New to MF - have a few ?'s

Discussion in 'Medium Format & Large Format' started by SamHodde, Feb 6, 2017.

  1. compur

    compur No longer a newbie, moving up!

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    No, that's not what it says. Read it again.

    Same focal length plus same enlargement = same DOF for different formats.


     
  2. Ysarex

    Ysarex Been spending a lot of time on here!

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    And that is saying the very same thing -- that's what "same enlargement" means. "Same enlargement" means you crop out the equivalent area of the larger format and enlarge it to the same degree as the smaller format.

    You first said; "DOF is determined by lens focal length and aperture regardless of film format." That's incorrect. Folks who shoot medium format cameras don't process their film and then only make prints enlarged to the same degree as if they had shot 35mm film. They don't take a pair of scissors and cut out 35mm sections from their 120 negs to print from.

    Joe

    P.S. From the same Wikipedia article: "When the "same picture" is taken in two different format sizes from the same distance at the same f-number with lenses that give the same angle of view, and the final images (e.g., in prints, or on a projection screen or electronic display) are the same size, DOF is, to a first approximation, inversely proportional to format size (Stroebel 1976, 139)."
     
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  3. Derrel

    Derrel Mr. Rain Cloud

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    The idea of the same picture made at the same f-stop but using larger or smaller camera formats explains the practical everyday reality of depth of field. Anybody who has used medium format roll film will tell you there is a need to close the lens down at least two f-stops smaller than what one would use for the same type of clothes in pictures made on a 35 millimeter camera. Anybody who has used an iPhone will tell you that the depth of field is almost incredibly deep at 5 feet at any lens aperture.

    As far as Split Image Rangefinder focusing goes this system is very accurate with a skilled operator in a properly calibrated camera, but neither of those two are a given in every situation. Medium format cameras like the Mamiya are great for slow shooting and careful placement of the focus point and the depth of field band. It's not too surprising that your first efforts with the new camera did not produce the kind of fast,easy results you're used to with digital systems. The Mamiya was never intended to be a fast, fluid, carefree camera, but was designed for a very disciplined, practiced type of shooting. As I mentioned earlier, at closer distances, medium format cameras do not deliver the type of depth of field or the fast and easy Focusing that many people are used to with modern digital cameras.
     
  4. compur

    compur No longer a newbie, moving up!

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    I fully agree that in the real world one usually gets less DOF shooting MF vs 35mm and I said so in my first post.

    I also said that the same focal length and same enlargement results in the same DOF and gave a reference to back up that statement.

    I don't know what the big argument is about. If one disagrees with my reference then complain to the wikipedia. It says what it says and I didn't write it.

    No, it isn't as long as the degree of enlargement is the same and I gave a reference to back that up.

    Maybe you are confused by "same degree of enlargement"? It just means if you enlarge by say 4:1 then you'd get a 4x6 print from a 35mm negative or roughly a 9x11 (8x10 in the real world) print from a 6x7cm negative. I don't think either of these print sizes are unusual or "not what folks who shoot medium format do." I have made many 4x6 prints from 35mm negatives and many 8x10s and 11x14s from 6x7 negatives. What is so "not-real-world" about making prints in these sizes?
     
  5. Ysarex

    Ysarex Been spending a lot of time on here!

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    And you went on to qualify that statement in that same sentence: "However medium format cameras do tend to use longer lenses than 35mm cameras so in that sense you will tend to have shallower DOF with a MF camera but it's not the film format that is causing it." The film format is in part causing a DOF difference and you could possibly slide by with this statement except that you said in the previous sentence: "DOF is determined by lens focal length and aperture regardless of film format." That's wrong. Film format is a DOF determinant factor. You're first post is incorrect -- obviously proven so by the illustrations I posted.

    No you did not. You're use of "also" in this sentence is a trumpian attempt to imply you said that in your first post. Here's your entire first post:

    "DOF is determined by lens focal length and aperture regardless of film format. However medium format cameras do tend to use longer lenses than 35mm cameras so in that sense you will tend to have shallower DOF with a MF camera but it's not the film format that is causing it. In other words, if focal length and aperture are the same on a 35mm vs MF camera then the DOF will also be the same with both."

    There is no mention in your first post of enlargement. In fact your 3rd and final sentence drives home the initial error. If focal length and aperture are the same on a 35mm vs MF camera the DOF will NOT be the same with both. You mentioned enlargement in your 2nd post after I pointed out your first post was incorrect. Your first post still stands as incorrect and the condition of "same enlargement" is simply a way of removing the variation of format size from the equation and is completely lame.

    If you're going to do a comparison of DOF between cameras with different formats the only valid comparison that makes sense is to take the same photo with both. That will necessitate different degrees of enlargement (which is also pointed out in the Wiki article you referenced) and the difference in DOF that will occur will be in part due to the difference in the film formats.

    Joe
     
  6. compur

    compur No longer a newbie, moving up!

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    This has just gotten too ridiculous to continue. I advise others, if they are interested, to simply read the wikipedia page on Depth of Field which I happen to agree with but don't really care enough to argue about.

    Joe, you may now carry on enlightening the world with your superior knowledge of all things photographic without further interruption from me.
     
  7. Ysarex

    Ysarex Been spending a lot of time on here!

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    No argument from me over the Wiki article -- good source.

    Joe

     

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