pbraymond wrote:
Rafael, I wonder is the same is true of the tiny 20mm f3.5 (52mm filter version). I had some shots today with unsatisfactory sharpness beyond the DX frame, and I tried f8 and f11, and should have had enough depth of field to cover the edges somewhat. Anyone with any experience to share?
I am simple minded, this is how I see it: almost all the 15mm to 20mm older Nikkors have much more depth of field at the center than the edges and corners, and also some field curvature; so you must choose which corners matter to you, and look at them as you focus the lens for the entire image. Your near and far corners are not likely to be equally sharp at any aperture.
One can end up with equally sharp center areas with very different looking corners from small changes in focusing.
Some, like my 15mm 5.6 and 18mm 4.0 are more forgiving, you can set them to infinity and, for the normal standing up position, the near corners will be decent at any aperture. Of my lot, (which includes 15mm 5.6, 15mm 3.5, 18mm 3.5, 18mm 4.0, 20mm 3.5 UD, 20mm 4.0, 20mm 2.8) The hardest to get right are the UD and 4.0, but these can be used just fine with some corner attention, as my two Laguna Beach shots show.
But yes, just setting to f/11 and focusing on the center is likely to give you bad corners for all of them.
Here is some evidence from the UD, just look at the lower left corner soda bottle.(aperture was f/11, not the camera data)
Tuesday and Wednesday here were very hot with high humidity. Wednesday I went out in 96 degree heat to check on the Echinacea - which were wilting with pedals pointing straight down. I watered them and put up an umbrella on a table about five feet away from a clump of three kinds of these cone flowers. Within 30 minutes the pedals revived just as I arrived with tripod, 5DS-R, 200mm f2.0 ai, plus 36mm of extension tubes. The tubes brought the MFD down to about 40-45 inches. Sitting in the shade I shot these focus stacks in my mini Echinacea study.
rafaelcasd wrote:
I am simple minded, this is how I see it: almost all the 15mm to 20mm older Nikkors have much more depth of field at the center than the edges and corners, and also some field curvature; so you must choose which corners matter to you, and look at them as you focus the lens for the entire image. Your near and far corners are not likely to be equally sharp at any aperture.
One can end up with equally sharp center areas with very different looking corners from small changes in focusing.
Some, like my 15mm 5.6 and 18mm 4.0 are more forgiving, you can set them to infinity and, for the normal standing up position, the near corners will be decent at any aperture. Of my lot, (which includes 15mm 5.6, 15mm 3.5, 18mm 3.5, 18mm 4.0, 20mm 3.5 UD, 20mm 4.0, 20mm 2.8) The hardest to get right are the UD and 4.0, but these can be used just fine with some corner attention, as my two Laguna Beach shots show.
But yes, just setting to f/11 and focusing on the center is likely to give you bad corners for all of them.
Here is some evidence from the UD, just look at the lower left corner soda bottle.(aperture was f/11, not the camera data)
Serge,
Thanks for the explanation. I'm not sure I understand it all completely (especially about the edges having less DOF) but I can see the issue of managing the in-focus parts of the image with very selective focusing. Really happy to be shooting mirrorless from this particular perspective; don't think I would be motivated enough with a DSLR to manage that focus plane thru an optical viewfinder. The two pictures above took that into account. It definitely helps, though in all honesty the far corners don't really fully sharpen up but that is fairly normal for lenses from this vintage. I think the old saying was "that portion of the frame is hidden under the slide mount anyway". I will continue to experiment.
Hi all, been real busy planting olive trees, taking pics for the Navy that I cannot show you, fixing cars, linking sats, making sure helos can land, feeding dogs, playing computer games........
rafaelcasd wrote:
Hi all, been real busy planting olive trees, taking pics for the Navy that I cannot show you, fixing cars, linking sats, making sure helos can land, feeding dogs, playing computer games........
Serge, my 20mm f3.5 is not Rafael class (with some paint loss, dented but still functional filter ring) but manages to perform well enough, and performs well beyond what it's modest size would suggest. Even with the FTZ it's smaller and shorter than a Z 20mm (though to be fair that's an f1.8). Another sample, first an establishing shot with the 20mm f3.5 AI, then an abstract-like shot with the 55 f2.8 Micro. Did not quite plan the abstract but liked how it looked in the VF and with just the slightest crop to butt the piers against the sides.
Who thought this was a good idea?
