DPReview.com is closing April 10th - Find out more

Bokeh samples from same dist. between 200mm @2.8 and 135 @2.0

Started Apr 11, 2013 | Discussions thread
misolo Contributing Member • Posts: 945
Re: Bokeh samples from same dist. between 200mm @2.8 and 135 @2.0

yoms wrote:

Just to clarify: by bokeh I do NOT mean DOF. I can use http://dofmaster.com/dofjs.html to calculate this. It appears that DOF is thinner at 200mm @f/2.8 than 135mm @f/2.0 if subject distance is the same. I am only interested by the look of what is actually OOF in both cases, not in technical/math aspects.

Also, I know that if subject distance is the same, the FOV of a shot at 200mm is narrower than at 135mm. But in real life, this happens too (can't get closer, avoid too much intrusion, etc.) so I really stick to a fixed-distance-from-subject scenario.

Just want to add a note regarding DOF and calculators: If you shoot the 135mm at f/2.0, and then crop to about half the pixel count you will get the same DOF as if the image was taken with a 200mm lens at f/2.8 (well, more precisely 190mm f/2.8).

The reason the calculator gives you different results is that it asumes the printing magnification is the same. When you crop and magnify, you increase the radius of the circle of confusion, which decreases the perceived depth of field.

I'm not sure I understand how you plan to use the lens, but if you're going to use the 135mm in a way that you'll be regularly cropping images (in order to get the field of view of a 200mm), the results from the calculator based on 200/2.8 give you a better sense of the DOF you'll be getting than based on 135/2.0.

 misolo's gear list:misolo's gear list
Canon EOS 5D Mark III Panasonic Lumix DMC-GM1 Canon EF 50mm f/1.2L USM Panasonic Lumix G 20mm F1.7 ASPH Sigma 24mm F1.4 DG HSM Art +13 more
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow