_DoF vs. subject SIZE (NOT distance or focal length)?

[zcai]

According to the DoF calculator http://www.dofmaster.com/dofjs.html , DoF almost has nothing to do with focal length or subject distance?

Compositions usually depend on subject sizes. For a certain subject size and composition wanted, both far distance (more DoF) w/ long focal length (less DoF) and close distance w/ short focal length would work.

Is there any DoF chart available for subject sizes?

 

[ScottyNV]

DOF is dependent on: Focal length, Subject Distance, Aperture of the lens, and Film (Sensor) size/format. the 'subject size' is completely irrelevant..

now, asking a question such as: I'm taking a photo of a car from a distance of 50 feet, using my new XTi.. what focal length and aperture do I need to use to (a) get the whole car within 'DOF' (acceptable sharpness) and (b) keep my shutter speed high enough that I can handhold, and (c) keep the proportions of the car pleasing (no ulrawides, please)??... this is a useful way to frame the question!

hope this helps!
Scotty
--

• How deep does the Rabbit Hole go? *

My XT IS Full Frame -- APS-C/FF of course!

 

[fred vachss]

What DOF really depends on is magnification (i.e. the ratio of subject size to image size) and f number (the ratio of focal length to diameter). You can mess around with all the various parameters as much as you want, but if these two ratios stay the same so will DOF.

 

[zcai]

Thanks for the clear definition! The image size is fixed for my 350D. So the question is:

350D DoF chart for (Subject size, F number)?

What DOF really depends on is magnification (i.e. the ratio of
subject size to image size) and f number (the ratio of focal length
to diameter). You can mess around with all the various parameters
as much as you want, but if these two ratios stay the same so will
DOF.