Hyperfocal Scale on APS-C

godwinaustin · 01-25-2013, 10:07 AM

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?

Vasyl · 01-25-2013, 10:09 AM

No, you are not!

**boriscleto** · 01-25-2013, 10:20 AM

Originally posted by godwinaustin

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

godwinaustin · 01-25-2013, 10:21 AM

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?

godwinaustin · 01-25-2013, 10:28 AM

Originally posted by boriscleto

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.

**Just1MoreDave** · 01-25-2013, 10:46 AM

Originally posted by godwinaustin

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.

JohnX · 01-25-2013, 10:50 AM

I use an app on my smartphone that takes crop factor into account.

godwinaustin · 01-25-2013, 11:03 AM

Originally posted by JohnX

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.

Na Horuk · 01-25-2013, 11:31 AM

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"

JinDesu · 01-25-2013, 11:36 AM

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.

godwinaustin · 01-25-2013, 11:38 AM

Originally posted by JinDesu

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

JinDesu · 01-25-2013, 11:42 AM

Originally posted by JohnX

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?

**THoog** · 01-25-2013, 12:00 PM

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.

mdodrill · 01-25-2013, 12:19 PM

Originally posted by boriscleto

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)

vonBaloney · 01-25-2013, 12:43 PM - **1 Like**

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...

01-25-2013, 10:07 AM	#1
godwinaustin Forum Member Join Date: Dec 2012 Location: Jackson, Wyoming Posts: 89	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?

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01-25-2013, 10:09 AM	#2
Vasyl Veteran Member Join Date: Aug 2010 Photos: Gallery Posts: 648	No, you are not!

01-25-2013, 10:20 AM	#3
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Originally posted by godwinaustin 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
godwinaustin Forum Member Join Date: Dec 2012 Location: Jackson, Wyoming Posts: 89 Original Poster	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
godwinaustin Forum Member Join Date: Dec 2012 Location: Jackson, Wyoming Posts: 89 Original Poster	Originally posted by boriscleto 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
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	Originally posted by godwinaustin 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
JohnX Pentaxian Join Date: Jul 2009 Location: London Posts: 1,116	I use an app on my smartphone that takes crop factor into account.

01-25-2013, 11:03 AM	#8
godwinaustin Forum Member Join Date: Dec 2012 Location: Jackson, Wyoming Posts: 89 Original Poster	Originally posted by JohnX 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
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	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
JinDesu Veteran Member Join Date: Jun 2011 Location: New York City Photos: Gallery Posts: 5,638	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
godwinaustin Forum Member Join Date: Dec 2012 Location: Jackson, Wyoming Posts: 89 Original Poster	Originally posted by JinDesu 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
JinDesu Veteran Member Join Date: Jun 2011 Location: New York City Photos: Gallery Posts: 5,638	Originally posted by JohnX 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
THoog Loyal Site Supporter Join Date: Aug 2012 Location: North Carolina Photos: Gallery \| Albums Posts: 3,685	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
mdodrill Senior Member Join Date: Dec 2011 Location: Ohio Posts: 231	Originally posted by boriscleto 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
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	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...