Lou Jost wrote:I'm very excited about these results, Robert. I've been fiddling with the aperture settings of the Componon to see if I can get good corners in FF, and I have found that by closing down the tube lens to halfway between f/8 and f/11, and closing down the front lens (using its own aperture) to f/4, I get acceptable corners. Astigmatism is strong n the corners when the tube lens is wide open. This can be reduced by using Zerene DMap instead of PMax, but it doesn't go away until the rear lens is stopped down to the level I just mentioned. The exposure hardly changes when the rear lens is stopped down this way. It starts changing when I go beyond about f/9.5.
Now I'll try the right way to stop the combo down, using a paper aperture between them, as Robert used.
That is interesting Lou, thanks for sharing the details.
I've also seen some improvements to stopping down the rear lens with the limited amount of experiences that I've tried it so far without any negative effects on the image, at least so far. I need to remember to try that more often.
In testing I've seen that some lenses respond to additional distance between the main and front lens (like a microscope objective).
In the past I've always tried to get the front and rear lenses as close as possible, almost touching, but I've found thats not always best. Some lenses do better in the corners with 25mm or 50mm between the two.