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Comparing Two Enlarger Lenses, Question About Adapters, Stepper Focusing

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 Posted 06/22/2016  8:49 pm Show Profile   Bookmark this topic Add Heavy_Metal to your friends list Get a Link to this Message Number of Subscribers
The first image is with a Nikon El-Nikkor 50mm the second one is with a Rodenstock Omegaron 50mm, both enlarger lenses. I noticed the color change between the lenses. Lighting was the same for both shots. Is the Nikkor more UV, IR sensitive? Or does the shutter speed of 1/15 vs. 1/8 affect the color? I figured the brightness may change, not the color.

When I compared the many pics I took for the session I felt that while the center of the coins seemed to have close to the same sharpness, the Nikkor was sharper at the edge of the coin for some closeups I tried.

Also it seemed like I could focus the Nikkor easier. The range of focus with the helicoid seemed greater for the Nikkor. That is, if I just nudged the the helicoid with the Omegaron the focus changed greatly. With the Nikkor I could adjust the helicoid a greater range and still stay in focus. I tried various stops from f/2.8-8 but the Nikkor just seemed easier to focus overall.

A problem I have experienced with higher magnification is vibration of the setup. Very apparent when I try manual focusing of the lens. I think that having the coin on a moving platform that is controlled by a motor with a hand held control or the PC would help to eliminate the vibration (in the camera). Anyone build their own?

rmpsrpms - I have ordered some adapters mentioned in a previous post you replied to, can you go back to that post "What thread size for reverse mount adapter..." and comment on what I need? Thanks

Comparing-Two-Enlarger-Lenses,-Question-About-Adapters,-Stepper-Focusing

Comparing-Two-Enlarger-Lenses,-Question-About-Adapters,-Stepper-Focusing
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 Posted 06/22/2016  8:57 pm  Show Profile   Bookmark this reply Add pepactonius to your friends list Get a Link to this Reply
Some lenses have a definite tint to them. Radioacive lenses often turn yellow over the years. I doubt that either of these lenses is radioactive, though.

What happens with the colors if you use the same aperture and shutter speed for both lenses?
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 Posted 06/22/2016  10:54 pm  Show Profile   Bookmark this reply Add rmpsrpms to your friends list Get a Link to this Reply
Lenses have different transmission properties for different colors. This is why a manual WB is usually needed.

Easier to focus is not a good thing. Comparing at the same aperture, the lens that is harder to focus is the higher quality lens.

I'll check out the other thread...
Contact me for photographic equipment or visit my home page at:
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 Posted 06/23/2016  01:24 am  Show Profile   Bookmark this reply Add coinphotofan to your friends list Get a Link to this Reply

Quote:
Easier to focus is not a good thing. Comparing at the same aperture, the lens that is harder to focus is the higher quality lens.
This is what I found out with my fixed aperture Rodagon 75ARD. I spend a lot more time getting it focused than with other 75mm or 80mm lenses. At first I thought the lens was defective, because I got blurry pictures with the same amount of effort I normally go through with other lenses. Later on I found that once in focus, it gives sharper pictures than any other lenses I have, even at 1:2 or 1:3 magnification. Another thing I noticed about this lens is that if it is exactly in focus, color fringing is minimal, but any slight off-focus (barely noticeable to the eye) will lead to pretty bad color fringing.
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 Posted 06/23/2016  6:23 pm  Show Profile   Bookmark this reply Add Heavy_Metal to your friends list Get a Link to this Reply

Quote:
Some lenses have a definite tint to them. Radioacive lenses often turn yellow over the years. I doubt that either of these lenses is radioactive, though.

What happens with the colors if you use the same aperture and shutter speed for both lenses?


No yellow tint. Read a post on the Net a while back about someone using the Jansjo lights, shining them into the lens for xx hours, to remove the yellow tint.

Will try using the same aperture on both lens next time around to see the results.


Quote:
Another thing I noticed about this lens is that if it is exactly in focus, color fringing is minimal, but any slight off-focus (barely noticeable to the eye) will lead to pretty bad color fringing.


Interesting. I'll have to spend some time comparing lenses, hopefully there are no issues. But the Nikkor does yield sharper images overall so far. Still, I need to make the whole setup more stable for macro pics. A $1,000 lens can't overcome vibrations in the camera or mounting system.

Just found an article where someone (David Hunt) used a hacked flatbed scanner, now disassembled with a camera mounted in it, to take stacked photos. I would think that's not stable enough but his pics looked just fine.
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