Sensor size and dof - quick test

BacktotheFuji

BacktotheFuji

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Graham
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Firstly this is not a scientific test! More of interest to those perhaps interested/concerned about the dof provided by larger/smaller sensor cameras.

Up until recently most of my photography has been with full frame cameras. But since becoming a father much of my time is now spent shooting the little one, which means dragging along bags full of baby paraphernalia along with all the camera gear! As a consequence I've been experimenting with smaller, lighter mirrorless cameras. Anyway, the results of that are for a different thread. This is about the differences in depth of field provided by the various sizes of sensor available, which has become apparent in normal shooting.

I'm currently shooting with full frame (Canon EOS 6D), aps-c (Fuji X-E1) and micro four thirds cameras (Olympus E-PL5). I wanted to use equivalent "normal" length lenses and I shot the same scene with all three cameras in shutter priority mode at f/2.8 and let the cameras work out the ISO value. I used a Carl Zeiss Planar 50/1.4 with the Canon, Fujinon 35/1.4 with the Fuji and Sigma 30/2.8 with the Olympus. Sadly I don't have a 50mm for the MFT camera so the field of view is slightly different. Interestingly the Fuji's focal length looks slightly longer than 50mm.

Images were all resized down to 3000px wide and a crop taken of the subject for you to inspect the depth of field available.

Full frame - ISO 1250

View attachment 14826

APS-C - ISO 2000

View attachment 14827

MFT - ISO 1600

View attachment 14828

Crops to follow...
 
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manualfocus-g said:
Firstly this is not a scientific test! More of interest to those perhaps interested/concerned about the dof provided by larger/smaller sensor cameras.

...I shot the same scene with all three cameras in shutter priority mode at f/2.8 and let the cameras work out the ISO value.
Click to expand...

For depth of field at the same aperture I suppose that's all fair enough if you want to compare what each system looks like at f2.8 but as the "crop factor" seems to work for focal length and depth of field the results shouldn't be a shock although I personally don't think that the differences at f2.8 are all that significant in these shots. I suppose it'll depend on what you want to achieve and the relationships between the subject and the background.

If trying to get the same depth of field you'd get from a FF setup at 50mm and f2.8 with a smaller system you could do so quite easily by shooting MFT at 25mm and f1.4 (and whatever the numbers are for either x1.5 or x1.6 APS-C) assuming you have the appropriate lens. As some of the smaller sensor lenses are quite good at the widest apertures and indeed wide open that probably shouldn't be a problem.

The following shots are FF and MFT with the focal length and aperture set to take account of the crop factor. There are slight differences in framing as I shot these handheld from a seating position and changed position slightly as I put one camera down and picked up the next but they're near enough to show that the images are essentially the same. Any differences in exposure, contrast or saturation could be easily equalised in processing and the only real differences are how the lens renders.









Personally I see an advantage for smaller sensor systems here as often with FF I'm trying to get deeper DoF to get more of the subject in focus and with smaller systems you can do so with the same or even a faster exposure. ie. If I'm shooting a subject with FF at f2.8 and their face is drifting out of the DoF I can get more DoF shooting with MFT at the same aperture, FF equiv f5.6 DoF, or even with a slightly wider aperture, MFT f2 gives equiv FF f4 DoF. Once you start stopping FF down to f2.8 and smaller the DoF can be equalled by the smaller systems without resorting to exotic wide aperture lenses like the Voigtlander f0.95's etc.
 
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daugirdas said:
So 6D is by far the cleanest with the most pleasing DOF effect. Fuji is acceptable (just), m43 is pretty poor at these settings. Did I miss anything groundbreaking here?
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Yes. You forgot to say that what everyone should be using is a Canon 1D with a manual focus Zeiss lens.
 
woof woof said:
Yes. You forgot to say that what everyone should be using is a Canon 1D with a manual focus Zeiss lens.
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and why would that be or do I need to get some prescriptions maybe? Please enlighten :)
 
Yes. You need a prescription or rather medication. Or superglue. Broken record and all... :D
 
Nothing groundbreaking here I'm afraid, but with more people thinking of downsizing the topic seems to come up more and more. You can slap a faster lens (or open up the existing lens) on any these cameras, but at the same aperture and similar equivalent focal length, the depth of field will vary like the above.

Personally I quite like the ability to get both eyes in focus using a f/1.7 lens on mft, but I'm well aware that I can do the same on ff at f/3.4 with a higher iso, and probably cleaner output. But...the mft camera is a lot lighter to carry :)

The other thing this test shows is how Olympus and in particular Fuji exaggerate their iso ratings somewhat.
 
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woof woof said:
Yes. You need a prescription or rather medication. Or superglue. Broken record and all... :D
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I have some great idea for superglue fine art project if you shall agree to model me for a day :)
 
manualfocus-g said:
Nothing groundbreaking here I'm afraid, but with more people thinking of downsizing the topic seems to come up more and more. You can slap a faster lens (or open up the existing lens) on any these cameras, but at the same aperture and similar equivalent focal length, the depth of field will vary like the above.
Click to expand...
Yup. For a 2x crop camera, 1/2 the focal length and 2x the aperture (or 1/2 the F-number) for an "equivalent looking" photo at anything beyond macro-ish distances. As both Alan and you mentioned, it's actually quite nice shooting wide open and being able to get both eyes in focus (or the shoulders of the camera with the lens front plate in the case of the Contax - the FF has too low a DoF for that photo which spoils it IMHO)....
 
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