Andre's thread 'Experiment in Stacking'
Experiment in Stacking
had some discussion regarding the merits of focus rail versus focus ring with a couple of interesting articles linked.
Having read one of the articles from Zerene
https://zerenesystems.com/cms/stacke...ringversusrail
it mentions the "
change in shape" (
as opposed to the obvious change in scale) of the subject between the nearest and farthest shot when using a rail which is the first time I had heard of this. The article shows a gif where it can clearly be seen what he refers to.
So being my normal inquisitive self I decided to set up a test to see if I could replicate this and if I would come to the same conclusion.
Firstly, in this thread it is not my intention to prove or disprove the merit of either method, or do I have enough experience from using both methods to have led me to any conclusions.
1. Test intention
Using both focus rail and focus ring (
two separate tests) to take a shot of the near edge and then the far edge of a subject and see if these can be superimposed on each other after correcting for the 'scaling' differences and to see how much "change in shape" was apparent with the rail use.
2. Test Method
Camera set on tripod with focus rail. A small aperture was used to get max DOF to get best clarity when the two shots were merged. The subject was a 50mm diameter shot glass. Camera D800 with 105mm VR micro Nikor
For each separate test the start point (nearest) was with the camera/lens at the stop point on the rail with the lens focused on the near rim. For the rail test the rail was wound forward for the second shot to the point where the rear rim was in sharp focus. For the focus ring test the lens barrel was rotated to the point where the rear rim was in sharp focus.
The four shots were opened in PS and titled. (
Note, the titling was placed in exactly the same position within each frame with respect to the bottom left corner).
For both the Rail and Ring test shots their 'rear focused one' was merged onto the 'front focused one' at 50% opacity and 'scaled' to align.
3. Results
Using Lens Focus Ring
Using Focus Rail
I can detect 'no change in shape' with the focus rail example as seen so obvious in the Zerene article, why? What have I done or used differently?
Grahame