Thierry,
Win some major points here ....... Market a metal adapter for your beautiful rosewood handles to fit other cameras.
Joseph
(RL3d owner, hint, hint, wink, wink)
So Rod, can I give up my rail for more accurate focus stepping?
Hi Darr ...
"but when does it matter if you focus with the front or the back if the plane of focus is stationary?"
The problem with Macro is that by changing the focus (therefore the distance between the lens and the film), you actually change the size of the image projected to the film. The more magnification of the subject the more you will see this effect. So stitching becomes potentially more error prone. If you use a macro rail to actually move the whole camera you'll be better off, but you are limited to how much of the subject the macro rail can accommodate.
By focusing with the back it is less of a problem but it's still there.
The big problem with focus stacking is the stuff that is wider than can be accommodated with your focus rail but still close enough that changing the focus changes it's size.
With regards to tilts. I am still working through the math and until I actually get an Alpa tilt adapter, will not really know if what I am seeing is true ... basically as you tilt, you loose DoF and need smaller apertures. It seems more and more that tilt will be quite limited on the new backs.
Paul
Paul,
When you tilt you actually do not lose depth of field and do not necessarily need to stop down more. When all is level and parallel, depth of field exists from a near plane to a far plane although you are only truly focused at one plane in between. However, when you tilt, the near and far planes form a wedge shaped 'V' with the hinge beneath the camera lens combination.
As the distance increases to a subject item, the depth of field increases as well. In most situations this means you can save some apertures, or not stop down as much as required by a straight shot. The caveat is, of course, if your foreground has verticals which take up at least 25% of the vertical heighth in the foreground, you can't use tilt if you want everything sharp as the principle plane of focus would transcend the vertical object and so top or bottom would be out of focus.
Someone above also was speaking of focus about whether it matters whether you focus with the front or rear of the camera. If you use the rear the lens to subject distance does not change and therefore the subject does not 'swell and shrink', as the lens to subject distance does not change. If you use the front to focus the size of the object will change and the image may show some of these artifacts if you are stacking. The smallest focus increments possible when using the front for focus stacking, will yield the best possible results, though perhaps not as good as using the back for focus.
The Arca R cameras, utilized as the front standard, gives the best chance for success with front focus, as it has the finest focus increment currently available.
This front focus issue is something many do not discuss but it is something that is there. Most front focus mechanisms such as found on DSLRs are not fine enough for best results. On the other hand it also has to do with 'GE' factor--'Good Enough'.
Good enough for my purposes. The photographer decides...
Rod
