DOF calculation for Hasselblad X system sensors

[tobiasash]

I just wanted to see if anyone has identified or uses an online or app based DOF calculator that has the dimensions of the Hasselblad X system sensor built in.
Currently, I am using one that I need to manually convert the focal length and f stop by the .79 crop factor. In most situations this works well, however when I am trying to calculate the step size when focus stacking images with longer focal lengths and maximum apertures, I find that the relative 35mm aperture that I have used is not accurate and I am having to repeat the focus stack again.

I hope that makes sense. Any tips or suggestions is much appreciated.

(edit) I have included a practice stack from yesterday. I initially set the stack for extra small and took 30 photos. This only covered the front of the leaf. Then changing to small steps with 30 photos but now there are bands that aren't in focus where it has jumped too much.

 

[MGrayson]

DoF depends on many variables. I would simply experiment. Start with a large step between two images and stack them. You should be able to see a soft region in between the sharp ones. Decrease the step size until you can't see softness for your intended application. I often find that I don't use every shot in the stack, preferring to make only certain portions of the image sharp and leaving the others indistinct.

As much as I love mathematical optics, I'd ignore the formulas in this case.

 

[rdeloe]

I just wanted to see if anyone has identified or uses an online or app based DOF calculator that has the dimensions of the Hasselblad X system sensor built in.
Currently, I am using one that I need to manually convert the focal length and f stop by the .79 crop factor. In most situations this works well, however when I am trying to calculate the step size when focus stacking images with longer focal lengths and maximum apertures, I find that the relative 35mm aperture that I have used is not accurate and I am having to repeat the focus stack again.

I hope that makes sense. Any tips or suggestions is much appreciated.

This online tool has Hasselblad X in the list of sensor/film sizes: https://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator

 

[tobiasash]

DoF depends on many variables. I would simply experiment. Start with a large step between two images and stack them. You should be able to see a soft region in between the sharp ones. Decrease the step size until you can't see softness for your intended application. I often find that I don't use every shot in the stack, preferring to make only certain portions of the image sharp and leaving the others indistinct.

As much as I love mathematical optics, I'd ignore the formulas in this case.

Excellent advice. Thankyou. I guess I was trying to speed up the process but that makes perfect sense.
I also am going to experiment with stopping down a little to see if this takes care of it as well.
I have included a practice stack from yesterday. I initially set the stack for extra small and took 30 photos. This only covered the front of the leaf. Then changing to small steps I then have bands of softness where it has jumped too much

 

[tobiasash]

This online tool has Hasselblad X in the list of sensor/film sizes: https://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator

Thank you!

 

[bab]

I see the banding on the background?
the leaf curves downward the plane of focus does not!
imagine a drop of water sliding around a pipe when the water droplet is on top of the pipe or as it slides to the side or falls eventually to the bottom of the pipe even though it’s the same distance from the sensor plane that falling doward requires mant more small STEPS to get focus.

 

[tobiasash]

Hi Bab, thats a really good reminder. I appreciate your input.