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Rodenstock apo rodagon D 75mm f4 on a7rii
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PostPosted: Mon Nov 02, 2020 7:28 pm    Post subject: Re: Rodenstock apo rodagon D 75mm f4 on a7rii Reply with quote
Gerald wrote:


OK, I know that the design was optimized for a 1:1 magnification, but the amount of LaCA, as can be seen in the pine tree in the foreground at the lower right corner, is surprisingly high for a lens that is said to be apochromatic.


Keep in mind that apochromatic means that the lens is corrected for longitudinal CA at 3 wavelengths. An apochromatic lens can still have lateral CA and be considered apochromatic.

Interestingly, from the charts for the 75ARD1, it isn't actually an apochromat, but a well-corrected achromat!


PostPosted: Mon Nov 02, 2020 11:04 pm    Post subject: Re: Rodenstock apo rodagon D 75mm f4 on a7rii Reply with quote
Gerald wrote:

OK, I know that the design was optimized for a 1:1 magnification, but the amount of LaCA, as can be seen in the pine tree in the foreground at the lower right corner, is surprisingly high for a lens that is said to be apochromatic.

This is normal for 1:1 optimized macros without floating elements, I think.
My Olympus 80/4 has poor infinity performance too.

Those macros of the yesteryear, that are indeed great for portraits and infinity shots will likely not match their 1:1 optimized counterparts in a, say, imaging integrated circuits around 1:1.


PostPosted: Thu Nov 05, 2020 2:18 am    Post subject: Re: Rodenstock apo rodagon D 75mm f4 on a7rii Reply with quote
aidaho wrote:
Gerald wrote:

OK, I know that the design was optimized for a 1:1 magnification, but the amount of LaCA, as can be seen in the pine tree in the foreground at the lower right corner, is surprisingly high for a lens that is said to be apochromatic.

This is normal for 1:1 optimized macros without floating elements, I think.
My Olympus 80/4 has poor infinity performance too.

Those macros of the yesteryear, that are indeed great for portraits and infinity shots will likely not match their 1:1 optimized counterparts in a, say, imaging integrated circuits around 1:1.


Another example of an optimized 1:1 lens is the Nikon 105mm Printing-Nikkor (105PN). Like the 75ARD1, it is optimized to have near perfect flat field performance, with constant MTF across the full field, at or near wide open aperture. But move away from 1:1 and the corners get fuzzy.

Mark Goodman tested an example of the 75ARD1 that I sent him and published the results on his excellent Macro Lens Test website here: http://coinimaging.com/lens_tests_new.html? Below is the graph of Corner Sharpness vs magnification at f4, showing how this lens is optimized for 1:1 and degrades at other magnifications. You can also find the 105PN (also sent by me to Mark for testing) at the same site.



PostPosted: Thu Nov 05, 2020 8:42 am    Post subject: Reply with quote
Indeed, this is an excellent lens Ray; happy to have it since years (amongst the others...)


PostPosted: Fri Nov 06, 2020 3:44 am    Post subject: Reply with quote
kds315* wrote:
Indeed, this is an excellent lens Ray; happy to have it since years (amongst the others...)


My favorite version of the lens is actually the fixed aperture type that was integrated into several scanners. I use microscope objectives quite a bit in my work, and actually enjoy not having adjustable aperture. I always push for highest image quality, which is either wide open or at the optimum aperture of the particular lens. Turns out the 75ARD1 is optimized to perform best wide open, so why stop it down? I have several such lenses that are fixed aperture versions of normally-variable aperture lenses, and they tend to be my favorite lenses to use.


PostPosted: Sun Nov 08, 2020 2:25 pm    Post subject: Reply with quote
I have the Magnagon scanner version and adore it, it may be partly due to my skills or lake thereof, but it produces by far the best results for macro work out of all my macro lenses.
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