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-   -   Determining DOF with Canon (and other) AF lenses... (http://www.garageglamour.com/forums/tech-talk-forum/14133-determining-dof-canon-other-af-lenses.html)

RHWeiner 01-08-2005 10:21 PM

Determining DOF with Canon (and other) AF lenses...
 
My old Manual lenses had DOF markings on the lens body itself so I could get some idea of what would/would not be in focus. The new(er) AF lenses don't have that. Any leads for information that would give me an idea of the DOF using these lenses in a shoot?

Thanks,
Richard

R_Fredrick_Smith 01-08-2005 10:48 PM

Re: Determining DOF with Canon (and other) AF lenses...
 
Depends on the Camera. My Canon 20D has a DOF preview button. You just set the exposure (hold down the shutter button half way), then push the DOF preview button and the camera stops down so you can see what the DOF will look like.
Or just get one of the DOF tables and study it for a few minutes and in awhile you'll know what the ranges are pretty well. Here is an example of a DOF shot done by the other method:

http://www.garageglamour.com/portfol..._Smith/763.jpg

cheers,
rfs

dixon 01-08-2005 11:36 PM

link to DOF calculator
 
http://www.dofmaster.com/dofjs.html

dixon 01-08-2005 11:44 PM

DOF shot?
 
Here is an example of a DOF shot done by the other method: . . .

"DOF shot" is rather meaningless. All shots have depth of field--sometimes the DOF is very small/narrow, sometimes it's greater. Your shot, however, doesn't illustrate depth of field--it's an example of selective blurring. Granted, it's an academic point, but when you use specific terms in whatever manner you choose, it creates confusion and hinders clear communication.

R_Fredrick_Smith 01-09-2005 12:58 AM

Re: DOF shot?
 
You'll note that I said DOF done by the "other method". Perhaps I should have included the [img]/ubbthreads/images/graemlins/laugh.gif[/img] icon so my grin was clearer. The "other method" is of course to create the DOF in Photoshop. Naturally I am aware that every shot has DOF and I feel that I used the term "DOF shot" in the context of my intent appropriately. Also my example is a combination of actual DOF, augmented DOF and selected blurring and so, technically, it qualifies as a DOF shot, in any event, but I presented it in the spirit of humor.
I was struck by the humor of the lament over the lack of the DOF scale on the lens. A lot has changed in photography in the last few years and some times I find it amusing to see what people miss the most of those little things that we used to have and take for granted.
Cheers,
rfs

RHWeiner 01-09-2005 03:41 AM

Re: Determining DOF with Canon (and other) AF lenses...
 
[ QUOTE ]
Depends on the Camera. My Canon 20D has a DOF preview button....Or just get one of the DOF tables

[/ QUOTE ]

I'm very familiar with preview buttons as my old Minolta X-700, my Canon A2 and both the Digital Rebel & D30 I've borrowed from time to time have a preview button or function. The problem I have with that is viewing the result through the viewfinder especially when the aperture closes down (?) to show the DOF...image gets so dark as it's difficult to see.

The old lens technology at least gave you somewhat of an indication by checking the markings on the lens itself.

One would think that, given today's autofocus lenses and fairly powerful computing mechanisms in the cameras, you should be able to see what you are going to get as written information in the viewfinder by pressing the release halfway. If the manufacturers can indicate aperture and speed (and other information) there in the base of the viewfinder, surely they can also compute the DOF of a given focal length (obtained via AF) and display that also...before you commit to the shot and fully depress the shutter release? Should be a no-brainer.

I've come across one guy's attempt at providing a DOF guide that can be printed on card stock to take with you. It probably works but I feel you need a manual to figure out how to use the blessed scale.

I guess the only other option is to practice, practice, practice and learn to intuatively know that for a given lens at a given aperture/speed and focal length at a given distance from the subject you are looking at a DOF from 'X' to 'Y' distance. Luckily Digital technology allows for a lot of practice relatively inexpensively...but one still needs to document the parameters of any given shot and then remember the results.

Richard.

RHWeiner 01-09-2005 03:47 AM

Re: link to DOF calculator
 
Thanks for the link...this should help some.


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