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UltravioletPhotography

My struggle with lenses


ahrneely

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Greetings, everyone!

 

A little history before I begin. I am a Canon shooter. I've been locked in to Canon since I bought my first SLR in 1994. You know the story: upgrade lenses, get a new body, buy more lenses, before you know it you're locked into a system by default of having spent thousands of dollars.

 

Back in the days of shooting film, I used to shoot quite a bit of Kodak EIR, and when I began looking into having my camera converted to return to shooting infrared I discovered the possibility of shooting UV. Rather than (potentially) destroying one of my "good" camera bodies (because who knew what would happen when having someone take apart a camera body), I purchased a used camera body from eBay. Because I'm a Canon shooter, and my goal at the time was infrared, I picked up a Canon 20D for roughly $50. I sent it off to LifePixel to have it converted to a full-spectrum/broad-spectrum camera, and crossed my fingers that nothing would go awry.

 

Meanwhile, I conducted a very small amount of research, and purchased an El-Nikkor 50mm f/2.8 lens and the corresponding equipment to mount said lens to my converted camera.

 

At this point, I've pretty much broken the bank on my annual photography budget. I had a bellows, extension tubes, and a focusing helicoid (all purchased through eBay) by the time my camera returned to me. Already owning decent infrared filters from my aforementioned days in film, I started shooting infrared and unfiltered "full-spectrum" with both the El-Nikkor lens and the array of Canon lenses I already owned, and I saved for the Baader-U filter.

 

As a birthday present, my wife convinced everyone in my family to contribute to my purchase of the Baader-U, and with that I started testing my Canon 20D in the ultraviolet spectrum in earnest. The only trouble was, due to the equipment I obtained, I was only really able to use the El-Nikkor for close-up or "macro" photography - which is not my particular favorite (mostly because I don't really have a way of stabilizing the front end of my bellows, so everything jiggles just a little bit), or mount the lens flush to the camera body and use my feet to find the correct "normal" focusing point.

 

Because I couldn't afford to look at different helicoids, or other lenses, I decided to test each of my Canon lenses. Having no access to fancy spectrometer equipment, the best I could do was snap each lens onto my full-spectrum Canon 20D and attach the Baader-U to each lens in turn. While I don't have empirical data (rather mostly visual data), I was still pleasantly surprised with the results.

 

The following image depicts the results from two lenses. The El-Nikkor 50mm f2.8 lens was mounted flush to the camera, without use of helicoid or bellows, and the camera body and tripod was physically moved away from the ColorChecker chart until focus was obtainable. The other lens is the Canon EF 50mm f/1.8 II, in practically the same physical position.

 

The setup is a standard Macbeth ColorChecker Chart, a Kodak 18% Grey Card, and a White Polytetraflouroethelyne Disc (inside a basket of clothes in my camper/trailer home). I'd love to hear some feedback from those with more knowledge and experience than my own on the difference in these two lenses.

 

Lens Test

 

After seeing these results, I went out and tested a living subject (a flower - I'm not sure the name of the species) and created a similar images as above to hear feedback on the UV portion of the image.

 

UV Lens Test

 

I think the only thing I am disappointed with is the amount of noise from the UV images, but with such a high ISO and a small sensor, it is no surprise.

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If the question is about using Canon gear, you already found the answer?

 

Many lenses can depict 'something' below 400 nm. The difference is more in how the final outcome appears, and its image quality. When you want a lens to perform deeper into UV, the challenge becomes harder for most lenses.

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Ahr, this was a good test effort. And it was nice to hear about you getting a Baader-U as a group present from your family. Cool folks!

 

It appears to me that the EL-Nikkor 50/2.8 passes a little more UV simply because of the exposure times shown - with the EL having the shorter exposure time. However the contrast looks better with the Canon 50/1.8 while the EL shot looks slightly washed out. This bothers me. So looking a little closer I thought I might be seeing some light leak in that EL shot? There is a streak on the left. And there appears to be a dark cyanish area to the right of the card and disc? This could be simply a side effect of your particular white-balance method. But can you verify for me that the EL does not have a light leak and that your viewfinder was closed when you made these shots?

 

Yes, you are going to get a much higher level of noise at ISO 3200. But shooting outdoors, as you showed in the flower shot, you were able to get a good f/8 ISO 200 shot with minimal noise in 25 seconds with that Canon 50/1.8. Granted 25 seconds is a very long time for shooting flowers if there are any breezes around, but it can be done. And there are other things to shoot which won't sway in the breezes.

 

BTW, that is a flower of the genus Impatiens, probably a garden hybrid so I won't try to guess the species. There is good detail and the false colours look good.

 

Given that the Canon 50/1.8 lens is useable for at least near-UV, I'm thinking that maybe you should just sell the El-Nikkor 50/2.8 ?? I'm pretty sure you could get back what you paid for the EL minus some small amount for Ebay fees. Next, be on the lookout for the old metal version of the EL-Nikkor 80mm. The EL 80 has a long flange focal distance and when mounted on an inexpensive Chinese focusing helicoid you can get infinity focus on the 20D. Then you will not be restricted to close-up work as you are with the EL 50.

 

You know, most of us started this way in UV photography - with a basic inexpensive camera conversion and a non-UV-dedicated lens. Then you practice and learn how to get the best you can from what you have and that experience will serve you well should you ever want to upgrade your UV gear.

 

Carry on !!

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You seem to be doing well so far. The 50mm EL Nikkor does have to short a flange focal depth to be very versatile on your Canon 20D.

 

If you are going to consider a longer focal length EL-nikkor, I would suggest you also consider the 75mm in addition to the 80mm. Aside from widening your options a bit, the 75mm may be easier to adapt depending on the length helicoids available. I say this because (I assume) that the adapted register depth of your M42 adapted 20D should be 45.46mm. Common inexpensive M42 eBay helicoid lengths are 12-17mm, 17-31, 25-55 and 36-90 with the 15-26 slightly less common.

 

The FFD of the 80mm EL Nikkor is 70mm and subtracting 45.46mm leaves 24.54mm as the maximum helicoid length that will permit INF focus. While close the 25-55mm helicoid is just barely to long to focus INF but a 17-31mm helicoid with a short (<7.5mm) M42 extension tube would permit INF. The shorter 17-31mm helicoid does sacrifice 16mm of helicoid extension relative to the 25-55mm but you would still have 14mm of helicoid extension for close focus.

 

The FFD of the 75mm EL Nikkor is 63mm which after subtracting 45.46mm leaves 17.54mm to achieve INF focus. The 17-31mm helicoid would focus a bit beyond INF but that is not such a bad thing IMHO and you have the full helicoid extension to focus up close if you wish.

 

I noticed that EOS to M42 adapters are plentiful and cheap with even chipped versions available for under $10. The same cannot be said for µ4/3 - just my luck! Score one for Canon!

 

Added:

I should clarify, that older 75mm without the illuminated aperture window would be less troublesome than the 75N which in addition to the light leak also allegedly has a longer 64.9mm FFD.

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Good suggestion about the old version EL75, JD. Thanks for adding that.

 

A generic suggestion for anyone adapting lenses using zoomer helicoids: don't get just one zoom helicoid for your particular camera mount, instead get the entire set of short, medium, long and extra long. That way you will have the heli you need for infinity focus and one or more of the remaining helicoids can be put to use for close-ups and macros.

 

Of course there is a limit there. When using my long helicoid on the UV-Planar, the lens gets so close to the flower subject that there is barely room to change filters. :o

 

I have helicoids which are M42-lens to F-mount-body for the D600 and also some which are M42-lens to M42-mount-body for the Pentax K5. Canon should be similarly covered.

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Thanks for all of the feedback, everyone! It is greatly appreciated.

 

It's been several years since I've studies physics, but the helicoid issue is one that has had me troubled. I fully understand the FFD and Register calculations needed to obtain focus at infinity, but I was having difficulty understanding the change in distance for focusing at something between infinity and macro (a portrait, for example). However, if I'm making the correct inference from JD's post, as my helicoid can focus at infinity and still give me room to "extend" the helicoid, I should be okay making that El-Nikkor lens closer to a "real" lens.

 

As it turns out, after my last post I was able to track down an 80mm El-Nikkor (with a metallic silver base) for about $30 on eBay, so I snatched it up and am awaiting it in the mail. I'll try to post more experiments as I complete them.

 

Thanks!

 

Ahr

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That is a great price on that 80mm, I hope it is in good condition.

Yes, you infer correctly, as "real" lenses have their own built in helicoids.

How long is the helicoid that you have?

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Canon body has a 44mm FFD.

Nikon EL80 needs 70mm.

So 26mm is needed in a helicoid.

If 17-31 heli is used, you should be OK for infinity focus.

 

Focus at closer distances on a helicoid depends somewhat on the original close focus range of the lens in question which, of course, changes when mounted on a heli. Which in theory should permit even closer focus. So this is why I recommend keeping a range of helicoids available depending on how close you want to get.

 

I'll go play with my 80 and see what I can figure out about closer focus.

 

ADDED 2:36PM

 

On my D600, the EL80 will close focus 22 inches from the front of the lens when mounted on a 17-31 helicoid fully extended. It is 5" more from the end of the lens to the sensor focus plane.

 

Nikon body has a 46.50 FFD. So I'm using 23.5mm of helicoid extension for infinity focus. This is all less than 5mm diff from the Canon, so I think Ahr can easily achieve portrait mode - and even closer - with an EL 80 on the 17-31 heli on the 20D. :D

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  • 1 month later...

Thanks for the info Andrea. That's a great help. I've got my eye on a "longer" helicoid for this lens. I have a very short one now and can just hit infinity with only it and the lens. I do have some extension tubes as well, and if I stack them just right I can focus at 5 feet. So, for now, I'm doing okay.

 

The 80mm that arrived is in "good" condition. There is a "barely noticeable" fogging in the lens (either fungus or scratches) that I think affects the contrast I am able to achieve, but doesn't seem to be affecting overall light performance.

 

Crossing my fingers it works okay.

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