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12-12-2008, 02:00 PM   #16
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Thanks everybody

12-12-2008, 02:22 PM   #17
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Most of the comments are pretty informative generalizations on a very complicated subject. As a general suggestion to the OP:
  • Look at the other threads dealing with this topic on this forum. They are quite large and rather contentious, but contain a lot of information.
  • Check out the Wikipedia article on Depth of Field. It is technical, but has informative nuggets if you are interested.
  • Play with the various Depth of Field Calculators on the Web. The better ones allow you to change most of the factors used for DOF calculation. One of my favorites is Julian's Lens Calculator. (Julian's layout is a bit of a mess and it is not very intuitive, but at least it is complete.)

As a final comment from me...It is important to note that depth of field is the range of acceptable apparent sharpness. While the calculations are rooted in physics, the constants are based on human perception. In reality only one point in the DOF range is actually in focus. The rest is only "acceptably" so.

Steve

(Wasted many, too many hours thinking about and discussing this topic...)

Last edited by stevebrot; 12-12-2008 at 05:46 PM. Reason: Edited to be more friendly and informative...:)
12-12-2008, 02:24 PM   #18
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QuoteOriginally posted by Gooshin Quote
Gooshin does ART!!

Excellent drawing.

Steve
12-12-2008, 04:15 PM   #19
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Geez Stevebrot, the OP was actually quite a bit different than the tired old--what's an f stop? or what does dof mean? I bet Wikipedia doesn't make a whole lot of distinction between medium format dof and FF dof which were both part of his question. Plus we all read it because the OP used the modern trap "FF" to get us to peek...I'm giving the OP extra permission this time because his dof question wasn't the same old tired question.
Hell, if the OP was advertising, he did well. Not only did all of us look at it, several of us acted on it and responded.

12-12-2008, 05:04 PM   #20
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QuoteOriginally posted by Gooshin Quote
the black indicates you not moving anywhere while changing formats, but not lenses, and the resultant change in field of view, but same DOF
Either I'm missing something in your assumptions here or you are. Depth of field depends just as much on the apparent size of the viewed final image as anything else.

If you take pictures on different formats with the same lens, the actual circles of confusion on the sensor or film medium will be identical.

But in order to reproduce the picture for viewing at a given size (say, a print or on-screen display that's 10 inches wide) you'll have to enlarge the image from the smaller sensor more. This means the circles of confusion will be larger and hence the depth of field smaller. This is alluded to by Georg's post above describing the differences in maximum circle of confusion size for FF vs. APS-C.
12-12-2008, 05:37 PM   #21
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QuoteOriginally posted by Ron Boggs Quote
Geez Stevebrot, the OP was actually quite a bit different than the tired old--what's an f stop? or what does dof mean? I bet Wikipedia doesn't make a whole lot of distinction between medium format dof and FF dof which were both part of his question. Plus we all read it because the OP used the modern trap "FF" to get us to peek...I'm giving the OP extra permission this time because his dof question wasn't the same old tired question.
Hell, if the OP was advertising, he did well. Not only did all of us look at it, several of us acted on it and responded.
Thanks for the jolt. Re-reading my comment, it does seem a bit abrupt.

No offense meant to the OP. The main issue is that there is a lot of misinformation regarding this subject and every time it comes up, the same stuff goes around. The main problem is that the whole subject of DOF is a lot more involved than it first appears. As has been noted in many of the posts, the dependencies include:
  • Aperture
  • Circle of confusion (aptly named)
  • Magnification at the focal plane
  • Final viewing size
  • Final viewing distance
  • Assumptions of "normal" visual acuity for the eventual viewer
Did I list them all? (Probably not...)

I will edit my comment to be a little friendlier and exit this thread gracefully (I hope)

Steve

(Thinking as he leaves...that is why DOF preview is so important...)
12-13-2008, 11:09 AM   #22
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No worries Stevebrot...and if it is now snowing even at your low elev. (I grew up there and visit often) the Ridgefield Refuge offers some decent "in town" shooting--if it isn't closed for hunting today--lowland oaks, coyote tracks in the snow, mink that are somewhat tame, tree shrouded dirt roads. I often go to Ridgefield when it snows...it's definitely more fun than this thread!
12-13-2008, 03:06 PM   #23
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QuoteOriginally posted by Ron Boggs Quote
No worries Stevebrot...and if it is now snowing even at your low elev. (I grew up there and visit often) the Ridgefield Refuge offers some decent "in town" shooting--if it isn't closed for hunting today--lowland oaks, coyote tracks in the snow, mink that are somewhat tame, tree shrouded dirt roads. I often go to Ridgefield when it snows...it's definitely more fun than this thread!
Nope, no snow yet. The white stuff is supposed to arrive tomorrow. I have never been to the Ridgefield Refuge in the snow, though I can image that it is pretty cool. I shoot there every once in a while and have posted a few shots on this site. The main problem with Ridgefield is that the south unit is closed to foot travel in the winter except for hunters and the north unit is mostly underwater. (I have been known to sneak into the south unit from the River Road side, though I always feel sort of guilty when I do.)

Steve

(We now return this thread to its previous on-topic discussion...)

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