How to determine the optimal interval size
Posted: 18.06.2020 02:11
Hello everyone,
now that I have had a chance to play with Helicon Remote and Helicon Focus a little more, I want to share my process for determining the optimal step size between images - meaning using the least number of pictures (prolonging the life of your shutter) while producing a sharp image without focus bands between.
First my setup: I am using a Canon M50 with a Canon F4 70-200mm L lens, and a Raynox 350 Macro lens & a LED Ring Light. Together, these sit on a WeMacro Rail.
I have established that each step in Helicon Remote corresponds to an approximately 0.1mm advance of the rail system (provided, I only lock in a starting point for the beginning of the stack). I then estimate the depth in millimeters needed, and start with a relatively low number of images, for example 1 image every 2 millimeters of depth. For example, for the Dobsonfly attached, I estimated 5cm total depth, which would result in 25 shots @ Interval size 20. My first run was at 70mm, F11, and EV-1. Of course the F-stop greatly influences your depth of field and the number of exposures needed.
Using Method B of Helicon Focus you can see a white on black inverse focus map during the second pass. If your focus depth is too shallow you will see dark bands between each layer. To remove these bands I had two options, either increase the number of pictures and reduce the Interval, or increase the F-Stop to 16. The uploaded examples include for examples of the inverted map, 100 shots @ Interval 5 (F11), 50 shots @ Interval 10 (F11), 25 shots @ Interval 20 (F11), and the final one with 25 shots @ Interval 20 (F16). The last one was then used for the final image.
Once you have established the optimal Interval size for each Focal Length and Aperture, you can write these down for future reference. This Interval size will not change as long as you maintain the same aperture and focal length.
Hope this helps someone.
-Iko
now that I have had a chance to play with Helicon Remote and Helicon Focus a little more, I want to share my process for determining the optimal step size between images - meaning using the least number of pictures (prolonging the life of your shutter) while producing a sharp image without focus bands between.
First my setup: I am using a Canon M50 with a Canon F4 70-200mm L lens, and a Raynox 350 Macro lens & a LED Ring Light. Together, these sit on a WeMacro Rail.
I have established that each step in Helicon Remote corresponds to an approximately 0.1mm advance of the rail system (provided, I only lock in a starting point for the beginning of the stack). I then estimate the depth in millimeters needed, and start with a relatively low number of images, for example 1 image every 2 millimeters of depth. For example, for the Dobsonfly attached, I estimated 5cm total depth, which would result in 25 shots @ Interval size 20. My first run was at 70mm, F11, and EV-1. Of course the F-stop greatly influences your depth of field and the number of exposures needed.
Using Method B of Helicon Focus you can see a white on black inverse focus map during the second pass. If your focus depth is too shallow you will see dark bands between each layer. To remove these bands I had two options, either increase the number of pictures and reduce the Interval, or increase the F-Stop to 16. The uploaded examples include for examples of the inverted map, 100 shots @ Interval 5 (F11), 50 shots @ Interval 10 (F11), 25 shots @ Interval 20 (F11), and the final one with 25 shots @ Interval 20 (F16). The last one was then used for the final image.
Once you have established the optimal Interval size for each Focal Length and Aperture, you can write these down for future reference. This Interval size will not change as long as you maintain the same aperture and focal length.
Hope this helps someone.
-Iko