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01-25-2013, 10:07 AM   #1
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Hyperfocal Scale on APS-C

Am I right in believing that the hyperfocal distance scale on manual focus lenses is not accurate on my shiny new K30 because of the crop sensor?

01-25-2013, 10:09 AM   #2
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No, you are not!
01-25-2013, 10:20 AM   #3
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QuoteOriginally posted by godwinaustin Quote
Am I right in believing that the hyperfocal distance scale on manual focus lenses is not accurate on my shiny new K30 because of the crop sensor?
You have to adjust the f-stop by the crop factor. So instead of f/8 use f/12.

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/136792-q-about-...ml#post1427833
01-25-2013, 10:21 AM   #4
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really? I thought because of the crop sensor depth of field is different than 35mm film and/or full frame. so the hyperfocal distance range on the lens is totally accurate?

01-25-2013, 10:28 AM   #5
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QuoteOriginally posted by boriscleto Quote
You have to adjust the f-stop by the crop factor. So instead of f/8 use f/12.

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/136792-q-about-...ml#post1427833
so basically it is kind of useless, but not totally useless.

so in summary: for MF on aps-c using the hyperfocal scale, stop down 1 or 2 stops from F/ number on the distancing scale for proper DOF.
01-25-2013, 10:46 AM   #6
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QuoteOriginally posted by godwinaustin Quote
so basically it is kind of useless, but not totally useless.
Well, just look at most distance scales - not linear, not a lot of points marked. Then your own ability to judge distances. Now you're in a real world situation, probably not at one of the marked distances away from the subject, and have to use those combined to focus. I think one stop off is often well within the margin of error from the other factors.
01-25-2013, 10:50 AM   #7
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I use an app on my smartphone that takes crop factor into account.
01-25-2013, 11:03 AM   #8
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QuoteOriginally posted by JohnX Quote
I use an app on my smartphone that takes crop factor into account.
me too, its nice to be able to use the distance scale though - even if it is a bit rough around the edges.

01-25-2013, 11:31 AM   #9
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The DoF doesn't depend on the sensor size, but APS-C sensors usually have a higher pixel density and will therefore show the same image as "not as sharp"
Keep in mind that hyperfocal was never "perfect sharpness," but just "acceptable sharpness"
01-25-2013, 11:36 AM   #10
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Why do we stop down more on APS-C? If my hyperfocal says everything from 20' to infinity is in focus, wouldn't my 1.5x crop just show even less of the foreground?

I always thought the statement was - at the same aperture, full frame/35mm has thinner DOF than APS-C, because the crop enlarges the DOF.
01-25-2013, 11:38 AM   #11
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QuoteOriginally posted by JinDesu Quote
Why do we stop down more on APS-C? If my hyperfocal says everything from 20' to infinity is in focus, wouldn't my 1.5x crop just show even less of the foreground?

I always thought the statement was - at the same aperture, full frame/35mm has thinner DOF than APS-C, because the crop enlarges the DOF.
this is what I thought too
01-25-2013, 11:42 AM   #12
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QuoteOriginally posted by JohnX Quote
I use an app on my smartphone that takes crop factor into account.
In reviewing my smartphone's app, it says that with the same lens and aperture and focal distance, the APS-C will have thinner DOF... perhaps I was thinking it wrong?
01-25-2013, 12:00 PM   #13
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This is what I do with my M lenses - line up the orange numbers, then turn to the right one mark. I've verified the numbers with a couple hyperfocal calculators and with some test shots. It works for the 28mm and 35mm lenses I've tried. It may not work for other lenses/apertures, but if f/8 was good enough for Pentax in the 80s, it's good enough for me.


01-25-2013, 12:19 PM   #14
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QuoteOriginally posted by boriscleto Quote
You have to adjust the f-stop by the crop factor. So instead of f/8 use f/12.

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/136792-q-about-...ml#post1427833
You have me confused now: I am new to digital photo but thought a 21 mm lens on my pentax k-r was equal to a 35mm angle of view (on a film or ff DSLR) but that f16 on a 21mm lens gives the same hyperfocal no matter what type of camera (APS or FF)
01-25-2013, 12:43 PM - 1 Like   #15
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More victims of the equivalency brigade I see. Na Horuk has it basically correct. The image is just cropped compared to a full-frame -- that's it. However, that means you'll be likely enlarging it more for display than you would if you were using that same lens on a full-frame, and so the crop sensor is "stressing" the lens more if you will. So it makes sense to fudge the scale over so that the boundaries of "acceptable sharpness" are more stringent when using a crop sensor. So when using the same lens with the same aperture, the crop sensor does essentially give you THINNER DoF than a full-frame. It is only when we get into "equivalent" lenses (which means different focal length lenses) on different format bodies that the larger format allows thinner DoF.

But anyway, the DoF scales printed on old lenses are assuming full-frame, and you will find it wise to use a tighter boundary with your crop sensor by fudging it by a stop or so...
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