If I put a DX camera and then a FX camera on the same lens, which one would have the greatest depth of field?
Depth of field for DX vs FX
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Turberticus
Well-known member
Neither. FX would just give you a wider viewing angle. I could be wrong...
Cameron T
Well-known member
Yep. Putting it on a dx camera is literally just like if you only used the center part of the FF sensor.
Now, once you start getting into equivalency, things change, but there's a ton of videos out there covering this exact thing.
Now, once you start getting into equivalency, things change, but there's a ton of videos out there covering this exact thing.
aolander
Well-known member
If you changed cameras and stayed at the same distance, DOF would be the same. If you changed cameras and moved the DX camera back to get the same field of view, the DX would then have greater DOF.
If you view them both at the same size, the DX has less DOF. For example you can't get a free lunch by shooting macro from farther away (To get better dof) then cropping in. Check out a dof calculator, keep all the same except switch from DX to FX camera. The calculator assumes same viewing size. The reason the DX has less is the circle of confusion changes as the image is resized.
www.photopills.com
Depth of Field (DoF) calculator | PhotoPills
This Depth of Field (DoF) calculator will help you get the creative control on the design of your photos. Decide the zone of sharpness you need to tell the story you want and get your message across.
www.photopills.com
Trying to get things right
1/ if you move closer to the subject (Correction - should read further away) or use a wider angle lens with DX to get the same angle of view as on FX you get slightly more than 1 stop extra depth of field on DX.
This is because the "circle of confusion" is different between the two formats when enlarging the captured image to make the sharp 10x8 print on which depth of field calculations are based.
Mathematically a 1.42 crop factor (square root of 2) gives a 1 stop increase in depth of field under the above shooting conditions.
The Nikon 1.5 DX crop gives slightly more than 1 stop extra depth of field than a 1.42 crop.
For practical purposes it is usually to assume 1 stop more depth field for DX in the above shooting conditions.
Getting slightly technical for those not mathematically inclined 1.42 multiples by 1.42 gives an answer for practical purposes of 2.
This is why the "exposure difference" between a 1.4x and a 2x converter is 1 stop.
2/ using a longer focal length to obtain more subject magnification has a big reduction effect on depth of field - 2 stops for a 1.4x increase in focal length or 4 stops with a 2x.
See point 4 for what happens with a TC as it is a little different.
Switching from an FX body to a DX body without changing focus distance or angle of view starts by loosing 2 stops depth of field because of the DX enlarged image size.
The two stops loss of depth of field floss for subject magnification with DX is reduced by the DX approximately 1 stop depth of field advantage - with about one stop less residual depth of field shooting this way.
3/ Depending on whether not you change the angle of view or focus distance when switching from FX to DX can result in either about 1 stop more depth of field or 1 about stop less depth of field.
4/ Using a 1.4 x TC is a little different to switching between FX and DX or zooming out without changing focus distance or angle of view.
If you are not technically minded - check depth of field though the viewfinder - and maybe move on
Starting at 100 mm f4 and adding a 1.4x increases focal length and narrows angle of view to 140mm.
However 1
The aperture stays the same physical size - changing from f4 to equivalent f5.6.
f4 to f5.6 gains I stop depth of field.
The narrower magnified angle of view with the 1.4x starts by loosing 2 stops depth of field.
Two stops loss of depth of field for angle of view less 1 stop for f4 becoming f5.6 results in 1 stop less depth of field overall; compared to loosing 2 stops zooming from 100 to 140mm.
However 2
If you own a 70-200 f2.8 you can open the aperture from f4 to f2.8 - loosing 1 stop depth of field and shortening the shutter speed by 1 stop.
When you do this you get the same depth of field as zooming from 100mm to 140mm - with a different shutter time.
Provided you can open up the aperture 1 stop to offset looseing 1 stop shutter speed (due to the 1.4 converter) you get the same depth of field as zooming with a zoom lens from 100 to 140mm.
Summing up using a 1.4x has a slightly different shutter speed/depth of field effect to zooming out with a lens.
However 3
Adding the 1.4 x "everybody knows" looses 1 stop loss of light - increasing shutter time by 1 stop.
When shooting with Nikon in aperture priority mode the shutter time and aperture do not normally change between converter and no converter - even though most know using a converter looses 1 stop of light!
Off topic but partly relevant is that using current Nikon macro lenses normally maintain an infinity exposure combination read out; despite the loss of light that old timers like me know is inevitable by 1:1 magnification
I understand (but cannot find a supporting source) that this is so that Nikon cameras are able retain correct exposure.,
1/ if you move closer to the subject (Correction - should read further away) or use a wider angle lens with DX to get the same angle of view as on FX you get slightly more than 1 stop extra depth of field on DX.
This is because the "circle of confusion" is different between the two formats when enlarging the captured image to make the sharp 10x8 print on which depth of field calculations are based.
Mathematically a 1.42 crop factor (square root of 2) gives a 1 stop increase in depth of field under the above shooting conditions.
The Nikon 1.5 DX crop gives slightly more than 1 stop extra depth of field than a 1.42 crop.
For practical purposes it is usually to assume 1 stop more depth field for DX in the above shooting conditions.
Getting slightly technical for those not mathematically inclined 1.42 multiples by 1.42 gives an answer for practical purposes of 2.
This is why the "exposure difference" between a 1.4x and a 2x converter is 1 stop.
2/ using a longer focal length to obtain more subject magnification has a big reduction effect on depth of field - 2 stops for a 1.4x increase in focal length or 4 stops with a 2x.
See point 4 for what happens with a TC as it is a little different.
Switching from an FX body to a DX body without changing focus distance or angle of view starts by loosing 2 stops depth of field because of the DX enlarged image size.
The two stops loss of depth of field floss for subject magnification with DX is reduced by the DX approximately 1 stop depth of field advantage - with about one stop less residual depth of field shooting this way.
3/ Depending on whether not you change the angle of view or focus distance when switching from FX to DX can result in either about 1 stop more depth of field or 1 about stop less depth of field.
4/ Using a 1.4 x TC is a little different to switching between FX and DX or zooming out without changing focus distance or angle of view.
If you are not technically minded - check depth of field though the viewfinder - and maybe move on
Starting at 100 mm f4 and adding a 1.4x increases focal length and narrows angle of view to 140mm.
However 1
The aperture stays the same physical size - changing from f4 to equivalent f5.6.
f4 to f5.6 gains I stop depth of field.
The narrower magnified angle of view with the 1.4x starts by loosing 2 stops depth of field.
Two stops loss of depth of field for angle of view less 1 stop for f4 becoming f5.6 results in 1 stop less depth of field overall; compared to loosing 2 stops zooming from 100 to 140mm.
However 2
If you own a 70-200 f2.8 you can open the aperture from f4 to f2.8 - loosing 1 stop depth of field and shortening the shutter speed by 1 stop.
When you do this you get the same depth of field as zooming from 100mm to 140mm - with a different shutter time.
Provided you can open up the aperture 1 stop to offset looseing 1 stop shutter speed (due to the 1.4 converter) you get the same depth of field as zooming with a zoom lens from 100 to 140mm.
Summing up using a 1.4x has a slightly different shutter speed/depth of field effect to zooming out with a lens.
However 3
Adding the 1.4 x "everybody knows" looses 1 stop loss of light - increasing shutter time by 1 stop.
When shooting with Nikon in aperture priority mode the shutter time and aperture do not normally change between converter and no converter - even though most know using a converter looses 1 stop of light!
Off topic but partly relevant is that using current Nikon macro lenses normally maintain an infinity exposure combination read out; despite the loss of light that old timers like me know is inevitable by 1:1 magnification
I understand (but cannot find a supporting source) that this is so that Nikon cameras are able retain correct exposure.,
Last edited:
Trying to get things right
1/ if you move closer to the subject or use a wider angle lens with DX to get the same angle of view as on FX you get slightly more than 1 stop extra depth of field on DX.
This is because the "circle of confusion" is different between the two formats when enlarging the captured image to make the sharp 10x8 print on which depth of field calculations are based.
Mathematically a 1.42 crop factor (square root of 2) gives a 1 stop increase in depth of field under the above shooting conditions.
The Nikon 1.5 DX crop gives slightly more than 1 stop extra depth of field than a 1.42 crop.
For practical purposes it is usually to assume 1 stop more depth field for DX in the above shooting conditions.
Getting slightly technical for those not mathematically inclined 1.42 multiples by 1.42 gives an answer for practical purposes of 2.
This is why the "exposure difference" between a 1.4x and a 2x converter is 1 stop.
2/ using a longer focal length to obtain more subject magnification has a big reduction effect on depth of field - 2 stops for a 1.4x increase in focal length or 4 stops with a 2x.
See point 4 for what happens with a TC as it is a little different.
Switching from an FX body to a DX body without changing focus distance or angle of view starts by loosing 2 stops depth of field because of the DX enlarged image size.
The two stops loss of depth of field floss for subject magnification with DX is reduced by the DX approximately 1 stop depth of field advantage - with about one stop less residual depth of field shooting this way.
3/ Depending on whether not you change the angle of view or focus distance when switching from FX to DX can result in either about 1 stop more depth of field or 1 about stop less depth of field.
4/ Using a 1.4 x TC is a little different to switching between FX and DX or zooming out without changing focus distance or angle of view.
If you are not technically minded - check depth of field though the viewfinder - and maybe move on
Starting at 100 mm f4 and adding a 1.4x increases focal length and narrows angle of view to 140mm.
However 1
The aperture stays the same physical size - changing from f4 to equivalent f5.6.
f4 to f5.6 gains I stop depth of field.
The narrower magnified angle of view with the 1.4x starts by loosing 2 stops depth of field.
Two stops loss of depth of field for angle of view less 1 stop for f4 becoming f5.6 results in 1 stop less depth of field overall; compared to loosing 2 stops zooming from 100 to 140mm.
However 2
If you own a 70-200 f2.8 you can open the aperture from f4 to f2.8 - loosing 1 stop depth of field and shortening the shutter speed by 1 stop.
When you do this you get the same depth of field as zooming from 100mm to 140mm - with a different shutter time.
Provided you can open up the aperture 1 stop to offset looseing 1 stop shutter speed (due to the 1.4 converter) you get the same depth of field as zooming with a zoom lens from 100 to 140mm.
Summing up using a 1.4x has a slightly different shutter speed/depth of field effect to zooming out with a lens.
However 3
Adding the 1.4 x "everybody knows" looses 1 stop loss of light - increasing shutter time by 1 stop.
When shooting with Nikon in aperture priority mode the shutter time and aperture do not normally change between converter and no converter - even though most know using a converter looses 1 stop of light!
Off topic but partly relevant is that using current Nikon macro lenses normally maintain an infinity exposure combination read out; despite the loss of light that old timers like me know is inevitable by 1:1 magnification
I understand (but cannot find a supporting source) that this is so that Nikon cameras are able retain correct exposure.,
Your number 1 above doesn't seem to jive with the calculator I linked. Moving closer always resulted in less dof. Same distance but switching to DX also less dof. Perhaps I'm misunderstanding your explanation.
We had good info in this thread:
bcgforums.com
How does crop mode or cropping in post impact subject isolation/DOF?
So I think I know the answer to this question, or at least have an opinion, but I find it interesting. If you shoot in crop mode, or even crop in post, for depth of field purposes do you have to divide your f number by the crop factor?
bcgforums.com
Thanks for spotting my typo.
I have corrected the original in red.
You do of course have to move further back from the subject with DX to get the same angle off view with the same focal length as with FX.
Not corrected from what I see.
Thanks - I have already corrected the original in red.
It should have read further away, not closer.
That's weird. The correction doesn't show up when I look at it. I guess my browser is holding on to the old version of the page. Page refresh doesn't fix it. Oh, well. We get the picture
Same here....That's weird. The correction doesn't show up when I look at it. I guess my browser is holding on to the old version of the page. Page refresh doesn't fix it. Oh, well. We get the picture
fcotterill
Well-known member
YesWe had good info in this thread:
How does crop mode or cropping in post impact subject isolation/DOF?
So I think I know the answer to this question, or at least have an opinion, but I find it interesting. If you shoot in crop mode, or even crop in post, for depth of field purposes do you have to divide your f number by the crop factor?
I'd bookmarked that one and this too. Noise is another linked variable to consider in the equivalence arenaFocal length vs aperture IQ
After some testing between my 600 f4 with and without the 1.4 tc and 800 pf and todays denoise software I wonder which one really has the advantage when it comes to end result image quality. I feel like the closer you can get to your subject even if it’s a stop higher iso it’s a better image...
bcgforums.com
IMHO Spencer Cox from Photographylife has written a decent article about this ...
... and it explains implicitely why it is not the same if I shoot a DX camera of shoot a FX camera in DX mode.
According to these very logical explanations "Small DOF fans" are definitely better off with shooting an FX system and it fits my experience made in times where I thought getting a DX body would help to avoid buying expensive long glass without making a hidden compromise
.
Good example for a welcome but inadmissible simplification of the facts
.In the majority of cases ripping the simplest and most convenient statement out of its context is not really helpful if it comes to find good answers to questions that are not as simpel as some people would like them to be
.
Cameron T
Well-known member
A caveat, shooting DX or a DX crop from an FF sensor is exactly the same once you hit equivalence (fov, etc). The article doesn't dispute that at all, and if you think it did you misread it.IMHO Spencer Cox from Photographylife has written a decent article about this ...
... and it explains implicitely why it is not the same if I shoot a DX camera of shoot a FX camera in DX mode.
According to these very logical explanations "Small DOF fans" are definitely better off with shooting an FX system and it fits my experience made in times where I thought getting a DX body would help to avoid buying expensive long glass without making a hidden compromise
You can prove this with any zoom lens (provided you have a crop sensor and full frame camera both, and the ability to get the equivalent focal length on both). Just follow the chart. Make a test shot at whatever settings with the ff camera, and then take one in crop mode with the settings for the crop body using DX mode. Then take a shot with the actual crop body. They will all look extremely close (of course, slight differences can happen, but they'll be all extremely similar).
The last sentence was correct.
Yup, agree. It's about equivalance between shooting DX and FX in general and there's probably much more to say about it, if one wnats to take it academically.
Considerung making DX crops of a FX images and compare these with direct DX shots with similar FOV is kind of "out of scope". But it is a fact that one of the difference between DX and FX systems is about DOF. So, if we forget about the image resolution, ISO etc., you'll find that if you shoot the same scene with a DX system, then with a FX system and create an image of the FX image with the same FOV by making a DX crop of it, you'll find, that the DX crop of the FX image will show a shallower DOF.
Yes, it looks very similar and many people won't even notice the difference, but it is still not the same. The question is more, whether or not the difference is relevant for what you want to do with the image. For "background blur fanatics" it certainly makes a difference.
Admittedly I currently have no DX body to follow your test procedure, but the good news is, I have been shooting DX and FX bodies side by side since the time of D600, D7000 etc. and all I can say the difference is there.
I agree these comparisons can make the head spin. One difference might be the different pixel dimensions of the two images. If the DX camera has more pixels than the cropped portion of the FX camera, then when viewed on the screen one might be filling the screen with different size images. I don't know but I guess a true test would be to resample one so both are equal pixel dimensions, then see if the DOF is different.
No, it's exactly that simple. There's an entire industry built around making it sound/seem more complicated than it is.Good example for a welcome but inadmissible simplification of the facts
In the majority of cases ripping the simplest and most convenient statement out of its context is not really helpful if it comes to find good answers to questions that are not as simpel as some people would like them to be