My camera records something called "Hyperfocal Distance". I'm not sure what it is, but from that (and maybe with other parameters), can I calculate the actual focus distance? Or is that it, just with a different name?
Cheers
Alan
April 9, 2024
27
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photographylife.com/hyperfocal-distance-explained
From my understanding you couldn't because the hyperfocal distance is a function of focal length and aperture. You may have focused anywhere in or out of that range. But if you knew your focal distance, you can work out your acceptable depth of field, as fractions of H.
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Thanks.
Alan
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Alan, This is fairly readable yet pretty accurate. There are three concepts, the hyperlocal distance near (between the focal point and camera), the hyperlocal distance far (between the focal point and infinity) and the DOF which is their difference that go into calculating the hyperlocal distance.
www.waloszek.de/gen_dof_e.php#:~:text=exact%22%20aperture%20values.-,Calculating%20the%20Hyperfocal%20Distance,%2F(N*c)%20%2B%20f
What causes most of the confusion with digital cameras, other than "equivalence" is the circle of confusion. The circle of confusion, CoC or c in most equations is the size of a disk that the human cannot distinguish from a point. That is a property of human vision and it is different when viewing a print vs. 100% on a digital display. It varies with the distance at which the image is viewed. It is pretty simple of pixel peekers and is normally taken as 1.5 times the diameter of a pixel or the size a patch 3 pixels on a side viewed close to the display. However, viewing a 27 inch display at a more normally at two to three feet the CoC is larger. Viewed on a print in a gallery, it is larger still.
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That's interesting. It means that my Fuji X-T5's with a 40mp APS-C sensor has a smaller DoF than an X-T4's 26mp sensor because each photosite is smaller and therefore the CoC is smaller.
So, just saying it's APS-C sensor doesn't really help.
Alan
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( from Wikipedia )
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But the accepted (?) criteria for CoC is 3 pixels (a 9 pixel square). Which means the size varies depending in the pixel density.
Alan
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Yes if pixel peaked at 100% with your nose to the screen. No if viewed at a "normal viewing distance" of 1.5 times the diagonal of the image.
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If that is the accepted value of CoC, how come the commonly used DoF calculators (e.g. dofmaster.com) don't use the pixel density in their calculations?
I think most use the value 0.030mm for full-frame and scaled in proportion to the sensor diameter for other formats (e.g. 0.015mm for MFT). I like to think of that as CoC = image diameter/1500 (approx.).
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But isn't the essence of the excercise CoC is part of identical viewing conditions of the output?
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"The" Circle of Confusion is explained and discussed at great length by a well-known scientist here, leaving little room for further speculation in this dead thread:
kronometric.org/phot/iq/DepthOfField-Lyon.pdf
The hyperfocal distance is defined precisely and simply there, too ...
Like many things in photography, the CoC diameter is whatever Chuck Norris says it is ... ;-)
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Perhaps they are following the great photographic tradition of keeping it simple for the punters ...
... witness the well-worn subject of "ISO" as regards digital cameras.
For example, I have measured the "ISO" of the sensor in one of my digital cameras as 95 - no matter where I set the ISO knob.
In that camera, the sensor exposure in manual depends only on the shutter/aperture setting and incident light. All the ISO does is change the value of a digital multiplier used after writing the raw data to the card. Nice and simple ...
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SIMPLY???? Have you read it? I got about 5 pages in and my eyes went all funny 😁😂🤣
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Yes, I've read it and quoted it many, many times
OK, just "precisely" ...
Personally, I ignore the 'hyperfocal distance" and follow the recommendations of Merklinger ,,, well worth a read, I reckon, see:
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DOF is made much more complex by the insistence on calculating it in the image field (between the lens and sensor) rather than the object field (in front of the lens). All the geometry that defines DOF occurs in front of the lens. When you start to work in the image field you introduce all kinds of irrelevances, such as focal length, sensor size (in the object field you just have to consider angle of view), f-number (in the object field it is the aperture, the actual size of the hole through which the light is captured that matters) and a circle of confusion that changes as the sensor size changes (in the object field you need to think about the disc of confusion, expressed as a fraction of the angle of view). Texas Ted mentioned the Merklinger method, which is essentially derived using an object field method, though object field methods can be used to work out hyperfocal techniques too if you prefer those.
The difference between Merklinger and hyperfocal is essentially in the aims of calculating DOF. Hyperfocal centres about an absolute amount of out-of-focus blur that can be considered 'sharp enough', whilst Merkinger makes the 'sharp enough' criterion relative to objects in the scene. One example of the consequences is that Merkinger will generally render horizons much more sharply (visibly so) at the expense of a little more blur in the transition to the foreground. This makes it often a better choice for landscapes. -
Merlinger's emphasis on aperture diameter brings other benefits not just to do with DOF.
For example, his S = E/D*d where S = the disk of confusion at the OOF object; E = the OOF object position relative to the plane of focus; D = the distance to the plane of focus and d = the aperture diameter ... and shooting the moon:
What if you shoot the moon at f/22 and 1000mm lens but focus on a tree-line for effect say 4 km away, how will the moon look?
hint: diameter of the moon is about 3500 km and is about 400,000 km away.
d = 1000/22 = 45.4545 mm. D = 4km E = (400,000 - 4 km)
S = (400,000 - 4) / 4 * 45.4545 mm = 4545 km, which is 30% bigger than the moon. Therefore, the moon will appear that much larger in the image; less bright; and will be somewhat blurred.
If instead you focus on the moon, how will the trees look?
let the tree branches be 150 mm dia.
S = (400,000 - 4)/400,000 * 45.45 = 45.4540 mm which is 30% of the branch size. Therefore, the branches will be recognizable as such but rather blurred.
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Pixel count/size doesn't have anything to do with DOF, just as it doesn't have anything to do with diffraction blur. For example, if I took a photo of a scene using a A7R5 (61 MP FF) and A7S3 (12 MP FF) with the same settings and focal point, then displayed both photos at the same size, the DOFs would be identical.
However, sensor size does affect DOF. For example, a photo of a given scene taken from position with the same framing, focal point, and f-number, one with APS-C (1.5x) and the other with FF, displayed both photos at the same size, then the APS-C photo would have 1.5x as much.
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I find that the smaller the pixel-size, the greater the spatial sampling-rate - therefore the more resolved is the blur for a given aperture-diameter.
There is a phrase often used in lens reviews that diffraction "sets in" above some stated f-number, completely ignoring the effect of pixel-size on diffraction-visibility in the captured image.
