Rumors > EOS Bodies

Bokeh difference - full frame vs crop??

(1/4) > >>

Redreflex:
I recall reading somewhere on this forum some comment about how a FF sensor would inherently have better bokeh (or was it shallow depth of field) as compared with a crop. I can no longer find it, and I have since read conflicting opinions elsewhere.

Thus, if an image is captured at the same aperture and full frame equivalent focal lengths on both types of cameras with the same lens, would there be a difference in bokeh and/or depth of field with the 2 different camera types?

If so, is it a theoretical or real difference, and why? Any sample comparison images would be very helpful!

neuroanatomist:
There will be a difference in the depth of field, if you frame the shots identically the FF sensor will give a shallower DoF, by a factor of 1.6 when comparing FF to APS-C.  So, the APS-C will give a depth of field equivalent to setting the aperture on the FF camera 1.3 stops narrower (because stops are a base-2 log scale, and the base-2 log of 1.6 = 1.3).  Put another way, 85mm f/1.2 on a crop body is approximately equivalent to 135mm f/2 on FF, 135mm f/2 on APS-C is approximately equivalent to 200mm f/2.8, etc.  Again, this applies if you frame the shots the same on the two bodies with the same lens. 

The reason is distance - because 85mm on APS-C yields a field of view equivalent to 135mm on FF, to get the same framing you must be further away with the APS-C camera.  That increased distance results in a deeper DoF.

You can prove it to yourself with the numbers, plug whatever you like into DoFMaster's DoF calculator.  They also have a page on the effect of crop on DoF. 

As a side note, this isn't bokeh.  Technically, bokeh is the quality of the OOF blur, and is a property of the lens and the elements in the picture.  A crop sensor affects the quantity of OOF blur. 

Well, ok, that's a simplification, since a crop sensor can affect bokeh with some lenses - in some cases, vignetting results in OOF blur spots at the edge of the frame that have a cat's eye shape, which is less pleasing than a round shape, and to the extent that using an EF lens on a crop body reduces vignetting, it will result in rounder OOF blur spots, which would be considered better bokeh.

Hope that helps...

Mt Spokane Photography:
Neuro, thats one of the best explanations I've seen.  The subject confuses people.  The key is that for the same composition and framing, which means a crop camera is further away.  If the cameras are at the exact same location, the depth of fild will be the same, but the framing will be vastly different.

Bokeh tends to depend on the lens design more than sensor size, it is affected by the aperture setting.

Jamesy:
What Neuro said  ;)

Here are some examples I shot last year with my 40D and a buddies 5D classic. I was most interested in the 40D/50mm vs. 5D/85mm at F2.0 but I also have an example with the 5D/82/f2.0 and 5D/70-200/F4.0.

They are not framed identically but for my purposes, it illustrated the difference between FF and crop.

Woody:
If you want a full blown thesis on the differences between APS-C, FF, 4/3rd etc, you can also take a look here:

http://www.josephjamesphotography.com/equivalence/

Navigation

[0] Message Index

[#] Next page