Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: henrikfoto on May 25, 2008, 04:34:09 pm
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Is it right to assume that the optimum setup to increase depth-of-field would be a sensor with big pixels? Isn´t it correct that these bigger pixels allow smaller f-stops without diffraction than the smaller ones?
So if you don´t need to make very large prints, would you be better of with a 6 or 11 mp digital back than the never ones with pixel-sizes of 9 or 7,2 microns? For example in product photography if you want the depth-of-field to be as large as possible, and would need to work on f22 or higher.
Anybody who knows or have tested? Which of the backs have larges pixels than 9 micron?
Henrik
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Is it right to assume that the optimum setup to increase depth-of-field would be a sensor with big pixels? Isn´t it correct that these bigger pixels allow smaller f-stops without diffraction than the smaller ones?
So if you don´t need to make very large prints, would you be better of with a 6 or 11 mp digital back than the never ones with pixel-sizes of 9 or 7,2 microns? For example in product photography if you want the depth-of-field to be as large as possible, and would need to work on f22 or higher.
Anybody who knows or have tested? Which of the backs have larges pixels than 9 micron?
Henrik
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Henrik,
Pixel size does not have a direct correlation to depth of field from what i know. The size of the overall sensor is what contributes to the difference in depth of field that you see. If you want the greatest depth of field, you would logically be better off shooting with a smaller chip (however, generally you find a decrease in file quality for the same Mpix).
The bigger the sensor/film size is, the shallower the depth of field you will get at the same F-stop.
To reiterate, if you have a 20micron chip spread over 56x56 and a 7 micron chip spread over 56x56, then the depth of field will be the same if they are sampled to the same output size.
If you were very concerned with achieving very large depth of field and the best image quality was not required, i suppose you could consider using a smaller chip size if you were not into using tilt/shift techniques or other workarounds.
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Pixel size DOES affect DOF. Just reduce a 22MP image down to 0.2MP for a web sized image and suddenly the whole image looks to be in focus (unless you have some serious foreground/background blur) because the 'in focus' and 'nearly in focus' areas of the image will both appear in focus at the reduced size. This is exactly how the image would appear if shot on a 0.2MP sensor the same size as the original.
There are disagreements about what constitutes DOF: Personally I find the traditional film-based definition inadequate, and prefer to think of it as what appears in focus when viewed on screen at 100% (traditionalists will no doubt object strongly).
Example. At full size, the DOF is only half a metre. At this size, the whole image looks in focus.
(http://forums.rennlist.com/upload/19bb80a9.jpg)
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Henrik,
Pixel size does not have a direct correlation to depth of field from what i know. The size of the overall sensor is what contributes to the difference in depth of field that you see. If you want the greatest depth of field, you would logically be better off shooting with a smaller chip (however, generally you find a decrease in file quality for the same Mpix).
The bigger the sensor/film size is, the shallower the depth of field you will get at the same F-stop.
To reiterate, if you have a 20micron chip spread over 56x56 and a 7 micron chip spread over 56x56, then the depth of field will be the same if they are sampled to the same output size.
If you were very concerned with achieving very large depth of field and the best image quality was not required, i suppose you could consider using a smaller chip size if you were not into using tilt/shift techniques or other workarounds.
[a href=\"index.php?act=findpost&pid=197928\"][{POST_SNAPBACK}][/a]
Hi!
Thanks, I understand that. What I am really wondering about is if it´s correct that the
larger pixels allow smaller appertures without the same loss of quality caused by diffraction
at the sensor?
I use tilt and shift, but that is not always the solution.
Henrik
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Google on circle of confusion that will give you some information.
And it translates to the webexample also
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Google on circle of confusion that will give you some information.
And it translates to the webexample also
[a href=\"index.php?act=findpost&pid=197937\"][{POST_SNAPBACK}][/a]
Hi Frank!
I know about this, but all never digital lenses are best at f.8 (about), because the pixels they are made for are so small. Used at f.22 or higher the quality of the image hurts. Wouldn´t larger pixels allow these smaller apertures with less quality-loss?
Henrik
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Pixel size DOES affect DOF. Just reduce a 22MP image down to 0.2MP for a web sized image and suddenly the whole image looks to be in focus (unless you have some serious foreground/background blur) because the 'in focus' and 'nearly in focus' areas of the image will both appear in focus at the reduced size. This is exactly how the image would appear if shot on a 0.2MP sensor the same size as the original.
I am by no means an expert on the matter, but i have a hard time believing the circle of confusion on that image accounts for 1/2 meter dof. As mentioned, i am not an expert but i would like to see the exif for the image and such.
As for downsizing images images, pixel size does not effect DOF. In fact, you just said so. The 22mp image downsized to make an even comparison with the .2mp one, both with the same sensor size, will create the same image. Hence, pixel size does not have an effect on dof.
If i am wrong please correct me.
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The DoF depends on the focal length, focusing distance, aperture diameter and circle of confusion. The CoC depends on the pixel size.
Small P&S have large DoF because of the miniscule focal length, which more than makes up for the tiny pixels.
Larger pixels increase the CoC (and thereby the DoF); they tolerate smaller apertures as well (higher diffraction) - however, they yield lower resolution.
The sensor size has nothing to do with DoF but with FoV, the angle of view.
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I am by no means an expert on the matter, but i have a hard time believing the circle of confusion on that image accounts for 1/2 meter dof. As mentioned, i am not an expert but i would like to see the exif for the image and such.
As for downsizing images images, pixel size does not effect DOF. In fact, you just said so. The 22mp image downsized to make an even comparison with the .2mp one, both with the same sensor size, will create the same image. Hence, pixel size does not have an effect on dof.
If i am wrong please correct me.
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No, it should not have a direct effect, but larger pixels should allow smaller appertures and therefore larger DOF??
Henrik
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As for downsizing images images, pixel size does not effect DOF. In fact, you just said so. The 22mp image downsized to make an even comparison with the .2mp one, both with the same sensor size, will create the same image. Hence, pixel size does not have an effect on dof.
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You are comparing a 0.2 MP image with another 0.2MP image
If you printed the 0.2MP image and the 22 MP images at the same size, the 0.2 MP image would appear to be in focus all over. The 22MP image would not.
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The DoF depends on the focal length, focusing distance, aperture diameter and circle of confusion. The CoC depends on the pixel size.
Small P&S have large DoF because of the miniscule focal length, which more than makes up for the tiny pixels.
Larger pixels increase the CoC (and thereby the DoF); they tolerate smaller apertures as well (higher diffraction) - however, they yield lower resolution.
The sensor size has nothing to do with DoF but with FoV, the angle of view.
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But is more than 6 or 11 mp on a mediumformat system needed for prints at A4? Would anybody notice the difference between the newer backs at A4?
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This where you guys lose me. Going back to film. back when I was shooting film, I oftentimes shot a 35mm slide to accompany my 4x5 transparencies. Roughly with lenses of similar FoV, I could shoot at f8 on the 35 to get approximately the same DoF as f22 on the 4x5. If I shot at f22 on the 35, I would have significantly more DoF than the 4x5. I see the same thing on a 30D vs. a 5D.
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This where you guys lose me. Going back to film. back when I was shooting film, I oftentimes shot a 35mm slide to accompany my 4x5 transparencies. Roughly with lenses of similar FoV, I could shoot at f8 on the 35 to get approximately the same DoF as f22 on the 4x5. If I shot at f22 on the 35, I would have significantly more DoF than the 4x5. I see the same thing on a 30D vs. a 5D.
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Kirk, you are comparing different 'sensor' sizes, not 'pixel' sizes.
Actually with the same film stock in both cameras, your pixel size is effectively even, just the sensor size is different.
This thread is about pixel size.
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Kirk, you are comparing different 'sensor' sizes, not 'pixel' sizes.
Actually with the same film stock in both cameras, your pixel size is effectively even, just the sensor size is different.
This thread is about pixel size.
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Would you say that a combination of small sensor-size and large pixels would result in the largest depth-of-field? (combined with small apperture of course)
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when I was shooting film, I oftentimes shot a 35mm slide to accompany my 4x5 transparencies. Roughly with lenses of similar FoV, I could shoot at f8 on the 35 to get approximately the same DoF as f22 on the 4x5
The same FoV on a 4x5 camera requires 1.5 times longer focal length than on the 36mm. Therefor the DoF is less on the MF camera than on the 36mm, assuming the same f-number; you have to compensate for that by smaller aperture.
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You are comparing a 0.2 MP image with another 0.2MP image
If you printed the 0.2MP image and the 22 MP images at the same size, the 0.2 MP image would appear to be in focus all over. The 22MP image would not.
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This is not true.
If i take a 56x56 sensor that is .2mpx and another of the same size that is 22mpx, then when i print it out at the same size, say 4x6, the DOF will be identical.
If not what makes you think so?
The sensor size has nothing to do with DoF but with FoV, the angle of view.
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Agreed, however, in order to have the same fov on 2 cameras with different sensor sizes, you must adjust the lens' focal length. This in effect changes the DOF.
Would you say that a combination of small sensor-size and large pixels would result in the largest depth-of-field? (combined with small apperture of course)
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I would still say that a smaller sensor with the same fov as a larger sensor is the only way to adjust the sensor to get more dof. I am having a very hard time understanding how pixel size changes DOF at all, so if someone knows how it does please explain.
As far as the main question of this topic goes: Would a sensor with larger photosites somehow reduce the diffraction of lenses when stopping down smaller than f22? (i think that is the question) My understanding is that this is a limitation of the lens and not a limitation of the sensor and therefore is not something that can be remedied by changing sensitivity and size of the photosites. The higher the aperture you go to (beyond the optimal point) the less lines the lens will be able to resolve and definition will be lacking. i think.
BTW i still don't understand (nor believe) how larger photosites/pixel determine anything having to do with DOF, so if it does feel free to give me a heads up with a logical explanation.
-b-
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This is not true.
If i take a 56x56 sensor that is .2mpx and another of the same size that is 22mpx, then when i print it out at the same size, say 4x6, the DOF will be identical.
If not what makes you think so?
[a href=\"index.php?act=findpost&pid=197961\"][{POST_SNAPBACK}][/a]
Well I am not sure how to make it any clearer. I have already posted the 0.2MP image, and you can see that the DOF is effectively infinite. Compared to this, the 22MP image printed at the same size would have very sharp details and (relatively) blurred areas. The eye sees the resolution of the sharpest parts on an image and anything less sharp is seen as out of focus. It is a relative measure.
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Well I am not sure how to make it any clearer. I have already posted the 0.2MP image, and you can see that the DOF is effectively infinite. Compared to this, the 22MP image printed at the same size would have very sharp details and (relatively) blurred areas. The eye sees the resolution of the sharpest parts on an image and anything less sharp is seen as out of focus. It is a relative measure.
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What is the exif data for the photo above?
mainly camera, focal length, fstop, and focusing distance/subject distance.
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Agreed, however, in order to have the same fov on 2 cameras with different sensor sizes, you must adjust the lens' focal length. This in effect changes the DOF
It is unhealty for a discussion to mix up different aspects. Stick to narrow subjects, abstracted from others; otherwise we end up with arguments like my eyes are not as good as yours, so the DoF for me is much larger than for you.
I am having a very hard time understanding how pixel size changes DOF at all
Well, then back to the basics.
What does it mean to be in focus? It means, that different light rays from a point of light meet at the focal plane (at the level of the film or sensor). Out of focus means, that the light rays meet before or (imaginarily) after the focal plane; anyway, they arrive at different points on the focal plane.
When these points are so close, that the difference is not perceivable, then we say they are within the circle of confusion.
Thie means with sensors, that as long as the light rays arrive within the "catchment area of the pixel site" (i.e. over the microlens of a single pixel), then one can not differentiate between in-focus and out-of-focus. However, if some of the light rays arrive at other pixels, then that point of light appears to be at several pixels at the same time.
So, the larger the pixel site, the larger difference is tolerable.
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What is the exif data for the photo above?
mainly camera, focal length, fstop, and focusing distance/subject distance.
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The Rollei camera doesn't communicate that info to the back so I don't have any EXIF info.
It is beside the point anyway. No aperture that I could have used could get all of that image in equally good focus across 22 MP.
The 22MP v 0.2 MP example is an extreme one, but just demonstrates clearly the effect that pixel size has on focus.
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Here is a 100% crop from the 22MP image, where you can clearly see the areas of the image which are in and out of focus.
[attachment=6772:attachment]
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I think this discussion is getting a bit confused. What I think Henrik is referring to is image sharpness lost due to small aperture diffraction not depth of field, which are two different things.
Does pixel size, density, and design have an effect on the diffraction effects (softening) of small lens apertures required for maximum DOF ?
- Why with digital it seems the diffraction effects that shows when stopped down to f-22 to obtain the required DOF the critical focused point of an image does not look as sharp as the would be at f8 compared with past film experiences?
- Why with digital when one applies camera movements you seem to lose more sharpness at the critical focused point compared with no movements, as compared to past film experiences?
One non pixel related answer is that even with film there was such effects. We only inspected our transparencies with 10x magnification, and not at the type of magnification digital allows.
At present there would seem to be a direct relationship between pixel size, density in the chip, and pixel design in images degrading in sharpness due to diffraction with smaller apertures and or with technical camera movements. If the pixels properties were not an issue at all the P31+ and Blads 31mpx chips would work great with wide angle lens and technical camera movements.
I know I had less effects from camera movements with my older Sinar H23 back as compared to the Blad 528C back.
I have however seen examples, and tested it to be correct, that if you critically focus on one point wide open and then stop down and shoot, this point will not be as sharp as if you refocus on the exact same point at f22. Is this an effect of digital pixels , or a lens effect? I never tried it with film so I have no idea.
The big question, and Henrik's question is if real life research / testing has been done and if there are any results available to the public?
Brent Daniels
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I would venture to suggest, at the risk of getting vilified, that having fewer but larger pixels on the same size sensor can contribute to an appearance of greater DoF, depending on print size and viewing distance.
As Graham has suggested, downsizing the image which has more pixels to the same size as the image with fewer pixels, sort of equalizes DoF in both images.
But what happens if you upsize the image with fewer pixels, through interpolation, to the same size as the other image? In those circumstances, the image that started off with fewer pixels might appear to have greater DoF because the sharpness at the plane of focus will be less (than that in the image with initially more pixels) and will be closer to the sharpness of the rest of the image (in both images) which is not in the plane of focus.
Downsizing the image which has the greater number of pixels results in a discarding of resolution at the plane of focus, but no discarding, or less discarding of resolution away from the plane of focus.
Upsizing the image with fewer pixels is probably a fairer comparison because no information is thrown away in either image.
However, there might be a problem with the definition of DoF if it includes phrases such as 'acceptable sharpness'. To take an extreme example, a large print from a pin-hole camera might have amazing DoF, everything being equally sharp (or fuzzy) from one's feet to infinity. Pin-hole cameras are noted for their great DoF.
If nothing in the print is acceptably sharp, does that have a bearing on DoF? If you were to take a slightly fuzzy, image from a pinhole camera, digitise it and then through photoshop manipulation, seamlessly plant a sharp object ( figure, face, tree, whatever) in the middle of the image (or replace a relatively small object already in the image with a sharper version), would we have converted an image that we previously considered to have great (extensive) DoF into one which now has shallow DoF?
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It is unhealty for a discussion to mix up different aspects. Stick to narrow subjects, abstracted from others; otherwise we end up with arguments like my eyes are not as good as yours, so the DoF for me is much larger than for you.
Well, then back to the basics.
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Thie means with sensors, that as long as the light rays arrive within the "catchment area of the pixel site" (i.e. over the microlens of a single pixel), then one can not differentiate between in-focus and out-of-focus. However, if some of the light rays arrive at other pixels, then that point of light appears to be at several pixels at the same time.
So, the larger the pixel site, the larger difference is tolerable.
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As you mention, this topic has, like almost all, become (in great part do to myself, sorry) a multi-faceted conversation. So yeah, this will be my last response and if anyone does care to discuss the effects of pixel density on DOF further, please message me. Whether i be right or wrong I am always up for learning and listening, especially when i am wrong.
In regards to larger pixels taking multiple rays of light and therefore decreasing dof: While the gradient between in focus and out of focus will not be as smooth on the higher mpx chip, the amount between in focus and out of focus will remain the same. The DOF is inversely proportional to sensor size and, physics wise, doesn't have anything to do with pixel density. The only difference is in smoothness of in/out of focus gradation.
thanks for your replies and such,
-b-
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In regards to larger pixels taking multiple rays of light and therefore decreasing dof:
The larger pixel size increases the DoF.
The DOF is inversely proportional to sensor size
No relationship whatsoever.
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The larger pixel size increases the DoF.
No relationship whatsoever.
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ok, within the limitation to them having the same fov this is true.
"More precisely, if photographs with the same final-image size are taken in two different camera formats at the same subject distance with the same field of view and f-number, the DOF is, to a first approximation, inversely proportional to the format size. "
makes sense to me, no?
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ok, within the limitation to them having the same fov this is true.
"More precisely, if photographs with the same final-image size are taken in two different camera formats at the same subject distance with the same field of view and f-number, the DOF is, to a first approximation, inversely proportional to the format size. "
makes sense to me, no?
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Makes sense to me also, but in digital imaging the size of the unaltered image depends on the number of pixels not the size of the pixels nor the size of the sensor. So in my view, the different number of pixels on two sensors of the same size can affect the appearance of DoF, depending on how those two images are processed and what size prints are produced.
Lens sharpness will also have a significant role to play. If the lens used with both cameras of equal sensor size but unequal pixel count are simply not good enough to deliver that additional resolution that the sensor of higher pixel count is potentially capable of, then DoF differences would probably be negligible.
In any case, such differences due to pixel count would be a secondary concern. However, it would be an interesting experiment to make if one had nothing better to do. I would think that comparing differences of less than double the pixel count might be a waste of time. Comparing a D30 with a 40D, or a D60 with a 450D, or a 1Ds with 1Ds3 might produce some worthwhile differences in DoF, using both high quality primes and low quality zooms.
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We are talking digital imaging.
A digital image is a digital image is a digital image... not a piece of paper, not a monotor, nothing upresed or downresed. A digital image consists of pixels, and that's it.
A point of light is out of focus if its image appears in several pixels. This has nothing to do with feld of view, sensor size, print size, etc. Otherwise the entire discussion is total nonsense. You print with 360ppi, I print with 300ppi. You look at it from far, I look at it from close. Your eyes are good, mine are bad. You denoise it, I don't. Your monitor has a 72dpi, my one has 96dpi. And so on.
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We are talking digital imaging.
A digital image is a digital image is a digital image... not a piece of paper, not a monotor, nothing upresed or downresed. A digital image consists of pixels, and that's it.
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Gabor,
Whilst all my digital images exist in some file format of one sort or another, DoF is only apparent on a monitor or on a print after the file has undergone some degree of processing.
Having more pixels without changing the sensor size can never reduce resolution in any part of the image, but it can increase resolution in the plane of focus.
I take two shots of a face with the same high quality lens, one with a 3mp D30 and the other with the 10mp 40D. I use an aperture such that the nose is perceptibly OoF in the 40D shot but the eyes are exactly in focus.
I take the same shot with the D30, focussing on the eyes so that the nose is perceptibly OoF, just as in the 40D shot.
I uprezz the D30 image to the same size as the 40D image and make equal size prints. I view both prints from as close as I like. What do I see?
I see the nose in both shots as being equally sharp, but the eys in the 40D shot will be sharper (10mp at the plane of focus has to be sharper than 3mp, with a good lens, or what's the point?).
In the 10mp 40D shot, I get a sense of a slightly shallow DoF (because the nose is less sharp than the eys). In the 3mp D30 shot there is no sense of a shallow DoF. The eyes and nose are both equally sharp.
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The sensor well size does affect DOF in that the use of small apertures is limited by smaller sensor wells. In other words the diffraction is noticeable sooner the smaller the well. The new canon 1Ds3 for example will probably not be as good for macro work as the original 1D since you can stop down to f/11 or f/16 before really noticing the diffraction while you see the diffraction with the 1Ds3 at f/6.8 - so because you can stop down further you can get more apparent DOF.
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Increased pixel size means lower resolution for any given format/sensor size. Lower resolution, when viewed at 100% magnification, is the equvilalent of a smaller print size in comparison to a higher resolution imaging device.
Since larger pixel size means lower resolution (for a given format size), YES it will be less susceptible to diffraction and will allow for a smaller f stop before diffraction negatively affects the resolution of the imaging system. HOWEVER, a smaller pixel size can produce the same resolution at the same f stop, but can also produce higher resolution when shot at more wide open f stops. Diffraction limited is diffraction limited, regardless of how big your pixel size is.
The applicable COC is determined by enlargement factor. Enlargement factor is determined by how big your original format size is relative to your final print size. So, the things that really matter for DOF are 1) Format/Sensor size. 2) Final print size. 3) Focal length. 4) Aperture. 5) Focus Distance.
If your DOF standard is how the image looks at 100%, then pixel size matters - primarily because larger pixel size means less resolution, and less resolution means a smaller effective print size (if your print size is 100% view). That smaller print size means more DOF.
If you equalize the resolution (same megapixels) but compare larger vs. smaller pixel sizes, you mess with all the variables, because now you have different format sizes which require different focal lengths. The longer focal length required by the larger format will lead to a smaller DOF for the larger format, hence the "rule" that larger formats have less DOF.
If you use the same format size and compare large pixels vs. small pixels (low res vs. higher res), then you really need to compare similar print sizes. This means not printing the higher res image at its maximum print size but limiting it to the resolution of the low res/large pixel system. Given equal print sizes, the DOF will be the same. If you increase print size, the DOF of the high resolution/small pixel system will be less. However, this is because of the larger print size, not because of the smaller pixels.
Anyhow, all this said, larger pixel size does not gain you anything other than a resolution limitation, or forcing you into a larger format size.
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... and I would like to add, on the "observing/viewing distance" of the final output.
Thierry
The DoF depends on the focal length, focusing distance, aperture diameter and circle of confusion. The CoC depends on the pixel size.
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As Thierry mentioned it's all in the viewing distances.
First off all DOF is determined by the lens you are using.
That's why you will have much less DOF on a MF system than on a DSLR and even more on a P&S.
Although you will have a similair scene (although they will differ in FOV) the MF will have less DOF than the FF DSLR which will have less than the Crop DSLR etc.
This is mainly due to the difference in lens.
On the MF you will use a 80mm on the FF DSLR a 50mm on the crop a 32mm.
Now take into consideration the Circle of Confusion.
This is connected to the printsize and viewing distance.
The crop that is shown does show less DOF than the full picture, but that's logical because the crop is the same size as the whole downsized picture, meaning the printsize (the pixels) has gone up but the viewing distance is the same (your eyes to the monitor).
For me this was the reason to switch to MF, I love to work with shallow DOF on some occasions and with the DSLR system I had to switch to long lenses or ridicilous large apertures.
With the MF system I can just drop the ISO to 25 and use smaller apertures and still get the same results.
In that case it's all in the longer lenses you can use without changing the distance to the model.
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The sensor well size does affect DOF in that the use of small apertures is limited by smaller sensor wells. In other words the diffraction is noticeable sooner the smaller the well. The new canon 1Ds3 for example will probably not be as good for macro work as the original 1D since you can stop down to f/11 or f/16 before really noticing the diffraction while you see the diffraction with the 1Ds3 at f/6.8 - so because you can stop down further you can get more apparent DOF.
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Thank you, Eric! This was really what my question was about. All the newer digital lenses (like the Apo Sironar Digital HR lenses) are best at f8 or close to that. When you go to smaller appertures the lenses are not as good. As I undersand these lenses are made like that because the smaller pixels of the modern sensors don´t work that well with these small appertures. As a result of this we have less depth-of-field because the use of f-stops above f16 (or even lower) are limited.
Anybody agree on this?
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Example. At full size, the DOF is only half a metre. At this size, the whole image looks in focus.
(http://forums.rennlist.com/upload/19bb80a9.jpg)
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The smaller the image is viewed, or the further away, the more apparent depth of field. It's all to do with COCs, not sensor or pixel size in this case.
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The smaller the image is viewed, or the further away, the more apparent depth of field. It's all to do with COCs, not sensor or pixel size in this case.
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No matter how much large you print that image or how closely you view it, the even focus will still be there.
It is complicated by the fact that there are several limiting factors. If the resolution is high enough, then viewing distance and print size comes into play.
Perhaps it would be more accurate to say that for a given print size and viewing distance, there will be a pixel size limit above which the DOF will visibly widen.
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I'm with Nick, your reducing the size of image to a lower MP size is a red herring in the context of OP's question. Effectively you've moved yourself further away from the image as it's now smaller and that is why you now cannot percieve the OoF aspects of image. DoF is determined not only when you take photo but how you view it. Acceptable DoF depends on how big/small you print/display image and how far away you view it.
Plus with downsizing, the sharp parts of image are degraded so there is less contrast between them and the originally much less sharper parts of image.
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But this is all aoutside the topic. The question was the relationship between the sensors pixelsize and possibility to use smaller apperture, and thereby increased DOF.
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Is it right to assume that the optimum setup to increase depth-of-field would be a sensor with big pixels?
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At dofmaster.com, the online calculator produces the same results for hyperfocal distance and depth of field for the Canon 20D, 30D, 40D which have the same size sensor but increasing number of pixels. Likewise, calculations for the Canon G series digicam from G1 to G9 produce the same results even though the number of pixels in the sensor has increased over the years. In these calculations, the Circle of Confusion is assigned according to some logic or other.
Now, I don't know enough about the details to know if the calculations are correct but I do know enough about DOF and Circle of Confusion to realize that this is a highly discussed and debated topic. It seems to me that the classic calculation is based on enlargement and not number of pixels. In the good old days, the depth of field scale on a lens did not vary with the film speed or resolution.
So my bet is that, to the first approximation, the amount of enlargement -- as related to sensor size -- is the most significant parameter.
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At dofmaster.com, the online calculator produces the same results for hyperfocal distance and depth of field for the Canon 20D, 30D, 40D which have the same size sensor but increasing number of pixels. Likewise, calculations for the Canon G series digicam from G1 to G9 produce the same results even though the number of pixels in the sensor has increased over the years. In these calculations, the Circle of Confusion is assigned according to some logic or other.
Now, I don't know enough about the details to know if the calculations are correct but I do know enough about DOF and Circle of Confusion to realize that this is a highly discussed and debated topic. It seems to me that the classic calculation is based on enlargement and not number of pixels. In the good old days, the depth of field scale on a lens did not vary with the film speed or resolution.
So my bet is that, to the first approximation, the amount of enlargement -- as related to sensor size -- is the most significant parameter.
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I can't see what the confusion is here. People buy cameras with increasingly greater pixel count because they hope to get higher resolution. You can't get higher resolution at small apertures where the lens is limited by diffraction. The higher the pixel count (on the same size sensor), the better the lens needs to be in order to achieve that higher resolution.
Having achieved your higher resolution, by either stopping up to a bigger aperture which is less affected by diffraction, or by using a better lens, a print from the image with the higher resolution must have a shallower DoF than the same size print from the lower resolution image, assuming the same lens was used at the same aperture and same distance to subject.
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It appears that doubling the number of pixels on a full frame 35mm sensor only costs about one f-stop with respect to diffraction, see
http://www.cambridgeincolour.com/tutorials...sensor-size.htm (http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm)
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It appears that doubling the number of pixels on a full frame 35mm sensor only costs about one f-stop with respect to diffraction, see
http://www.cambridgeincolour.com/tutorials...sensor-size.htm (http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm)
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That makes sense to me provided one is working within a range of diffraction limited f stops. A doubling of pixel count increases the resolution potential of the sensor by 1.4x. Moving up from a diffraction limited F22 to a diffraction limited F16 increases the resolution of the lens by 1.4x. However, stopping up from F4 to F2.8 might not provide any resolution increase. With some lenses one might lose resolution at F2.8.
I think the concept here is, one presumably uses a camera with a greater pixel count in order to achieve greater resolution. If one fails to achieve greater resolution because one's lenses are not good enough, or because the f stop chosen is too limited by diffraction, or because it's too limited by various types of aberrations at wide apertures, then the increased pixel count will not affect the perception of DoF. You might as well have taken the shot with the lower pixel camera, regarding over all sharpness and DoF.
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I think the concept here is, one presumably uses a camera with a greater pixel count in order to achieve greater resolution. If one fails to achieve greater resolution because one's lenses are not good enough, or because the f stop chosen is too limited by diffraction, or because it's too limited by various types of aberrations at wide apertures, then the increased pixel count will not affect the perception of DoF. You might as well have taken the shot with the lower pixel camera, regarding over all sharpness and DoF.
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This almost makes sense but if it was true there would never have been any reason to shoot large format, film or digital.
What you are forgetting is that large format lenses have longer focal lengths for a given FOV. This means that at any given aperture (ratio of iris size to focal length) the iris size is bigger and thus proportionately less affected by diffraction error. The same diffraction error would be found at a much smaller f-stop with correspondingly greater DOF. I suspect the two cancel out leaving the result that the larger the format the better image Q at any given output size and at any given pixel density or film type.
That's why LF, sensor or film, gives generally better results.
Edit : I misread your post, too hasty - you don't mention sensor size and thus I agree with you.
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It appears that doubling the number of pixels on a full frame 35mm sensor only costs about one f-stop with respect to diffraction, see
http://www.cambridgeincolour.com/tutorials...sensor-size.htm (http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm)
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Yes, I played with that too and found about 1.5 stops advantage to a 39mp 645 sensor over a 35mm size 22mp sensor with respect to diffraction limits.
Using the DOF calculators it seems that this is more than enough to counter the effects of longer focal length on the bigger sensor so at any given print size and viewing distance the bigger sensor will have twice as many pixels representing the image with much the same apparent DOF. This will equate to better quality prints over a certain size, with roughly equal DOF .
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Edit : I misread your post, too hasty - you don't mention sensor size and thus I agree with you.
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Well, thanks Nick . I think there is some confusion in this thread between the two sets of circumstances, (1) a bigger sensor with more pixels and (2) the same size sensor with more pixels. The OP is asking about the DoF consequences of increasing pixel count on the same size sensor.
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Here's an amusing and nearly pertinent quotation from the Leica Manual, of 1938:
"If you really want to look at the picture you will never hold an enlargement of 8 x 10 inches closer than 10 inches from the eye. Only grain fiends have a habit of smelling their pictures, regardless of size."
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that's exactly the point: the viewing distance. The same when I used to see photographers using a loupe to check their sharpness on a 4x5" transparency (or on any other format), when there is an optimal viewing distance for a film/print which defines the CoC/DoF. Of course, with digital it is impossible to control or view an image on the sensor, but the optimal viewing distance of the output is still part of the definition of sharpness/DoF.
Thierry
Here's an amusing and nearly pertinent quotation from the Leica Manual, of 1938:
"If you really want to look at the picture you will never hold an enlargement of 8 x 10 inches closer than 10 inches from the eye. Only grain fiends have a habit of smelling their pictures, regardless of size."
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Using more, smaller pixels will not reduce decrease depth of field or decrease resolution when using the same aperture ratio so long as one compares with prints of the same size viewed from the same distance. Diffraction only reduces the extent of the resolution/sharpness/detail improvements that one gets at any given aperture from increased sensor resolution (smaller pixel size.)
Any apparent DOF increase at equal aperture attributed to using fewer, larger pixels is really an effect of viewing a smaller version of the lower pixel count image, like prints at the same PPI. You can increase DOF equally well by making equally small prints from a sensor with more, smaller pixels.
Pardon me if I repeat so often the dogma that the only image quality comparisons that matter are ones based on viewing at equal apparent image size (e.g. same print size and viewing distance, or to put on my propellor beanie, equal angular size for the image of the same subject.)
Ignoring this and instead comparing at different image sizes (like equal PPI, as with 100% on screen) leads to various misleading claims for benefits from lower sensor resolution, the likes of which I never heard in the film era.
P. S. Gordon, thanks for the wonderful Leica manual quote!
(It resembles my personal guideline of not closer than 15" from prints 11"x14" and bigger. Going closer is mainly to compensate for "undersized" prints, as 15" is a rough typical minimum comfortable viewing distance; a favorite for reading, for example. Maybe fitting a comfortable 15" or more viewing distance is part of why print sizes like 13"x19" and 16"x20" are popular for galleries.)
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the likes of which I never heard in the film era
This one takes an eminent place amongst the arguments made on this thread. I wonder, why you have not distributed this post per snail mail or telex - there were no internet forums in those days, were there?
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This one takes an eminent place amongst the arguments made on this thread. I wonder, why you have not distributed this post per snail mail or telex - there were no internet forums in those days, were there?
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You have taken a fragment out of a paragraph, thus rendering it meaningless without the full context. Whereas in the complete paragraph it was actually quite a sensible thing to say and was certainly not anti-progress in meaning, as it simply put pixel peeping in context.
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when there is an optimal viewing distance for a film/print which defines the CoC/DoF.
Thiery
I am one of those guys. It is that depth of detail in Large Format that is part of its attraction. I frankly could care less about any so called "optimal viewing distance". I look at my finished prints with a loupe or strong reading glasses and do the same at shows by Ansel Adams or Weston. There is a real different experience between a fine print and a billboard.
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Any apparent DOF increase at equal aperture attributed to using fewer, larger pixels is really an effect of viewing a smaller version of the lower pixel count image, like prints at the same PPI. You can increase DOF equally well by making equally small prints from a sensor with more, smaller pixels.
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Yes, but it is also true that the apparent increase in DoF in the smaller image and smaller print still holds if the smaller image is interpolated to the same size as the larger image, unless all parts of both images appear equally sharp whatever the size, which might be the case if one had used a very small aperture for both shots and/or the scene photographed did not have great depth.
The DoF calculators, such as DoF Master, do not make it clear that the CoC used in their calculations is valid only for a fixed size print (which I believe is 8x10").
When one upgrades one's camera to one with more pixels, keeping the format size the same, the reason is presumably to enable one to make larger prints which are still acceptably sharp.
If one then views the larger print from a proportionally greater distance, the appearance of DoF will remain unchanged. In that sense, pixel count has no bearing on DoF.
One might therefore conclude that the main purpose of using a camera with a high pixel count is so that one can appreciate fine detail from a closer distance than one would normally view the print when appreciating the composition as a whole.
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Yes, like many others, including myself, but not to "check" and adjust DoF.
But in this case any definition of sharpness and depth of field does not make any sense, respectively is changed by the observer/viewer.
Best regards,
Thierry
Thiery
I am one of those guys. It is that depth of detail in Large Format that is part of its attraction. I frankly could care less about any so called "optimal viewing distance". I look at my finished prints with a loupe or strong reading glasses and do the same at shows by Ansel Adams or Weston. There is a real different experience between a fine print and a billboard.
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Thierry!
Can you tell me the size of the pixels of the older Sinarbacks like the 23 HR?
I couldn´t find it on the net.
Henrik
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Dear Henrik,
the pixel size of the 6 MPx Philips CCD sensor was 12 micros.
Best regards,
Thierry
Thierry!
Can you tell me the size of the pixels of the older Sinarbacks like the 23 HR?
I couldn´t find it on the net.
Henrik
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Dear Henrik,
the pixel size of the 6 MPx Philips CCD sensor was 12 micros.
Best regards,
Thierry
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Thanks a lot, Thierry!
Henrik
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When one upgrades one's camera to one with more pixels, keeping the format size the same, the reason is presumably to enable one to make larger prints which are still acceptably sharp.
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Indeed. Let me put it this way: a sensor with higher pixel count through more, smaller photosites on the same sensor size gives the option of seeing more detail in the image, and that option comes with less DOF. So when one aims to use the greater detail and also wants adequate DOF, this must be accounted for in choice of aperture: smaller apertures are needed. And thus, getting the maximum possible detail from the higher resolution sensor imposes a lower maximum DOF.
But one is never forced to accept lower DOF than is possible with a lower resolution sensor, since there is also the option of not using the extra detail, for example by printing and viewing in the same way as one would with the lower resolution option, perhaps downsampling first.
And therefore, choosing a sensor of lower resolution does not add anything to one's DOF or related IQ options: it simply discards some options for more detail combined with less DOF.
More generally, I still have not seen any good evidence or arguments that higher pixel count sensors cannot match or outdo the results of lower pixel count sensors of the same size with suitable processing or presentation. The processing needed might be as simple as converting to JPEG (or TIFF) at about the same pixel count as the lower resolution sensor.
Or maybe conversion to JPEG at a somewhat lower pixel count than the lower resolution sensor, since in JPEG's of equal pixel count from Bayer CFA sensors, those from a higher pixel count sensor can have a detail advantage, due to less loss of resolution in the demosaicing interpolation.