Follow Up: Effect of Format Size on DOF


A follow-up to this entry:


We previously showed that Canon was correct to state that increasing format size reduces DOF
Left: 35mm format
Right: APS-C format
Image: Canon Japan


I thought of the following potential additional experimental setup. It is based on the fact that it makes it much easier when you compare much smaller formats with formats much larger. The problem is that I don't own or have access to a Pentax Q10 camera with the 15-45mm f/2.8 lens. The others I do have access to. I even looked to see how much a Q10 with this lens would cost on eBay...but it seems absurd to spend money on a camera just to prove that our current scientific understanding of optics is correct.

Here is the setup:

1. Pentax Q10 camera (5.53× crop factor) with 06 Telephoto Zoom 15-45mm f/2.8 lens (35mmF equivalent of an 83-249mm lens) set at 35mm focal length (35mmF equivalent of 193.5mm focal length)
2. An APS-C camera eg Fuji X camera with a 35mm focal length lens (35mmF equivalent of 53mm focal length)
3. A 35mmF camera (e.g. Canon 5DsR) with a 35mm focal length lens
4. A 4433 medium format camera (eg Fuji GFX50S) with a 35mm focal length lens (35mmF equivalent of a 27.65mm focal length lens)

All cameras set at 35mm absolute focal length, f/2.8, and shooting the same subject with the distance from subject maintained constant. Shooting at 193.5mm effective 35mmF equivalent focal length will give you the shallowest DOF. Shooting at 27.65mm effective 35mmF equivalent focal length will give you the shallowest DOF. Reason: wide angle lenses have shallower DOF than telephoto lenses, no conclusion about format size can be drawn as the experiment is dominated by the effect of angle of view/effective focal length on DOF.

Next compare:

1. 35mm format camera shooting at 193.5mm focal length
2. 35mm format camera shooting at 53mm focal length
3. 35mm format camera shooting at 35mm focal length
4. 35mm format camera shooting at 27.65mm focal length

All cameras set at f/2.8, and shooting the same subject with the distance from subject maintained constant. The longer the focal length the shallower the depth of field will be, just as predicted by the DOF online calculator.

Next compare:

Pentax Q10 camera with the 06 15-45mm f/2.8 lens:

1. Set at 15mm f/2.8
2. Set at 25mm f/2.8
3. Set at 35mm f/2.8
4. Set at 45mm f/2.8

Distance to subject and background kept the same. Repeat the same thing with a 35mmF camera mounted with a 70-200mm f/2.8 lens. You will see that even with the same zoom lens, the longer the focal length, the shallower the DOF. Zooming does not merely "take a crop" of the same image without impacting on the circle of confusion (as would happen when cropping in post-production). You will see more background blur at the telephoto end than at the wide end of the zoom lens. This behaviour is correctly predicted by the online DOF calculator.

Next compare:

1. Pentax Q10 with 01 model 8.5mm lens (35mmF equivalent of a 47mm lens)
2. An APS-C Fuji X camera with a 31mm focal length lens (35mmF equivalent of a 47mm lens)
3. A 35mmF camera with a 47mm lens
4. A 4433 format camera with a 59mm lens

All cameras set at f/4 (there are no native medium format lenses that get you to 59mm f/2.8), and shooting the same subject with the distance from subject maintained constant. Focal lengths like 31mm, 47mm, 59mm set on a zoom lens. You will then conclude that the larger the format, the shallower the DOF, as predicted by the DOF online calculator.

I have also found an alternative DOF calculator:

https://www.photopills.com/calculators/dof

It's a bit user-friendlier and better updated for camera models than the DOF Master calculator. The only caveat is that it lacks the values for the circle of confusion.

Here is also another blog that goes through the same issues as I do and comes to identical conclusions:

https://neilvn.com/tangents/full-frame-vs-crop-sensor-cameras-comparison-depth-of-field/

Notice once again that the author points readers towards a DOF calculator and then asks readers to corroborate whether the calculations are correct.

Comments

Post a Comment

Popular posts from this blog

PROOF that the Larger the Camera Format the Shallower the Depth of Field!

Image
It is a sad fact that today some algorithm ensures the populist proliferation of gross misinformation on the internet. In an age of misinformation being spread like wildfire over the internet, readers are asked to critically evaluate the information they have been presented with: 1. Is the source of information credible? 2. Is it mechanistically plausible (in photography, on the basis of the science of optics)? 3. If objections have been raised, have these objections been adequately dealt with? Sadly, the chances are that the internet will ignore credible sources of information along with science and unquestioningly listen to Suckerberg-type algorithm driven popularisations of egregious falsehoods instead. But despite the chances that all reasoned arguments and scientifically credible evidence will be ignored, proof that the claims made in this YouTube segment are utter nonsense will be shown to the rare thinkers amongst readers: This flies in the face of what Canon st...
Read more

PREDICTION: The Canon 1DX II Successor Will be a Pellicle Mirror Global Shutter Camera

Image
The latest news is that a Canon ambassador has been found talking about an upcoming camera that can shoot at 30fps: https://www.canonrumors.com/a-new-canon-dslr-seems-to-be-getting-teased-on-social-media-by-a-canon-ambassador/ People are commenting that the camera must be designed to shoot at 30fps in the mirror up position, which is totally absurd. That is like saying that the mirror is a redundant piece of equipment that needs to be locked up and forced to get out of the way for the camera to function properly. It is much more likely that the 1DX Mark II successor will have no mechanical reflex mirror but that it will instead have a pellicle mirror. That way, the mirror does not need to be moved out of the way for it to function and contributes positively to the accuracy of the autofocus. Some may wonder if Canon has found a way to get the reflex mirror to move fast enough to achieve a 30fps frame rate, but that is unlikely. At some point, Canon have NO CHOICE but to elim...
Read more

PREDICTION: Canon Will Reintroduce the Pellicle Mirror to their DSLR System

Image
This is a bold prediction, but Canon (and Nikon) will reintroduce the pellicle mirror into their DSLR line camera systems some time within the next 4-8 years. The last pellicle mirror camera released by Canon was the EOS-1N RS introduced in 1995 and only discontinued in 2001: A semi-translucent pellicle mirror replaces a moving reflex mirror that lifts up to capture the image. The key prediction being made here today is that the pellicle mirror will return to a 1D equivalent camera some time in the next 4-8 years. Nikon, in the more distant past, has also had pellicle mirror film cameras like the Nikon F2H from 1976, and they too will introduce a pellicle mirror digital single-lens translucent mirror (DSLT) camera with an electronic viewfinder (EVF) replacing an optical viewfinder. Canon tends to be more conservative than Nikon but in this instance Canon appears to own recent patents relevant to pellicle mirror cameras, whereas no DSLT relevant Nikon patents have be...
Read more