[BrianR]

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.

If it's the effect of cropping on DoF you'd like to see, I've posted this example before... DOF with FFs and APS-C - Page 5 - PentaxForums.com

[Na Horuk]

I already mentioned what the replies above tried to use as arguments. Equivalence only makes sense if you are trying to use one format to imitate another format. But why would you do that? Most photos never get printed, so canvas size and viewing distance are almost irrelevant. And why would I start my APSC workflow by imagining an FF image and then trying to make APSC DoF and bokeh equivalent to it? That is just silly. Nobody starts the image by deciding the exact distance of DoF they need. You can simply decide "more bokeh" or "hyperfocal" and so on.

That's why to me DoF is pretty straightforward and has mostly to do with focal length, focus distance, and aperture. You can take a photo of a measuring tape and check where the detail becomes sharp enough to be considered "in focus". Now, sure, things like pixel density, AA filter might affect this aspect, but generally speaking the crop of the sensor will not affect this. That's why I said to do a test with K-1 and switch modes, so that pixel density and sensor quality don't change, and neither would the lens, aperture, focus. And neither should PP sharpening, as it can also affect the illusion of sharpness.
And why are you guys saying DoF on APSC is more shallow? Wasn't a big argument why Pentax needs FF camera that people wanted more shallow DoF that only an FF camera can provide? IF you multiply the aperture by crop factor you would get wider DoF, not more shallow. I really don't get you guys.

But to stay on topic, regarding hyeperfocal: I recommend to OP to simply do a couple tests. This will eliminate all the issues and you can easily remember the focus distance for your lenses. Tests on your specific lens and camera are best, because sometimes a lens might be miscalibrated or the tolerance between lens and camera might be at odds. Sometimes what one person considers to be "sharp enough" is not good enough for another person's standards. So do some tests with your wide angle lenses at f5.6 and f8 and you will have a good idea what is hyperfocal on your gear. No need for equivalence or various DoF tools (which, for some reason, often give different results, depending on the app)

[BrianR]

And why are you guys saying DoF on APSC is more shallow? Wasn't a big argument why Pentax needs FF camera that people wanted more shallow DoF that only an FF camera can provide? IF you multiply the aperture by crop factor you would get wider DoF, not more shallow. I really don't get you guys..

Every time this comes up, and I mean every time, there are misunderstandings when someone tries to make simplified statements like "FF has less DoF than APS-C" or "APS-C has less DoF than FF". These statements are utterly and completely meaningless without stating the other assumptions involved. When you switch from a FF camera to an APS-C one do you:

-Stay at the same distance?
-Change lenses?
-Keep the framing of your subject the same?
-Change the aperture?
-Print (or view on screen) at the same size and distance?
-Change the visual acuity of the viewer (donning glasses or ingesting beer)?

These are some of the variables that matter when determining DoF, how these change (if at all) will influence which (if any) format ends up producing a photo with more DoF.

This has nothing to do with equivalence, and more to do with understanding what DoF is and how this fuzzy (haha) concept has been made precise and adopted to something useable (calculators, charts, etc.). It's important* to understand what the DoF tables depend on (which is why I linked to the more robust Cambridge in Colour calc., general DoF one here) so you can modify them to suit your specific use or demands.

Please, we've been here before... take a look at the example in the thread I linked to above and the long discussion if you want to rehash it.


*To clarify, I recognize that it's not going to be important to everyone, you can get along just fine and dandy with a basic understanding of what aperture, focal length, and subject distance do with regards to DoF. Take photo, adjust something to get it more like you want, and repeat. This is a fine way to operate if it's to your liking.

[stevebrot]

APS-C.



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

What he said ^ ^ ^. Since the capture is APS-C, use the APS-C calculation.

Final viewing size, distance, and visual acuity are assumptions built into the calculations* and all discussions regarding DOF should proceed with those assumptions understood. Unfortunately, the various calculators (online and apps) often yield different numbers. The same is true for the DOF scales on lenses and the convention suggested by the cambridgeincolor.com link above. The reasons are complicated.

Translation: There is no foolproof rule or calculation using DOF that will reliably assure acceptably sharp rendering for a specific distance range. What is "acceptable" is a fluid concept and unacceptable sharpness at infinity or near distance are more common than not.

Given the above, it should be obvious why the most common application of the hyperfocal distance has been in the design of snapshot cameras and for street photography. Use for near-far composition will generally result in disappointment and frustration. If one MUST have the BEST possible in-focus rendering for near-far composition, the options run like this:

• Adjust the plane of focus to reflect the composition using a view camera or similar setup -- or --
• Focus stacking in PP

One might also try focus bracketing around the calculated hyperfocal distance being aware that the eye is more forgiving of softness at distance than closeup.


Steve

* FWIW, I don't use calculated DOF for shooting except for street photography. I am fond of a phone app for rough comparisons and for feasibility stuff (https://play.google.com/store/apps/details?id=jds.dofcalc&hl=en).

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Last edited by stevebrot; 12-03-2017 at 01:36 PM.

[Alex645]

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

To answer the OP's question, for a FF in crop mode you should just calculate the hyperfocal distance for a FF camera and focal length. The question was NOT the affect on DOF.

If you go to DOFmaster.com, and compare a DOF table between a 50mm APS-C, you'll see the hyperfocal distance and DOF near/far ranges do not match a 75mm FF. So this implies that equivalence may work with FOV but not DOF. But if you look at the fine print on the bottom of the chart, they are defining the FF circle of confusion at a larger .03mm diameter, whereas the APS-C circle of confusion is defined as a smaller .02mm. In other words, we are not truly comparing apples to apples.

And +1 to Uncle Vanya: Just test it, evaluate it, and share it, because we can all have our theories but "the proof is in the pudding"; (tapioca or chocolate).

[stevebrot]

In case anyone is interested, a full discussion of the math and assumptions may be found in the Wikipedia article on Depth of Field:

Depth of field - Wikipedia

Even with all the math, I remember reading at some point that when all of the factors are zeroe'd out and accounted for, DOF depends on absolute magnification and entry pupil diameter and nothing more. That's right, no focal length, no format, no pixels.


Steve

[Ron Boggs]

I still have my old cheat charts with hyperfocal distances for each of my wide lenses at f22, f16 and f11. Carried a chart for 6x7 medium format and for 35mm. Hoped to find a similar chart for APS-C.

Apparently landscape work isn't popular anymore or is everybody stacking? (I typically stack macro but not landscape). Or is the depth of field in APS-C so deep that near/far landscape focus is now so easy to achieve no thought is necessary? Just drop the ap. to f16 and shoot? Note that getting both 13" away and 13 miles away in very crisp focus generally requires "dirty knee" work with tripod set very close to the ground.

I suspect that a very small percentage of shooters ever put themselves into a position requiring the critical focus control of hyperfocal distance. Thus the lack of discussion regarding field shooting in this thread. The razor thin dof with medium format really trained me to care--otherwise it didn't sell-- but with APS-C...ho hum...

Amazing how a simple question can degenerate into theoretical abyss!

[stevebrot]

If you go to DOFmaster.com, and compare a DOF table between a 50mm APS-C, you'll see the hyperfocal distance and DOF near/far ranges do not match a 75mm FF. So this implies that equivalence may work with FOV but not DOF. But if you look at the fine print on the bottom of the chart, they are defining the FF circle of confusion at a larger .03mm diameter, whereas the APS-C circle of confusion is defined as a smaller .02mm. In other words, we are not truly comparing apples to apples.

Hence, one of the problems with dofmasters-dot-com. I quit using them about a decade ago.

The OPs question was not one of equivalence of frame, but of hyperfocal distance. Solve the framing with focal length first and calculate the hyperfocal second. At least that is the conventional approach regardless of format.


Steve

[stevebrot]

Apparently landscape work isn't popular anymore or is everybody stacking?

Some do, but not too many that I know.

Or is the depth of field in APS-C so deep that near/far landscape focus is now so easy to achieve no thought is necessary?

Would be that were so!

Just drop the ap. to f16 and shoot? Note that getting both 13" away and 13 miles away in very crisp focus generally requires "dirty knee" work with tripod set very close to the ground.

Yep...guilty as charged, though f/22 is more common than f/16...diffraction be damned! Drop the aperture, focus near, and pray that the eye does not care that the mountains are not knife sharp.

The OP's question comes up about once a year on this site in one form or another. Near-far is the usual intent, though sometimes the purpose is a practical concern for street photography. I generally don't sweat infinity for street and opt instead for usable range out to about 20 meters.

The razor thin dof with medium format really trained me to care--otherwise it didn't sell-- but with APS-C...ho hum...

This is the best sentence of this thread. One does not get this sort of question in medium or large format forums. The struggle with DOF is palpable when the format gets big and those who shoot in that realm tend to not confuse the technical with technique.

Steve

[Ron Boggs]

This thread almost went all the way to "Circles of Confusion" discussion...whew...didn't need that...

Hey Steve, see you at Burgerville 134th St over Christmas season...grew up across the fields from there and still visit ma...have to hang the big telephoto out the window at Ridgefield refuge in winter...there's a different dof issue with the big 600/4.

[BrianR]

To answer the OP's question, for a FF in crop mode you should just calculate the hyperfocal distance for a FF camera and focal length. The question was NOT the affect on DOF.

If you go to DOFmaster.com, and compare a DOF table between a 50mm APS-C, you'll see the hyperfocal distance and DOF near/far ranges do not match a 75mm FF. So this implies that equivalence may work with FOV but not DOF.

Changing the sensor size (and nothing else) changes the hyperfocal distance. "Equivlance" does work for hyperfocal distance, you need to adjust the aperture just like you do for DoF (this is assuming you want them to match, it can't be said enough that matching images isn't the ultimate goal of equivalence, it's just a means of comparison).

Ex from your DoFmaster::

FF, 75mm and f/11, hyperfocal distance is 54.6ft.
APSC, 50mm and f/8, hyperfocal distance is 51.4 ft

They change the circle of confusion as they are assuming the same print size irregardless of format, so it's "apples to apples" if you're shooting with an intended print size (or screen size if you're an environmentally conscious paperless photographer).

Also see the calculator:

Understanding Your Camera’s Hyperfocal Distance

I still have my old cheat charts with hyperfocal distances for each of my wide lenses at f22, f16 and f11. Carried a chart for 6x7 medium format and for 35mm. Hoped to find a similar chart for APS-C.

Right here, any format you want, you can input your own focal lengths:

Understanding Your Camera’s Hyperfocal Distance

[Ron Boggs]

Oh, there they are...pretty little circles of confusion...

[photoptimist]

To answer the OP's question, for a FF in crop mode you should just calculate the hyperfocal distance for a FF camera and focal length. The question was NOT the affect on DOF.

If you go to DOFmaster.com, and compare a DOF table between a 50mm APS-C, you'll see the hyperfocal distance and DOF near/far ranges do not match a 75mm FF. So this implies that equivalence may work with FOV but not DOF. But if you look at the fine print on the bottom of the chart, they are defining the FF circle of confusion at a larger .03mm diameter, whereas the APS-C circle of confusion is defined as a smaller .02mm. In other words, we are not truly comparing apples to apples.

And +1 to Uncle Vanya: Just test it, evaluate it, and share it, because we can all have our theories but "the proof is in the pudding"; (tapioca or chocolate).

Equivalence isn't just about focal length, it's also a relationship in numerical aperture across formats to determine, for example, the aperture setting of 50mm APS-C that has the same image-level DoF properties as 75mm FF at some aperture.

And the FF circle of confusion of 0.03 mm vs. APS-C circle of confusion of 0.02 mm is required to create the apples-to-apples comparison at the image level (whether that means side-by-side prints or side-by-side images on a computer monitor or instagram). An FF image needs less magnification to view on a monitor or print vs. an APS-C image. Thus 0.02 mm of blur in an APS-C image on a monitor or print has the same size as a 0.03 mm blur in an FF image shown at the same output size.

But if the math is not convincing, then test it yourself.

[Ron Boggs]

Circles can be interesting...

[Alex645]

Changing the sensor size (and nothing else) changes the hyperfocal distance.

Yes, you are correct. I know this simply when I shoot 645 with a 75mm @f/2.8 and compare it to the same on FF 50mm or APS-C 35mm @f/2.8.

But again, the OP's question is with FF only and cropping the shot which can be done in camera or in post. That is not going to change the hyperfocal distance. It will affect (sorry for those of you allergic to this term) circles of confusion (or if you prefer the minimum diameter of a point of light that is accepted as sharp) as that cropped sensor or cropped image will now have a less resolution resulting in larger COC.

The other day I did a demo in class with a Nikon D750 and D7100 and below you will see:
1) FF 50mm f/1.4
2) FF 50mm f/1.4 cropped frame
3) APS-C 50mm f/1.4

Please try to ignore variation in the color balance and the APS-C is slightly forward focused. The questions:
Does the hyperfocal distance change from the uncropped vs. cropped FF? Does the DOF?
Should the OP use a chart for APS-C with 50mm in trying to determine the hyperfocal distance for FF cropped?

In my opinion to all three questions is 'no'.