The 80/1.7 GF on the GFX 100S has *more* DOF than calculators say

Started 2 months ago | Discussions thread
Erik Kaffehr
Erik Kaffehr Veteran Member • Posts: 5,844
Re: The 80/1.7 GF on the GFX 100S has *more* DOF than calculators say

JimKasson wrote:

Hamiltionian wrote:

JimKasson wrote:

Not much more, but more, at least at f/2 and subject distances of 101 and 55 meters:

https://blog.kasson.com/the-last-word/are-dof-calculators-useful/

And the DOF is slightly asymmetrical, to boot.

Jim

"""If we focus on the front tree and look at the back tree, we should see the same amount of blur that we see if we focus on the back tree and look at the front tree.''''

True as long as f << S1, where S1 is the distance to the focal plane in the objects space, and definitely true in this case.

Right.

Spherical aberration is much more likely the source of the asymmetry. Especially since this is designed as a portrait lens and such an asymmetry is a feature.

I would agree that SA is the most likely suspect. What is interesting to me is that the asymmetry is slight, at least at these largish blur circles.

I would agree on SA, but must say, I don't have any ponies in this race.

I would think that the DoF concept is good for understanding the concept of in and out of focus rendition. Also, I would suggest that it is good that DoF-tools are decent predictor for transition between in focus and out focus.

But, all that stuff has been known for like 100 years, so it doesn't come as a great surprise.
I would say that DoF calculators may be useful, if we have the knowledge to use them correctly.

Best regards

Erik

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Erik Kaffehr
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