ulf Posted March 10, 2020 Share Posted March 10, 2020 I showed an ad hoc image with shot with my Fused Silica 150mm Ø50mm plano-convex lens from Oriel in Jonathan's topic about his 40mm lens.https://www.ultravio...dpost__p__33743The focus setting then was similar to the last refocussed one in the sequence below. Now I have made some tests with different apertures from f/8 and up. Without any limiting aperture the lens is ca f/2.3 and show massive spherical aberration making it very soft and hazy.For the second test I used an U-360, 2mm + S8612, 2mm stack. It is interesting to see how much focus shift and sharpness improvement I got at fully open (lacking) aperture. Link to comment
JMC Posted March 10, 2020 Share Posted March 10, 2020 Looks nice and sharp when stopped down Ulf. I must try a longer focal length lens with my setup at some point. Link to comment
ulf Posted March 10, 2020 Author Share Posted March 10, 2020 One thing that intrigues me is that the branch starting just a bit left of the center at the bottom edge is reasonably sharp in all but the fully open aperture-images.That branch is actually a three at 1/4 of the distance to the house I focussed on. At f/32 it has motion blur due to the 13s exposure time. Link to comment
Stefano Posted March 10, 2020 Share Posted March 10, 2020 I never saw a GIF (is it a GIF?) on this forum. Very interesting, you are getting really good, distorsion-less images with just one lens, quite impressive. Link to comment
dabateman Posted March 10, 2020 Share Posted March 10, 2020 That 135 format coverage looks good. Imagine just cutting out the center with 2x crop. That would equal what I am looking at with my lenses on the EM1. I don't know if my 25mm lens cover a 135 format sensor. I will have to test them on my DF, to know. Also I haven't tested to see if they will go to infinity. Link to comment
Andrea B. Posted March 13, 2020 Share Posted March 13, 2020 That is interesting, Ulf !I was wondering how diffraction might be playing a role here at the apertures beyond f/16? It appears that each stop down sharpens more even at f/22 and f/32. I think I was expecting a step backwards at some point as the apertures grew smaller. Between f/22 and f/32 some one raised a window covering. Link to comment
Andy Perrin Posted March 13, 2020 Share Posted March 13, 2020 Andrea, I noticed that too. I think it might be that the aberrations of the lens are still bigger than the diffraction effects even out to F/32 in this case. Link to comment
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