Some interesting points. This would be even more true if the rumors were accurate about some of these DSLRs not having an AA filter.
http://www.diglloyd.com/
Cheers,
Bernard
Thanks for the link Bernard - Very interesting reading.
If Nikon do bring out the much rumoured 36mpx camera it will indeed set the cat amongst the proverbial pigeons.
I don't see that it changes anything regarding technique. Cameras with equivalent (or smaller) pixels already exist on the market and have for several years. A given absolute amount of shake (due to wind, slap, etc.) will have just as much pixel-level blur on these existing cameras.
I don't see that it changes anything regarding technique. Cameras with equivalent (or smaller) pixels already exist on the market and have for several years. A given absolute amount of shake (due to wind, slap, etc.) will have just as much pixel-level blur on these existing cameras.The pixel count and angular resolution is more important than pixel size alone: getting the same FOV in a larger format with more pixels of the same size means a longer focal length, so that the same degree of camera movement causes more image movement across the focal plane, so more "pixels-worth" of blur.
And that field curvature "problem", is it really a problem for anything else than shooting flat test charts?
Yes, it can be at infinity.
But anyway, the answer to all these concerns is once more of course stitching. Perfect corners guaranteed 100% of the time.
I was thinking that you put the focus where you want it (without recomposing afterwards) and that it does not really matter much if the focal plane is flat or is curved, as long as it is not extremely curved, and as long as you are not shooting flat things. I don't really know how curved it can be though, I haven't seen any measurements, it would be interesting.
In landscape with focus at infinity you typically want large DoF, and I thought it would be large enough to make the curvature effect negligible. But perhaps that is not true?
but will it still be 3::2 format? Ugh! After 4x5, 6x6 ... I just can't get used to the DSLR format anymore.
but will it still be 3::2 format? Ugh! After 4x5, 6x6 ... I just can't get used to the DSLR format anymore.
That my assumption as well, but it seems that on some lenses fild curvature is strong enough that the corners at not focused at infinity when the center is even at f8.
You are going to ask me what lens, are you not? :-)
Cheers,
Bernard
.... But I do see people talking about field curvature issues quite often, I have not just understood which circumstances that this is a problem. ...
The pixel count and angular resolution is more important than pixel size alone: getting the same FOV in a larger format with more pixels of the same size means a longer focal length, so that the same degree of camera movement causes more image movement across the focal plane, so more "pixels-worth" of blur.
I can see that being the case at the image plane. But in a print it doesn't make as much sense. It's similar to the depth of field issue, I think. At the image plane smaller sensored cameras have more DOF but in a print not so because those smaller pixels have to be 'magnified' more to make a print of the same size as a larger sensored camera. It seems the same would be so for 'pixel blur' in this instance.
An image 4800 pixels wide printed at 240DPI will be 20 inch wide, whatever the size of the sensor used to capture the image, right?
Cheers,
Bernard
At the image plane smaller sensored cameras have more DOF
This is true when DoF is by tradition defined with a circle of confusion of 25 microns. This may have been a good definition in the film days when relating to film grain. Today I think it is better to define DoF with a blur spot roughly similar in size to the diffraction blur instead (this is what I use in the field), then you get a DoF definition which is not related to sensor size, but to the actual resolution.
but will it still be 3::2 format? Ugh! After 4x5, 6x6 ... I just can't get used to the DSLR format anymore.
True. But those smaller pixels will need to be 'enlarged' more to make that 20" print. That additional 'enlargement' causes degradation. Whether it's DOF or accentuating camera shake.
I can see that being the case at the image plane. But in a print it doesn't make as much sense. It's similar to the depth of field issue, I think. At the image plane smaller sensored cameras have more DOF but in a print not so because those smaller pixels have to be 'magnified' more to make a print of the same size as a larger sensored camera. It seems the same would be so for 'pixel blur' in this instance.
I don't see that it changes anything regarding technique. Cameras with equivalent (or smaller) pixels already exist on the market and have for several years. A given absolute amount of shake (due to wind, slap, etc.) will have just as much pixel-level blur on these existing cameras.The degree of camera shake and/or subject motion that degrades the resolution of a camera is a fuction of the cameras instantaneous field of view (IFOV) which is basically pixel size/FL. This general has remained about the same for say the 5DII and 7D. For the newer 36MP camera the IFOV would be reduced by sqrt(21/36) or about 1/1.3. So the SS would have to be increased by a similar amount.
Just stitch, crop or keep not using a Dslr. :-)
Cheers,
Bernard
"To a hammer everything looks like a nail" ... and to Bernard everything can be stitched? But Bernard unlike you, I shoot people and things that live and move - except for some art reproduction work. It's not really an option for most of what I do. The only way for me is to crop a lot of the image away, and then what's the point? So while I'd like a camera that does multipoint AF and can shoot a usable ISO 3200, I guess I will stick with my MF cameras for now.
I can see your point. I can see some practical difficulties with it and here's where I come back to the idea of practical concerns. What you're suggesting is a different 'standard' for DOF on an individual camera basis. And again, while I see the point you're making, for the majority of photographers they're not going to be interested in - or perhaps not capable of - making those types of calculations. With that methodology, though, you then run into an issue where DOF begins to become less once you pass the point of diffraction of the lens, right? Is the DOF under that scenario then not also based on the lens, which adds a different variable?
There is only less depth of field with a higher resolution camera if you print larger.
The "old" circle of confusions had nothing to do with film grain, they had everything to do with a standard print size and visual acuity/viewing distance.
What you are proposing is essentially a DOF where the new "standard" print size is 100% pixel view on your monitor at home, so every camera is held to a different standard.
Bob, sorry, but no. A pixel is a pixel and has no memory of how it collected information.
The mathematical truth is that DoF is inversely proportional to the format size, which is easy to confirm with everyday usage of cameras with different formats.
What you probably mean is that:
1. The acceptable circle of confusion also decreases when using a smaller sensor since the pixels become smaller. True also but the impact of this is less than the impact of the increase of the focal lenght.
Per the link below, you can establish that the depth of field is linearly proportional to the circle of confusion (and therefore format) but that it is inversely proportional to the square of the focal lenght.
http://www.bobatkins.com/photography/technical/digitaldof.html
-> the net result is that you do have more DoF in your final image with the smaller format.
2. It takes a higher quality lens to gather equivalent quality light information at the level of each of these pixels. Yes, but on the contrary you need a much smaller image circle, and it is clear that a small image circle of high quality is easier to achieve than a large image circle.
Cheers,
Bernard
But seriously, the camera here in question is the rumoured Nikon D800. I love the D7000 I use right now, but if my intention is to start shooting so that I can make 4 foot by 6 foot prints or have my photos show up on billboards, is the new D800 the way to go?
What other practical needs and considerations in the studio and/or the field does the D800 solve that say a D7000 not address now? For me it's money, do I really need a full frame, 36 MP? What about the rest of you, with the economy the way it is, what need does this camera fill?
What other practical needs and considerations in the studio and/or the field does the D800 solve that say a D7000 not address now? For me it's money, do I really need a full frame, 36 MP? What about the rest of you, with the economy the way it is, what need does this camera fill?
If I can leave all this talk about pixels, lenses, dof, etc, behind and ask a more preactical question - exactly what good will a full frame , 36 MP camera be good for? Let me give you a direct example.
I once met a man who did a lot of stock photography, and his "specialty" was shooting for ads for those large billboards you see beside highways and on the side of buildings, etc. He told me that all things being equal, the larger the sensor AND the higher the MP count, the better. Now I have never shot for billboards so I don't know if this is true or not. My idea of needing detail for large prints is to put away my 4x5 and pull out my 8x10". :)
But seriously, the camera here in question is the rumoured Nikon D800. I love the D7000 I use right now, but if my intention is to start shooting so that I can make 4 foot by 6 foot prints or have my photos show up on billboards, is the new D800 the way to go?
What other practical needs and considerations in the studio and/or the field does the D800 solve that say a D7000 not address now? For me it's money, do I really need a full frame, 36 MP? What about the rest of you, with the economy the way it is, what need does this camera fill?
joe
High resolution does not improve artistry though, but that's not the point. I just like to have the best tools I can afford (assuming it gives visible improvements compared to cheaper tools).
I don't agree with the last point however. I'd say that every camera is held to the same standard - namely to its resolving power. Sure if you know the print size you are going to make you can adapt the required resolution to that, and use that as a reference for CoC, but that would not either translate to a fixed "25 um" CoC (or was it 30 um?), but a different sized CoC depending on print size.
The reason why I use the definition above is that I use the DoF calculations when I want to maximize DoF, get "whole picture sharp" and at the same time maximize resolution (so I can make large prints), and then typically choose between f/8 (typically best corner-to-corner resolution compromise) and the more diffraction limited f/11 or f/16, or tilt the focal plane, or make DoF compromises (let some parts be out of focus). Diffraction limits the resolution somewhat in all cases, therefore I feel that relating the DoF CoC to the airy disc is very relevant and makes the decision process concerning the best aperture and focus placement (and focal plane tilt) more exact. Sure the lens can limit too, especially in the corners so it is not an 100% exact method, but does not need to be and I think it is way better than the fixed size 25 um CoC.
With this method focusing at hyperfocal distance actually becomes usable too (which has got its poor reputation partly due to inadequate DoF definition). Using fixed size 25 um CoC and focus at hyperfocal distance from that those nice mountains in the background won't really be that sharp. For example with 25 um CoC hyperfocal distance is 2.88m with 24mm f/8, but with hyperfocal related to diffraction the distance becomes about 6.7m. Due to difficulty measuring etc using some safe overshoot at ~10m is good, close focus is then at 4m instead of maximum 3.4 which is okay compromise for making sure the distant objects are sharp, I usually prefer some unsharpness in foreground rather than background, since details in foreground is typically larger. Since blurs add up a bit one could argue that CoC should be smaller than airy disc, but I find this a quite ok compromise.
There's nothing wrong with calculating what the diffraction limited aperture will be based on a "per pixel" basis for each camera. It will let you know at what aperture you start to begin to trade resolution for deeper DOF, and help you know how much DOF you will have for a given image if you stick with the diffraction limited aperture at the largest print size. All very good information.
The underlying assumption that go with this method are that you are going to print at the maximum print size possible for your given camera, then view that image at a viewing distance that allows you to see all the way to the "per pixel" detail level. In other words, print as big as you can then viewing the image as close as possible. You could look at it in terms of "print" size, or you could look at is as being the same way that we view images at 100% on the monitor. In jest, you could almost call this the "Pixel Peeper's DOF". :)
The only issue that I have is that it's not a useful as a comparative method between cameras or formats. You can't say that one camera has more DOF or less DOF, since you are subjecting each camera to a different set of viewing conditions based on the camera's capabilities.
You can say that a camera has possibility of less DoF, since the minimum DoF is limited by the lens maximum aperture / focal length combination which tend to be larger for larger formats.
You could also say that a camera has the possibility of less DOF, simply by virtue of the fact that you can make a larger print with it. For example... the D3X has the possibility of less DOF than the D3S (all else equal), simply because you could make a larger print with the D3X and subject it to greater scrutiny than the D3S.
My take on the issue is that DoF simply does not exist...
Not sure I'm following you on that one... looked at the links but am not sure what you are concluding based on your tests.
Another aspect to take into account is lens design. All the models for DoF are based on extremely simplified designs. Actual lenses do behave differently.
The drop of focus as a function of the distance to the perfect plane of sharpness in front and behind the plane of sharpness will therefore be impacted by the design.
Cool, I did not know that. Do you know how large differences can be? Is it quite large, or could it be ignored? A 100% perfect model is not feasible to make of course, the CoC=airy disc model is rather approximate too (airy disc varies with wave length, shape is not same as CoC, two equally sized blurs added forms a slightly larger blur, lens resolving power can be considerably more limiting than diffraction in corners etc), but perhaps the lens DoF differences are so big that they should be taken into account in a DoF model at this approximation level.?
Another aspect to take into account is lens design. All the models for DoF are based on extremely simplified designs. Actual lenses do behave differently.
The drop of focus as a function of the distance to the perfect plane of sharpness in front and behind the plane of sharpness will therefore be impacted by the design.
Cheers,
Bernard
Stitching is like using a larger sensor, exposing one part at a time. I you want large DoF - what you gain (using a large sensor with larger pixels) from being able to use smaller aperture without too much diffraction you lose in the need of using a longer focal length. Mathematically it is exactly the same. An example: for maximum DoF a 36x24mm 36 megapixel sensor with 24mm lens at f/8 is (about) the same as a 36 megapixel 48x36mm medium format sensor with 35mm at f/11.
Ben, really interesting post, and nice photos!Stitching is like using a larger sensor, exposing one part at a time. I you want large DoF - what you gain (using a large sensor with larger pixels) from being able to use smaller aperture without too much diffraction you lose in the need of using a longer focal length. Mathematically it is exactly the same. An example: for maximum DoF a 36x24mm 36 megapixel sensor with 24mm lens at f/8 is (about) the same as a 36 megapixel 48x36mm medium format sensor with 35mm at f/11.
I suppose it's just that with the huge resolution of stitching the lack of DOF becomes more apparent but in that case it would be exactly the same with a higher resolution sensor or in other words, your camera may have 36 megapixels but only up to about f4 or so. That said, if you have to shoot a scene with a D3x at f22 and a D800 at f22 the latter will still give you significantly more resolution for all that it won't be as sharp as it might have been at a lower aperture. Photography is about compromises and sometimes you just gotta stop down...
None of this seems inconsistent with what I'd outlined earlier. In the standard measurement for DOF, assuming two images of the same field of view and same aperture, the DOF will be the same. But at the image plane the digital image will have greater DOF.
Agreed with what you write.
Now, there is something else that comes in the picture, and that is DoF stacking.
With the first example above, it is fairly easy to change the focus point at most areas in the picture to get perfectly sharp images at f8, there is only the area separating the tree from the building behind where DoF stacking would be needed.
Cheers,
Bernard
I suppose it's just that with the huge resolution of stitching the lack of DOF becomes more apparent but in that case it would be exactly the same with a higher resolution sensor or in other words, your camera may have 36 megapixels but only up to about f4 or so. That said, if you have to shoot a scene with a D3x at f22 and a D800 at f22 the latter will still give you significantly more resolution for all that it won't be as sharp as it might have been at a lower aperture. Photography is about compromises and sometimes you just gotta stop down...
f/4 is a bit conservative for a 36MP full frame dSLR. The pixel size would be 4.9 microns and the Airy disc at f/4 with green light is 5.2 microns. If you consider that diffraction comes into play when the Airy disc is 1.4 x the pixel pitch (6.9 microns), you could use f/5.6 with minimal loss. The Airy disc is 7.2 microns at f/5.6.
Are you sure that the D800 at f/22 would have more resolution than the D3x at the same aperture. The Airy disc at f/22 is 28.5 microns and the Dawes limit at f/22 is 91 lp/mm and the Nyquist for the D800 would be 102 lp/mm and 85 lp/mm for the D3x.
Regards,
Bill
You know, Janes, these continual ad hominem remarks really are becoming tiresome.
At the image plane smaller sensored cameras have more DOF but in a print not so because those smaller pixels have to be 'magnified' more to make a print of the same size as a larger sensored camera
True. But those smaller pixels will need to be 'enlarged' more to make that 20" print. That additional 'enlargement' causes degradation.
None of this seems inconsistent with what I'd outlined earlier. In the standard measurement for DOF, assuming two images of the same field of view and same aperture, the DOF will be the same. But at the image plane the digital image will have greater DOF.
How does one reason with another who refuses to use reason?
Bill
Janes, it's not a matter of reasoning. It's a matter not being able to explain yourself clearly. You've provided no explanation of your own for why I'm wrong. You simply point to other sources. I don't actually know if you know what you're talking about or if you're just parroting others. I don't know if you do any of your own work or just blindly read and accept.