Depth of field.?

Question

I have been taking photography courses for about three years now. I consider myself to have a good eye, and have been recommended for AP Photography in my school next year. However, one thing that has never gone too well for me is getting the proper depth of field. When changing aperture, I never notice any change in focus (ie: more in focus when going from f/8-f/16.) Why is this? Shouldn't I see more get in focus when I go from 8-16?

Am I just not understanding a major aspect of DOF?

Answer 1

No, it is not that you don't grasp the concept. As far as DoF is concerned, there isn't much difference between f/8 and f/16. The actual depth between those apertures are too close to notice a significant difference. Two stops don't produce a noticeable difference unless you seek to achieve a specific effect, especially where a more shallow depth is needed. Depending on the lens, focal length and focusing distance, the same is true between f/2.8 and f/5.6 (two stops apart). At f/2.8 my 50mm f/1.8 prime produces a very similar effect that my 18-135mm f/3.5-5.6 does at f/5.6 and the same focal length or higer. The same is true at f/8-16. Those apertures are sometimes referred to as the 'who cares' aperture settings because they are only used to ensure equal depth between a subject and its surroundings when they are at the same focal distance from the lens, so you use those aperture settings when you don't care what the DoF needs to be. I can't tell the difference between f/8 and f/16. Some might, but not me. Who cares? Right?

Answer 2

Here's what I think you're missing:
All modern SLR cameras focus at "wide open" or maximum aperture. So if you have an f/2.8 lens, you'll be seeing f/2.8 through the viewfinder regardless of what your settings are. The aperture window will shrink down as you release the shutter, or if you use the depth-of-field-preview button present on many cameras. If you don't have a DOF preview available, you won't see the DOF effect of aperture until printing/LCD viewing.

Remember that depth-of-field is contingent on aperture, focal length, focal distance, sensor size, etc.... check out

http://www.dofmaster.com/dofjs.html

To play with different settings on a DOF calculator. Under some circumstances (as you approach the hyperfocal distance of a given lens, for instance) you may not notice much difference between f/8 and f/16.

Answer 3

Depth of field when changing you aperture does not mean that you will significantly see this with your eye. where you will see this is in your Photograph when it has been printed. That is how I was able to finally understand I could not always see this through the lens either. What may have been blurry before may now be in focus depth of field is when you allow more light into you lens the more you will capture on film therefor the more depth of field you will have. but the less light you have then the less objects will appear in focus therefore having a smaller depth of field. So remember when you change you aperture you won't see it until you actually print out a side by side comparison. at least that was the only way that I was able to understand how it worked when I was in school. some things people can see and others cannot. so I hope that this helps.

Answer 4

Depth of Field (DOF) is a term used to define that area, in front of and behind your subject, that is in focus. The larger the f-stop used (f1.4, f2, f2.8) the shallower the DOF. In other words, the area in front of and behind your subject will be out of focus. At smaller f-stops (f8, f11, f16) DOF is much deeper.

The lens chosen also has much to do with DOF - a wide angle (10mm, 15mm 24mm) will have substantially more DOF at all f-stops while a longer lens (100mm, 200mm, 300mm) will have less DOF at all f-stops.

The size of the sensor also affects DOF. This is especially true with digicams.

Answer 5

Focal length, distance of subject vs background, aperture etc... You've never really experimented in three years to see the difference? If you've performed some empirical tests and not been able to discern any differences, then photography ain't your bag.