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Hyperfocal Distance


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6 replies to this topic

#1
ScottinPollock

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So while I fully understand the concept, and have used it to a certain extent, I have never counted on it, mostly because I have not taken the time to experiment.

My concern is what is supposed to be in focus. For any given sensor, focal length, aperture, and focus point, how "in focus" will everything be within the calculated DOF? "Tack Sharp" or some definition of "acceptable".

#2
dcbear78

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I used this when using my manual focus fish eye lens. Was just easier to set it at something like f16+ and minimum focus distance and everything was in focus.

I still use it for my landscape work. Especially if there isn't something very specific I want focus on.

#3
Merco_61

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If the CoC is chosen correctly for the reproduction scale and the intended viewing distance, the eye will not be able to see the difference in sharpness within the DOF. This means that you will have to think about how the finished print will be presented to use it efficiently. The DOF will of course not be pixelpeeping sharp over the whole range, but that doesn't matter if the intention is a photograph and not a specimen for dissection.



#4
leighgion

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Definitely not "tack sharp." You're looking "some degree of acceptable," which in many, possibly even most, cases is more than good enough for the majority of shooters.

If you want to get technical, even normal focus scenarios only ever have a single plane in actual focus and the rest is just "acceptable" to our eyes.


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#5
dcbear78

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Don't know... This seems pretty sharp to me? This was done using hyperfocal distance because I wanted as much of the scene in focus as possible.

1e6e05f5bc50abdb143aafe580423de4.jpg

#6
dem

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What is "acceptable" mainly depends on the size you are going to display your images and the distance you are going to view them from.

 

Theoretically speaking the only thing which is in focus is the focus plane. Any point that is slightly behind or in front of the focus plane is going to be projected as a small circle on the sensor. If the size of this circle is smaller than the size of a pixel, you would probably describe this as being "tack sharp" as there will be little blur visible even at 100% magnification on the screen.

 

Now print this image 8"x10" and view it from a normal reading distance. Your eye won't be able to tell the difference between 12 Mp and 36 Mp image even if you printed them using a 1200 dpi printer that costs more than a family car. From this distance human eye can resolve only about 5 lines per mm and this is what is taken into account in DOF calculators that all use CoC - circle of confusion, mentioned by Peter. But then if you have a close look, it will be obvious which image came from a 36 Mpx sensor.

 

Note that this is simple geometric optics and has nothing to do with diffraction, Airy discs etc...



#7
KevinButle

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This question rarely comes up, as TCs are typically not used with wide-angle lenses, and the hyperfocal distances for long focal lengths are pretty large. For example with a 200mm lens on a DX-format sensor at f/16, using HF focussing you might be able to get 60m-infinity in focus. But 60m is still a fair way away I think youll find that with a 2x TC you would feed 2x the focal length into your calculator, along with 2x the aperture. About the only thing that DOES stay the same with a TC is the lenss focus distance i.e. the minimum focus distance stays the same.