DoF may not exist...

Started 3 months ago | Discussions thread
highdesertmesa
highdesertmesa Contributing Member • Posts: 716
Re: It is Science and Perception

JimKasson wrote:

DMillier wrote:

I suspect expectation plays a part.

You have pixel peeped so many ultra sharp GFX shots now, that maybe your brain can't accept even the most conservative CoC values.

I gave Greg a test to perform to see if using a conservative CoC worked. That was a year ago. He has not performed it. So we don’t know if a conservative CoC fits with his perception. It would be a useful experiment, and would probably go a long way towards getting to the bottom of this.

Would you mind re-posting the link to that or start a new thread with that test? I currently am without a GFX, but I'd be interested to try it on a smaller format.

–/–

Something I've encountered on the rare occasions I do need a lot of DOF that can be frustrating:

Under these conditions:

  • Shooting vertically
  • 135 format
  • FOV = wide angles =>21

I get this:

  • Acceptable DOF often falls off very near to the bottom edge of the frame. That by itself is not unusual, but –>

With this frustration:

  • It may take more than one stop to "push through" that final 0.5m of distance to get the entire foreground in focus.

So my question would be, which of these (all/any/none) is at work:

  • Focused distance was too far away / too much emphasis was given to infinity sharpness
  • Lens used does not have enough field curvature to favor the distances involved
  • Focus falloff from the area of acceptable DOF is not linear

I think the last bullet is the question I'm most interested in – Focus falloff from the CoC – is it always linear or does it ramp up on a curve toward the closest distance in the frame? If it is not linear, is it always the same or is it influenced by lens design?

Below is an example on the M10M with CV 21 1.4. My horizontal shot easily has enough DOF at f/5.6, but the vertical version I just left at f/5.6, too, since it took f/16 to cover that last 0.2m of the scene (f/8 was almost no difference from f/5.6). I could have moved the point of focus closer, but I didn't want to sacrifice infinity performance, but perhaps that is the sacrifice I should have made given the importance of the foreground versus the background in the vertical shot. Of course, two shots focus stacked at f/5.6 would have been the best solution.

Ignore the aperture in the EXIF – Leica M cameras/lenses do not have an electronic connection to the lens, and aperture is estimated by the camera (and rather poorly at times).

Apologies for the slight Dutch Angle, but compositionally it didn't look as good with the horizon perfectly leveled.

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