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12-03-2017, 08:36 AM   #1
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Hyperfocal distance in APSC mode?

For KI in APSC mode should you calculate hyperfocal distance for a FF camera or an APSC equivalent?

12-03-2017, 08:50 AM - 1 Like   #2
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You should use a aps-c determined hyperfocal distance. This is because you are capturing your image on an aps-c sized portion of the sensor.
12-03-2017, 09:20 AM   #3
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Or is the camera just cropping the full frame image?
12-03-2017, 09:28 AM   #4
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QuoteOriginally posted by R. Glasgow Quote
Or is the camera just cropping the full frame image?
If the camera was doing that, the same rules would apply. But it is not, the k1 in crop mode just uses a 15mp cropped portion of the sensor.

You can see this in action when you switch to crop mode. In the viewfinder a thick black frame appears showing you the crop that you must keep your subject within. In Live View mode the crop portion of the image gets enlarged showing you exactly what the cropped portion of the sensor is seeing.

12-03-2017, 09:38 AM   #5
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QuoteOriginally posted by R. Glasgow Quote
For KI in APSC mode should you calculate hyperfocal distance for a FF camera or an APSC equivalent?
APS-C.

QuoteOriginally posted by R. Glasgow Quote
Or is the camera just cropping the full frame image?
Yes, it's just cropping the FF image down to the central APS-C sized portion.

Inherent in any of these DoF calculators is the size of the end image which is assumed to be constant, typically 8x10" (viewing distance and visual acuity are also assumed constant). When you crop from FF down to APS-C and then view at the same print size from the same distance DoF changes - you're magnifying it more so everything gets a bit more blurry.

See the calculator below, click on "show advanced":

Understanding Your Camera’s Hyperfocal Distance
12-03-2017, 09:38 AM - 1 Like   #6
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QuoteOriginally posted by R. Glasgow Quote
Or is the camera just cropping the full frame image?
It does not matter.

The visual perception of focus in the final image only depends on the pixels used for the final image. A K-5 (APS-C camera), a K-1 in APS-C mode, or a K-1 in FF mode but cropped to APS-C in post will all have the same hyperfocal distance (which is different from the K-1 in FF mode with no cropping in post).

The viewer of the print or image is not influenced by any of the pixels that were never there or were discarded by cropping.
12-03-2017, 09:45 AM - 1 Like   #7
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QuoteOriginally posted by R. Glasgow Quote
Or is the camera just cropping the full frame image?
just to be clear, when you say "is the camera cropping the full frame image", what it is NOT doing is capturing an image on the Full Frame sensor and resizing it.
12-03-2017, 09:48 AM - 1 Like   #8
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QuoteOriginally posted by R. Glasgow Quote
For KI in APSC mode should you calculate hyperfocal distance for a FF camera or an APSC equivalent?
If you focus your lens at a certain distance and use a specific aperture, it will give you a certain DoF, from one distance to another. This distance will not change if you switch to APSC mode. It will be the exact same image, except with the edges cut off. The sensor size can not change the image that the lens renders, it can only capture more or less of it, at a higher or lower resolution.

Equivalence is only important when you are trying to imitate one format when using another format. But this is ultimately futile and silly. Use what you have to the best that you can


Last edited by Na Horuk; 12-03-2017 at 09:53 AM.
12-03-2017, 09:52 AM - 1 Like   #9
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QuoteOriginally posted by Na Horuk Quote
If you focus your lens at a certain distance and use a specific aperture, it will give you a certain DoF, from one distance to another. This distance will not change if you switch to APSC mode. It will be the exact same image, except with the edges cut off. The sensor size can not change the image that the lens renders, it can only capture more or less of it, at a higher or lower resolution.
Sorry that is just plain wrong. You are ignoring what has to be done to the captured image in order to produce the same sized picture (on screen or in print) It is this "enlargement" (actually less reduction), which changes the DOF and hyperfocal distance.

See the other replies above. If your logic was correct Medium and Large format cameras would never have left the camera shops shelves
12-03-2017, 09:56 AM   #10
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QuoteOriginally posted by pschlute Quote
Sorry that is just plain wrong. You are ignoring what has to be done to the captured image in order to produce the same sized picture (on screen or in print) It is this "enlargement" (actually less reduction), which changes the DOF and hyperfocal distance.
Ok, put a prime on your K-1, focus and take a photo. Switch to APSC mode, take a photo. Does the APSC photo have wider DoF than the FF photo? No. Did the focus change? No. It just has edges cut off. This makes the illusion that DoF and bokeh are different in the overall photo, especially if you would print both photos into the same sized canvas. And that is what I meant by trying to imitate another format. If you want to make an APSC photo printed on A4 look the same as an FF photo printed on A4, then you need to use different settings (aperture, focal length,..). But why would anyone ever do that? Its a pointless comparison to make. Equivalence was only sensible back when APSC was just invented and everyone was used to 35mm film. Today, it only confuses new photographers.
12-03-2017, 10:11 AM - 1 Like   #11
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QuoteOriginally posted by Na Horuk Quote
Ok, put a prime on your K-1, focus and take a photo. Switch to APSC mode, take a photo. Does the APSC photo have wider DoF than the FF photo? No.
Assuming you haven't changed the lens, focal distance, aperture, or print size, viewing distance, etc. the dof will be smaller on the APS-C image than the FF image.

DoF is used to measure the blurriness of the final image, the thing we are hanging on the wall and looking at. It's not an illusion, it's how DoF is defined and unless we're interested in capturing and looking at the unprocessed data stored in an image file, it's the most sensible view imo.

You're trying to assign DoF to the thing you'd see in the image plane, that's not how the term has been traditionally used as far as I know.
12-03-2017, 10:13 AM   #12
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QuoteOriginally posted by Na Horuk Quote
Ok, put a prime on your K-1, focus and take a photo. Switch to APSC mode, take a photo. Does the APSC photo have wider DoF than the FF photo?
The aps-c picture will have a narrower DOF. This is because when I print the two pictures or view them on screen, the FF has 36mp to start off with and the aps-c one has only 15. Less resolution means less DOF.

---------- Post added 12-03-17 at 05:18 PM ----------

QuoteOriginally posted by BrianR Quote
You're trying to assign DoF to the thing you'd see in the image plane, that's not how the term has been traditionally used as far as I know.
Correct. DOF has always been measured by what the eye can see at a certain viewing distance when looking at a certain sized print.
12-03-2017, 10:20 AM - 1 Like   #13
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QuoteOriginally posted by pschlute Quote
The aps-c picture will have a narrower DOF. This is because when I print the two pictures or view them on screen, the FF has 36mp to start off with and the aps-c one has only 15. Less resolution means less DOF.
DoF measures the blur discs, not the resolution. Cropping, then printing at the same size enlarges these discs (note this is different than just cropping with scissors).

Edit- maybe you're equating the resolution drop with the crop. To clarify, a k5 (16mp aps-c) and a k3 (24mp aps-c) produce images with the same DoF (assuming same lens, distance, etc)

Last edited by BrianR; 12-03-2017 at 10:26 AM.
12-03-2017, 10:39 AM - 2 Likes   #14
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QuoteOriginally posted by Na Horuk Quote
Ok, put a prime on your K-1, focus and take a photo. Switch to APSC mode, take a photo. Does the APSC photo have wider DoF than the FF photo? No. Did the focus change? No. It just has edges cut off. This makes the illusion that DoF and bokeh are different in the overall photo, especially if you would print both photos into the same sized canvas. And that is what I meant by trying to imitate another format. If you want to make an APSC photo printed on A4 look the same as an FF photo printed on A4, then you need to use different settings (aperture, focal length,..). But why would anyone ever do that? Its a pointless comparison to make. Equivalence was only sensible back when APSC was just invented and everyone was used to 35mm film. Today, it only confuses new photographers.
Equivalence is not nonsense. It is a crucial part of learning to make photographs rather than merely take photographs.

If someone wants to make a photograph with a certain look such as a head-shot portrait with extremely strong blurring of the background, or night city scape with bokeh circles of a certain relative size, or a landscape with both in-focus foreground flowers and in-focus background, then they need to learn how their camera's format influences DoF at the frame height level (not the pixel-peeper level).

Equivalence will be an essential (if very advanced topic) in photography as long as photographers use a wide range of formats (from smartphones to large format) and other photographers seek to use their chosen format to make a photograph with the same specific amount of DoF that they see in another person's work using a different format.
12-03-2017, 11:28 AM - 4 Likes   #15
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For crying out loud. Rather than tell each other the other is wrong - just take some shots - and post them. FF and APSC same lens and show with PICTURES what happens.
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