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DPChallenge Forums >> Tips, Tricks, and Q&A >> Depth of Field
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06/07/2003 12:46:45 PM · #1
I know what DOF is, and I know how to use it properly, but I get confused sometimes when people start talking about.

If someone talks about "minimum" or "maximum" depth of field -- or "more" DOF/"less" DOF -- which is which?

Thanks for the clarification. :)
06/07/2003 01:32:49 PM · #2
DOF is just an acronym for depth of field

so when someone says 'less DOF,' they are saying 'less depth of field' . When you have the least possible, then you are at your minimum DOF :).

conversely, 'more DOF' = 'more depth of field'. Maximum DOF is as much depth of field as your camera would allow.

The part that's probably confusing you is that people refer to an aperture value with a bigger number, i.e. f/16, as being a smaller aperture (than say f/4).

That's because the aperture number is actually the denominator of a fraction. When you have an f/16, you're really saying 'the hole letting in light is 1/16th the focal length of the lens.' When you say it like that you can clearly see that 1/16th of the focal length is a LOT smaller than 1/4 of it (which is what f/4 is).

f/2 would be like saying 'the hole letting in light is 1/2 the focal length of the lens.' That's a big aperture, even tho it's number (f/2) is small.

That help any? :)

Message edited by author 2003-06-07 13:34:08.
06/07/2003 01:46:32 PM · #3
Here are some examples.

Minimum DOF. Only one sliver of grass toward the front of the photo is in sharp focus.
//www.dpchallenge.com/image.php?IMAGE_ID=3605

Maximum DOF. Everything in the photo, from the rocks in front to the hillside in the back are in focus.
//www.dpchallenge.com/image.php?IMAGE_ID=10188

Message edited by author 2003-06-07 13:47:43.
06/07/2003 02:27:47 PM · #4
I got it now. Being a visually oriented, once I get the concept, I figure out a visual gimmick so I won't forget it again.

When the dentist says, "Open wide" and looks at my whole mouth, that's maximum depth of field. When he takes that drill and zeros in on the cavity in ONE tooth, that's minimum depth of field.

That may make not a whit of sense to anyone else, but that's how I will remember the concept easily.

As for aperture, I have NEVER been able to grasp the technicalities of how it works, but did I grasp the concept when I studied it long ago that the lower the f-stop, the more light I'm letting into the camera.

I like your explanation of it though, mag. -- it's a lot clearer the way you say it than any way I've ever heard it before.

Thanks, guys. :)
06/07/2003 03:06:15 PM · #5
sometimes it can help to look at an SLR lens and change the f number and snap a shot off so you can see how big or small the iris opens up. it took me some time to understand it and I still have a problem with it sometimes....small f# = big opening , big f# = small opening. sometimes I wish I could find the guy who came up with that concept and strangel him for making it so confusing....but im sure the math makes it work some how....

James
06/07/2003 04:27:56 PM · #6
i dunno. i took to my slr (nikon fm2/n, nikkor 50mm 1:1.8) like a fish to water. then again, i grew up in a photographer's household, always having a camera which was more or less exactly the same, only pointed at me.

to ease the confusion, more depth of field is just that: more depth. meaning, more of the picture is in focus. the plane that the lens focuses on is larger, and this comes with smaller aperature (larger number) and requires a longer shutter speed (smaller number) to produce the same exposure as larger aperature and faster shutter speed, which has smaller (or "poorer") depth of field.

but, don't let the people on here fool you -- small depth of field DOES have its uses and can be quite beneficial in directing the viewer to a particular center of focus in your image. (or as someone demonstrated earlier, removing objects entirely, like the fence around the tiger)

stanley kubrick shot his later films with a lens as fast as f/0.7 (a 25mm, i think), and it produced one of the most distinctive cinematic visual styles ever.

it's just a choice, and as long as you understand that relationship between aperature size and depth of field, and know what you want in focus and what you don't, you'll be alright.
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