Lens test: Rodenstock EL-Omegar 1:35 50mm

[msubees]

This is a all plastic enlarger lens. No front or rear notch to open it for cleaning, nor has it any screws on the outside...

 

I used my hand to attach the filters and did not get good impression of its UV ability. but today's transmission test seems to suggest that it is better than the Nikon EL 80 (old version)?

 

test done similar to last time (need to copy data here), but zeroed with EL nikon older version at 600nM (=100% transmission).

 

Clearly, old version has better transmission at 330-360 than the new version of EL Nikkor.

 

But if I do not normalize among the 3 lens, data suggest that Rodenstock is the best? it beats the old El Nikkor all the way from 310 to 400nm.

 

Data format, in "Normalized" column, I zero-ed at 600nm with the Rodenstock lens. But for among lens comparisons, I think one should not try to normalize the machine. Unless one suspect that the light path is obstructed somehow for some lens, but not others.

 

Graphic format

[msubees]

I did some test shots yesterday morning. The UV images had the highest contrast wide open (F3.5?), then F4 is still acceptable. After that the images has haze on the right size and contrast drastically decreases (inspected on camera LCD). This is very strange! It suggests most of the UV was coming from the edges so when stopping down, UV transmission actually decreased disproportionally. I will post the photos later.

[Andrea B.]

Sure sounds like some kind of light leak effect.

All ports closed, viewfinder closed?

Is adapter tight to the mount and not letting any light leak through?

[msubees]

Andrea,

 

sorry I did not see your post but came to the same conclusion this morning! after seeing that the "haze" was changing directions, I realized it might be the aperture window...I blocked it and now it is fine! it might be better than my El Nikkor :) :)

every time I looked it before, I know there was a window that i need to block...but did not know it was the culprit for my poor photos.

 

so far I have not tried blocking the viewfinder window yet, for all my UV shots. I tried using my hand the other day and did not see an effect :)

[Andrea B.]

To see if you get light leak through the viewfinder, shine an ordinary flashlight into it while making a visible photo.

 

You might have been just lucky so far because you were blocking extra light thru the viewfinder by your body position while shooting. Or something like that.

 

Every camera I've tried so far can leak light through the viewfinder. Of course I have not tried them all!! :)

The pro Nikon bodies always have a viewfinder shutter to prevent this.

[JCDowdy]

I found a minor light leak on the LVF/LCD button on my DMC-G3.

A paper hole punch-out of black electricians tape worked, but if you work at it you can find other leaks.

Easier I think to just shade or drape the body than cover it with bits of tape here and there.

Oddly I do not notice my viewfinder leaks, but then it is only electronic.

[Andrea B.]

oh right ! EVFs aren't going to leak are they ?? :D I keep forgetting about EVFs as I'm only using optical stuff currently for UVIR work. So pardon my tunnel vision, so to speak. B) :)

 

Everything has potential leakage - port doors, loose LCD windows, aperture windows on lenses, openings around buttons and dials, slightly misaligned adapters, weird adapters like my Pentax Kmount to Screwmount. I have a couple of lenses which I cannot for the life of me figure out where they are leaking but they do.

 

We typically only tend to notice these types of leakages when we veer off the Visible path into UV land.

[msubees]

yes, my camera has EVF...i guess it does not leak light...i blocked the Rodenstock EL-Omegar lens with JB Welder epoxy glue last night....i think it is now totally dark.