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Effect of focal length on depth of field when using a macro extender

Skip70
Enthusiast

What effect do different focal lengths of lenses have on depth-of-field when using a macro extender? Said another way, when using an extender (I don't have a macro lens, I know...) am I going to get more depth of field using a 50mm or 100mm lens.

Bobus question, does aperture have an effect as well?

Thanks. Trying to learn macro on the cheap here!

 

3 REPLIES 3

johnrmoyer
Mentor
Mentor

Depth of Field traditionally includes some concept of print size, viewing distance and human eyesight ability.

The depth of field, once one has a definition for the circle of confusion, is a function of:

  1. distance from sensor to subject
  2. aperture
  3. angle of view (focal length might be used to calculate angle of view)

A macro tube decreases the minimum focus distance. If one uses that closer focus distance, then the depth of field will be reduced.

https://support.usa.canon.com/kb/index?page=content&id=ART157204 "Definition of Permissible Circle of Confusion"

https://www.cambridgeincolour.com/tutorials/depth-of-field.htm Depth of Field

"Note that focal length has not been listed as influencing depth of field, contrary to popular belief. Even though telephoto lenses appear to create a much shallower depth of field, this is mainly because they are often used to magnify the subject when one is unable to get closer. If the subject occupies the same fraction of the image (constant magnification) for both a telephoto and a wide angle lens, the total depth of field is virtually* constant with focal length! This would of course require you to either get much closer with a wide angle lens or much farther with a telephoto lens"

https://www.bhphotovideo.com/explora/photography/tips-and-solutions/the-challenge-of-depth-of-field-... 

 

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https://www.rsok.com/~jrm/

Perhps I misunderstand the role of this forum. It is very disappointing that an administrator changes the title of my post and, in doing so, changes the whole nature of my question. I never asked (in my original title) whether a macro extender affects depth of field; I know it does. I was specifically asking what effect a shorter or longer focal length has on depth of field when using a macro extender. 

Thanks for clarifying!  When I first saw this post, it took me several read-throughs to figure out what was being asked and I wanted to convey it more concisely in the subject line.  I've re-edited it to hew closer to what you asked.

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