing IQ180 and Aptus12 backs (I own both of these backs), with a pixel pitch of 5.2 microns are the worst performers in this regard. This is correct in both theory and in fact. Yet somehow, they are producing the best quality files I've ever shot.
Modern digital lenses are optimised for the larger apertures. As an example, my 23HRS is at its best between f5.6-f8. My 35XL is best around f8. However, these lenses are so ridiculously sharp to start with, that it takes the most ardent pixel peeper to spot any observable image degradation even at f16. Keep in mind that at f16 I have more DOF than I know what to do with and prints look pin sharp even at sizes over 1.5m. If someone is evaluating my work based on absolute resolution, then I've clearly not done my job, which is to create engaging memorable images. It's about the images, not the sharpness of that line on the edge of the frame.
I think it is important that you get your head around the subject of DOF and diffraction, but in the final washup, it's a minor issue when you are dealing with this level of gear.
What IS important, is that cameras like the Alpa are rigid and precise as depth of focus (as opposed to depth of field) is miniscule with wide lenses. This is why Alpa go to the trouble of shimming mounting adapters. This simple step contributes more to image quality than any amount of worrying about DOF.
My Alpa STC and the lenses from Rodenstock and Schneider that mount on it are purely and simply the most precise, finest quality photographic devices I have ever had the pleasure of working with. The sheer simplicity of the camera makes it a joy to work with.
Cheers
-
The good news, sort of, is that the trade-offs between DOF (judged at a certain print size and viewing distance, so it gets a bit harder when your aim is high res. images for "printing large and viewing close") do not depend much if at all on the camera or format. So if the combination of detail/resolution and FOV and subject distances and DOF you want is optically possible, then the gear you use can achieve that so long as it can give the FOV and resolution you need.
-
DoF with medium format digital is certainly different to what you may become used to when shooting with either film or 35mm digital. However, I agree with the other posts here in that it's not as big of an issue in reality as some people would have you believe. In particular, the current trend amongst folks shooting with technical cameras is to believe that the sky is falling if they don't have tilt and scheimpflug ... don't believe a word of it! I don't see the whole fraternity of MF DSLR shooters dumping their gear because of this and, as Bryan Siebel notes, neither he nor his clients have any issues with the quality of his work due to the perceived DoF problem.
As mentioned, the secret is understanding what's important in your images and ensuring that's where you hold critical focus. I find that there's a tremondous difference between pixel peeping sharpness throughout an image and what's usable in print. When I do want to achieve maximum DoF I find that following basic rules about finding the critical focus point & f-stop for your lens/sensor combination goes a long way to making shooting easier. You might find the following useful as a reference, particularly as they apply to the Alpa or any other technical camera:
http://optechsdigital.com/Alpa_and_Hyperfocal.html
http://blog.phaseone.com/2011/03/31/achieve-sharp-images-with-wide-angle-lenses
When all else fails, i'll certainly stop down to f/16 or so or I'll shoot a focus bracket stack at optimal aperture of f/8 or f/11.3 depending upon the lens and combine them either using Helicon Focus or Photoshop. I can do that MUCH faster than I can achieve selecting critical DoF with tilt/swing using even my IQ back and "live view". In most situations a stack of two, three or four images can handle toes to infinity with any wide angles 47mm and below) or even my 90/150mm depending upon the scene.
This is four images stacked with a STC 47 XL APO Digitar on P40+:
http://www.grahamwelland.com/DVSaltCrystals/index.htm
Or a two image stack that tilts wouldn't help with STC/IQ160/35 XL APO Digitar (as-is default C1 Pro sharpening only btw):
http://www.grahamwelland.com/Japanese-Maple-Alpa/index.htm
Now I'm not saying that tilts aren't that important overall (heck I'm testing the Alpa T/S adapter that i have on loan at the moment myself plus I do shoot with a Hartblei 45 super-rotator on my DF too), but even with an IQ back with live view it's not easy to do compared to T/S lenses on a 35mm DSLR with EXCELLENT live view (I used to use Nikon 24/45/85 PC-Es with my D3x), and particularly compared to shooting with a 4x5 on a decent ground glass & loupe. Anyone who can do it using a ground glass with an Alpa, Cambo, Arca, Linhof technical vs LF etc has my respect and admiration because I could hardly even focus mine with a 4x loupe, least of all consider trying to do tilts.
Note to Alpa: you really do need to have a wide angle T/S offering soon because I know from dealers and folks that have swapped systems that it's hurting ...
-
My experience with DoF is that both sides of the argument are valid. At 100% you will see a difference on the screen between f/8 and f/16. In a print, even a big print, you will struggle to see the difference, and anyone else will not notice unless they are prompted and trained to look for it. My rule of thumb when in the field is to not worry about diffraction on a ~54x40 sensor up to f/16. If I need more DoF I will either focus blend or make a "what's most important" focus choice. That may vary if I know ahead of time what the image will be used for.
I believe people tend to underestimate the advantage of a larger sensor area when printing. When we used film no one argued about the benefits of MF over 35mm when printing larger, even though the film was exactly the same emulsion. Point being when you print a MF file diffraction issues are not magnified as much on the print, which gives you more leeway than the 100% screen view might make you think.
Dave
+1 for what Dave articulately said!
-
So well said Bryan,
The ultimate precision is required for DBs like the IQ 180 and the Leaf 12, especially when it comes to "depth of focus". Slowly but surely it is recognized that shimming the back makes a difference, and it does. Working with such high-resolution (and small pixels) devices and high-resolution lenses (HRs) is not forgiving.
Thierry
As an ALPA user and an architectural/industrial shooter I would suggest to you that the whole DOF discussion online has been hijacked by "measurers" ... ... Keep in mind that at f16 I have more DOF than I know what to do with and prints look pin sharp even at sizes over 1.5m. If someone is evaluating my work based on absolute resolution, then I've clearly not done my job, which is to create engaging memorable images. It's about the images, not the sharpness of that line on the edge of the frame.
I think it is important that you get your head around the subject of DOF and diffraction, but in the final washup, it's a minor issue when you are dealing with this level of gear.
What IS important, is that cameras like the Alpa are rigid and precise as depth of focus (as opposed to depth of field) is miniscule with wide lenses. This is why Alpa go to the trouble of shimming mounting adapters. This simple step contributes more to image quality than any amount of worrying about DOF.
My Alpa STC and the lenses from Rodenstock and Schneider that mount on it are purely and simply the most precise, finest quality photographic devices I have ever had the pleasure of working with. The sheer simplicity of the camera makes it a joy to work with.
-
DoF with medium format digital is certainly different to what you may become used to when shooting with either film or 35mm digital. However, I agree with the other posts here in that it's not as big of an issue in reality as some people would have you believe. In particular, the current trend amongst folks shooting with technical cameras is to believe that the sky is falling if they don't have tilt and scheimpflug ... don't believe a word of it! I don't see the whole fraternity of MF DSLR shooters dumping their gear because of this and, as Bryan Siebel notes, neither he nor his clients have any issues with the quality of his work due to the perceived DoF problem.
I can only agree with this.
As mentioned, the secret is understanding what's important in your images and ensuring that's where you hold critical focus. I find that there's a tremondous difference between pixel peeping sharpness throughout an image and what's usable in print. When I do want to achieve maximum DoF I find that following basic rules about finding the critical focus point & f-stop for your lens/sensor combination goes a long way to making shooting easier. You might find the following useful as a reference, particularly as they apply to the Alpa or any other technical camera:
http://optechsdigital.com/Alpa_and_Hyperfocal.html
http://blog.phaseone.com/2011/03/31/achieve-sharp-images-with-wide-angle-lenses
Yes, that's of extreme importance, to understand and to use the hyperfocal of the lens. It is such simple, self-explaining and fast to use, while absolutely precise and reliable, that not using hyperfocal focusing is a mistake.
When all else fails, i'll certainly stop down to f/16 or so or I'll shoot a focus bracket stack at optimal aperture of f/8 or f/11.3 depending upon the lens and combine them either using Helicon Focus or Photoshop. I can do that MUCH faster than I can achieve selecting critical DoF with tilt/swing using even my IQ back and "live view". In most situations a stack of two, three or four images can handle toes to infinity with any wide angles 47mm and below) or even my 90/150mm depending upon the scene.
This is four images stacked with a STC 47 XL APO Digitar on P40+:
http://www.grahamwelland.com/DVSaltCrystals/index.htm
Or a two image stack that tilts wouldn't help with STC/IQ160/35 XL APO Digitar (as-is default C1 Pro sharpening only btw):
http://www.grahamwelland.com/Japanese-Maple-Alpa/index.htm
Wonderful image samples showing the possibilities of focus stacking and the "Helicon Focus", especially the maple tree where tilt and/or swing won't bring anything.
Note to Alpa: you really do need to have a wide angle T/S offering soon because I know from dealers and folks that have swapped systems that it's hurting ...
Well heard and understood, see my announcement about this new T/S possibilities with short focal lenses on any Alpa 12 camera system, here:
New Alpa Tilt Capacity with Wide Lenses (http://www.luminous-landscape.com/forum/index.php?topic=59833.0)
Thierry
-
+1 for what Dave articulately said!
+1
Thierry
-
And as we are talking about the overemphasis on certain technical matters, Apla does have a long history of overemphasizing precision in their marketing--hey, it helps sell cameras and more power to them. Personally, their marketing turns me off. Alpas are fine cameras and I would certainly recommend them. But the physics of photography is really not that hard to figure out. Shimming has really become overemphasized.
And one small note, depth of focus is a product of the f-number, not the focal length. If you have to shim your wides, you need to shim your normals and telephotos if you are using them at the same apertures. If shimming is required at all. And this always confused me, since you shim the back, what happens when the tolerances in the lens mount requires different shims? And how does all of this work with temperature changes? Personally, Alpas are great cameras and I would not worry about the shim thing.
-
Christian,
I copy the following from Joe Cornish's website. Nowhere does he mention resolving power,diffraction
or,even, circle of confusion :)
Personally,if I were you, my first step would be to buy the 24 and 45 tilt shifts for your 5d Mkll.
When used in a 'slow and contemplative' style, using left/right or top/bottom stitching,and
paying attention to post processing the files are extremely capable.
"I am now actively working to that end in four digital formats. They include a digital compact (Panasonic Lumix LX-3); so-called 4/3rds (Olympus E3); 'FX' or full frame 35mm digital (Nikon D-700); and finally, medium format digital (Phase One P-45+). The resolution of the first three formats is really very similar, around 10 or 12 megapixels, while medium format is in a different league of 39mp. The Phase One is usually deployed on the amazing Linhof Techno field camera, helping me preserve my link with large format discipline. Why so many formats? Because the variety is stimulating, and each camera has its own particular strengths (and weaknesses). Who knows, I may eventually concentrate on medium format exclusively; it is the natural successor to LF film. Yet as I write this I am enjoying the challenges that variety offers, and still feel in the early days of my photographic 're-learning curve'.
-
And one small note, depth of focus is a product of the f-number, not the focal length. If you have to shim your wides, you need to shim your normals and telephotos if you are using them at the same apertures. If shimming is required at all. And this always confused me, since you shim the back, what happens when the tolerances in the lens mount requires different shims?
Well, the fact of the matter is that you DO need to have your lenses in exact calibration on their mounts. If they are off then shimming the back alone won't be sufficient. I had to have one of my Alpa mount lenses calibrated by my dealer because it was out of spec from the other three that all had perfect registration with my shimmed back.
Some vendors claim that shimming isn't' necessary because all lenses are calibrated at the factory, as are the back mounts. Well maybe they have better QC than anyone else because many of us know from bitter experience that even Leica can't manage that! Arca do have a calibration scheme that can accommodate both variance in the sensor position/back flange and also lens tolerances since each combination has it's own offset when setting focus - you just need to keep track of them although that doesn't seem so hard if you only have a few lenses which let's face it most tech shooters typically do.
-
Well, the fact of the matter is that you DO need to have your lenses in exact calibration on their mounts.
What do you mean by "exact"? Even Alpa has manufacturing tolerances and so perfection is impossible. And how do you focus? Live view? So if the image is sharp on live view, what difference is a bit of shimming going to make. Are you using a ground glass? Then the only thing that matters is the difference between the GG and sensor plane. Are you using the focus scale and small apertures, then the discussion of accuracy vs. precision is valid. And absolute precision is impossible and not required for any imaging device that uses a CoC, especially with objects with depth--if you photograph a landscape at f/11, is it going to make a difference if the focus is at 60ft or 61ft?
Cameras are precision instruments, but to say you need perfection is a mistake, especially since it cannot be achieved nor is it required. Do you shim your Sinar? (I believe you use a Hy/6, if I got the name right) Have you had focusing issues?--I believe you cannot shim that camera. I manual focus my Pentax 645D with manual-focus lenses and that has a viewing system that has to be more precise than a simple design such as an Alpa and I get sharp images all the time. I have no problem focusing my Phase back on a Linhof 679c with a sliding back and GG.
I am curious what Alpa thinks the CoC of the IQ180 is? We can then calculated the depth of focus and compare it to the shims it offers.
Now, I think Alpa cameras are great. I am not trying to knock the product--they are well worth buying and using. I am simply questioning their claim about shimming and its practicality--it sort of falls into recent discussion over diffraction at 100%. Not that MFD shooters suffer from OCD or anything...
-
Different Graham - I shoot with an IQ160 & P25+ with Alpa STC & Phase One DF.
Remember that focusing and shooting with a technical camera is completely different to using a DSLR like the 645D. There is no direct view in practice.
In answer to your question, you need to have a fixed reference point on your lens if you want to use the marked focus distances on the helicoid. That reference point is as close to infinity as is practical. I use the HPF rings which do provide very granular distances that you can use along with a distometer close up or a rangefinder at further distances. This means that if something measures 5ft away then I can dial in 5ft on the focus ring and I know that it will focus there and not at 4.9ft or 5.1ft - at these distances the accuracy is critical. Now when you get to 60ft vs 61ft, sure its not so much of a big deal so long as DoF covers it although if that's your primary focus subject and you want it spot on then you want to know that when you measure 60ft and dial that in, it really is tack sharp at that distance.
Focusing with a ground glass is impractical IMHO with digital backs vs film but it is an option - I personally find it almost impossible with a loupe on a 6x6 GG. I just don't bother with that.
Live view - hmm, well that's a work in progress in my view with the IQ. Yes, when it is clear enough and you've got everything set up correctly then yes you can absolutely dial in the critical focus on screen and all of the shimming & mount calibration is irrelevant. However, we're not there yet ... at least not outdoors in varied lighting conditions.
What I can tell you is that when everything is dialed in correctly and shimmed, when I set focus to infinity I get sharp at infinity. From there every other focus mark is correct on the ring. Now personally I do a fair amount of focus stacks that include infinity and so I want that sharp as one of my reference images. I'll then zone in from there for an image stack.
You could certainly argue that if you calibrate your own hyper-focal settings manually using the procedure I linked to in an earlier post, whether the marked infinity really is accurate or not for each lens/aperture probably doesn't matter so much either. However, that's no different than knowing your lens front or back focus and applying your own fudge factor every time you shoot (or more likely forgetting or not getting it right and getting softer shots than you expect).
-
And as we are talking about the overemphasis on certain technical matters, Apla does have a long history of overemphasizing precision in their marketing--hey, it helps sell cameras and more power to them. Personally, their marketing turns me off. Alpas are fine cameras and I would certainly recommend them. But the physics of photography is really not that hard to figure out. Shimming has really become overemphasized.
And one small note, depth of focus is a product of the f-number, not the focal length. If you have to shim your wides, you need to shim your normals and telephotos if you are using them at the same apertures. If shimming is required at all. And this always confused me, since you shim the back, what happens when the tolerances in the lens mount requires different shims? And how does all of this work with temperature changes? Personally, Alpas are great cameras and I would not worry about the shim thing.
With all due respect, you are wrong when saying that shimming is overemphasized and not that important, let alone that precision of a system isn't either. I invite you to come and visit us in Zürich, and we will show you what it means in practical terms and that it is not a question of marketing.
Concerning your question with the lenses: it is expected that each lens is absolutely well adjusted to infinity, which can be done as well.
Best regards
Thierry
-
One would expect that this calculation has been made, and yes it has been. But it needs only to shoot a couple of images at "infinity", taking away a shim or adding one to see the difference.
On a side note: nobody claims that Alpa is the perfection, at least not me nor Graham or anybody at Alpa, but what we try to say is that with the current high-res backs and their pixel size, a camera system has to be as precise as possible, with the minimum possible tolerances. A system is only as good as the weakest part in the whole chain is: better to have all elements of this chain from lens to DB as precise as possible. That is what Alpa is trying to achieve, by different means and techniques in the manufacturing of the cameras and their accessories.
Best regards
Thierry
I am curious what Alpa thinks the CoC of the IQ180 is? We can then calculated the depth of focus and compare it to the shims it offers.
-
Hi,
Theguywiththe645 has a good point on thermal expansion. On a 5 cm long body of Aluminium it would be 23 micron for a 20 degree change. The focal length of the lens may change to. That is part of the reason many lenses can focus past infinity.
Best regards
Erik
With all due respect, you are wrong when saying that shimming is overemphasized and not that important, let alone that precision of a system isn't either. I invite you to come and visit us in Zürich, and we will show you what it means in practical terms and that it is not a question of marketing.
Concerning your question with the lenses: it is expected that each lens is absolutely well adjusted to infinity, which can be done as well.
Best regards
Thierry
-
All I can say is you guys with Alpa's are lucky - in two ways - 1st because its a great camera, and 2nd because mostly you'll never work with macro stuff. That's the area where I experience the biggest challenge with DOF and diffraction effects. It's not my experience that the losses don't show in prints - I see them in even 20x24 prints with subject matter that has fine detail. But there are software workarounds that help recover this detail ie richardson Lucy, so it's not untenable.
-
I invite you to come and visit us in Zürich, and we will show you what it means in practical terms and that it is not a question of marketing.
Best regards
Thierry
Thierry, when I am lucky enough to visit, I would be delighted to take you up on your offer.
Graham, sorry for getting you and your camera confused. I have used technical camera, but since it was a film one, I did not want to mention it and open up a can of worms.
I guess what I may be reacting to is this monster that MFD is somehow extremely difficult, unless you set your camera on a steel pier with a shutter speed of 1/250 at f/11 and at the base ISO. You just have to wait for the sun to give enough light to take the image. I have not found for photographers that have mastered the photographic process, both professional and amateur, that it is really that difficult a leap. Perhaps LCCs and the effects of lens cast may be "hardest" thing about the process. But shooting MFD is no superhuman task, which I find it seems to be portrayed.
And there have always been different flavors of photographers. Some are very detail oriented and others are looser in their process and work. Both ends of the spectrum produce fine images--we can disagree on aesthetics, but we are in the realm for personal taste at that point. MFD is fine for all photographers and I would encourage an skilled photographer to pursue MFD if the interest is there and trust they will have the skills to get what they need. I have not found shooting MFD any different from any format I have shot--from 16mm to 8x10. And I have been printing much of my work all the way up to 4x12 feet.
There was a thread recently about using an Alpa for handheld portraiture in the field. Many folks really did not like the idea of that. Having done similar work, I thought it was quite a valid way of shooting. (I am sure I could do that with an Alpa off-the-shelf with no shimming ;) ) Because of cost, MFD has gone where the money is, mostly commercial work which has a very specific approach to photography with a definite technical bent--I know I am painting with a broad brush. I guess I am an advocate of seeing MFD hit areas of photography that have been underrepresented. I think want may put some folks off is this perception that it is somehow different and really hard.
I will get off my soapbox.
Peace...
-
No worries - hey, I actually agree with you about how easy it is in reality to shoot MF with technical cameras actually. Personally I almost always get better results when I use my Alpa vs my DF if only because it's a more considered shooting experience and not technically difficult, other than of course remembering to do everything in the right order. Ditto LCCs - simple stuff if you have a process that you follow. If I can do it, it must be easy. ::)
As regards handheld shooting & zone focus - yup, simple if you've got enough light. Shimming will still matter if you want to shoot at infinity though - but yes you have a very valid point. ;)
-
I think shooting with a tech camera can be as simple or as difficult as you want it to be.
It's one of the things I like about it!
Really. No meter, no ai/oneshot/servo/manual focus mumbo, and barely a viewfinder (I lived for almost a year without one - still have to pick it up from my dealer). Just me and the outdoors!
Oh, and I never grab the zoom ring by mistake instead of the focus ring.
Dave
ps. If someone comes out with a zoom lens for a tech camera I will hang myself. And no the Hartblie doesn't count. :)
-
Hello All,
I have to admit, I was a little skeptical as to the importance of shimming a back. Having recently returned from visiting the folks over at ALPA, I can attest that the difference of .1 mm is clearly apparent. The ALPA system is really quite impressive. (yes, I do have some bias here being an ALPA dealer).
Having said that, I cut my teeth in photography with a 4x5 using tilts and swings for focus control. I'm very excited to see what ALPA has in the works regarding future T/S possibilities being incorporated into their wider lenses.
Denny
With all due respect, you are wrong when saying that shimming is overemphasized and not that important, let alone that precision of a system isn't either. I invite you to come and visit us in Zürich, and we will show you what it means in practical terms and that it is not a question of marketing.
Concerning your question with the lenses: it is expected that each lens is absolutely well adjusted to infinity, which can be done as well.
Best regards
Thierry
-
Hi Denny,
Welcome in the Alpa team. And thanks to confirm my statement.
Just to be clear myself as well:
I was myself as well much skeptical before seeing what shimming means, but I was well aware from my Sinar time and the experience with tousands of DBs in the market that sensor alignment was a serious issue.
However, it is most of the time difficult to see that an image is actually OOF or that the focus is slightly (or even much) at the wrong place, simply because one has no reference to compare. An image can seem to be absolutely perfectly focussed/sharp and though it isn't the best possible which can be reached.
By doing a test and by changing the position of the sensor, means the distance to the lens plane by shimming + or - by increments of mms, it clearly shows visually when comparing 2 images what e.g. 1/100 mm can change in terms of sharpness.
Best regards
Thierry
Hello All,
I have to admit, I was a little skeptical as to the importance of shimming a back. Having recently returned from visiting the folks over at ALPA, I can attest that the difference of .1 mm is clearly apparent. The ALPA system is really quite impressive. (yes, I do have some bias here being an ALPA dealer).
Having said that, I cut my teeth in photography with a 4x5 using tilts and swings for focus control. I'm very excited to see what ALPA has in the works regarding future T/S possibilities being incorporated into their wider lenses.
Denny
-
Hello again,
thank you all for providing loads of information for me to chew on. And I'm very excited about a possible future t/s system for Alpa. I am guessing a good disposition for me now would be to find a 24mm TS-E v2 to try out the movements on my 5D2, and then see what the next year or so holds for me, budgetwise. So again, thank you all for the input.
-
Ah..yes...decimal points matter.
That should have been .01 mm.
;)
...the difference of .1 mm is clearly apparent.
-
Hi Thierry,
Would yo be able to post a comparison image demonstrating the effect of a subject being 0.01 mm defocused (in the image plane)?
Not that I'm overly skeptical, but my understanding is that the "CoC" caused by defocus in the image plane is defocus divided by f-stop, so 0.01 mm of defocus at f/4 would give a circle of confusion of 2.5 micron, much smaller than the sensor pitch.
Best regards
Erik
Hi Denny,
Welcome in the Alpa team. And thanks to confirm my statement.
Just to be clear myself as well:
I was myself as well much skeptical before seeing what shimming means, but I was well aware from my Sinar time and the experience with tousands of DBs in the market that sensor alignment was a serious issue.
However, it is most of the time difficult to see that an image is actually OOF or that the focus is slightly (or even much) at the wrong place, simply because one has no reference to compare. An image can seem to be absolutely perfectly focussed/sharp and though it isn't the best possible which can be reached.
By doing a test and by changing the position of the sensor, means the distance to the lens plane by shimming + or - by increments of mms, it clearly shows visually when comparing 2 images what e.g. 1/100 mm can change in terms of sharpness.
Best regards
Thierry
-
This is from an old post of mine, from a topic that dealt with camera tolerances, it's a couple of years old but still valid IMO:
"To be honest I always thought that all the talk about 0.01 mm was to much marketing talk and I thought with a smile on the face, that the fussiness about so small tolerances had something to do with the water they drink in switzerland :-) - that was until I got a new back that had a bit different focus plane than the old, I took the adjustable Alpa V adapter and started to shim it - I don't smile anymore at the swiss, only at my own ignorance....... 0.1 mm (millimetre) change the focus a lot and yes you can just see a difference in 0.01 mm - it do not ruin the image at all, but there is a difference..... yes it's too scary"
/adam