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UltravioletPhotography

The Olympus 28/3.5 for UV


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Some years I purchased a few samples of the old Olympus 28 mm f/3.5 OM lens. These were dirt cheap (probably paid less than USD 60 incl. shipping for 2-3 lenses). A long time these collected dust only, until I decided to try it for UV. I built a dedicated ultra-short bellows focus device to allow a maximum wide focusing range with my Nikons. The lens head sits more or less inside the bellows. I had to replace the bellows material with a cut-down lens pouch in order to be able to compress the bellows sufficiently. The lens as of now focuses from at least life size 1:1 to infinity.

 

The setup is a little on the make-shift side, but due to its simplicity it actually works :D

 

A few snaps of the lens itself follows;

 

U201805164141.jpg

 

Front view of lens sitting inside the bellows (note to self: repaint nails before taking such snaps)

 

U201805164139.jpg

 

Rear view showing the bellows rails and the bayonet (with a CPU grafted onto it). The system is rear-focusing. I had to cut one of the rails at a slanted angle so I could mount my D3200 on it. For this setup, I only use the actual lens head and removed its focusing helicoid. The automatic aperture mechanism also was discarded so the lens now is stop-down only. No problem as I have CPU-assisted metering active.

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Well, we should put the 28/3.5 to use for UV photography. The optics do have coatings, but as this is an old lens (late '60s or so), the coating is probably not very advanced. A few test shots confirmed I could easily use Live View on my Nikon D3200 with its built-in Baader U filter.

 

Today I explored some dense dandelion meadows in my new neighbourhood. For a comparison I also brought one of my 105 UV-Nikkors.

 

Here is a typical result. Exposure was f/5.6 at 1/15 sec, ISO 800, on my D3200. The posted image is actually run through Zerene Stacker as I combined a few single images into one to enhance depth of field. The image shown is just 2 frames - the annoying spring winds buffeting the dandelion stems generated too much movement to yield sharp images over more than an occasional frame.

 

taraxacum 28oly_I2018051635132.jpg

 

This is not bad, not at all.

 

To put in perspective, here is the reference photo by the 105/4.5 UV-Nikkor. Exposure again f/5.6, ISO 800, but the much more UV-responsive special lens allowed 1/60 sec. I might even be able to get 1/80 or 1/100 sec on occasion.

 

taraxacum 105UV_201805163519.jpg

 

We immediately observe the markedly improved image contrast and clarity -- no surprise there, but that's not the point. The 28 Oly certainly is capable of recording UV floral signatures with more than sufficient quality.

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No. Just put it on my Nikon D3200, which has the Baader U (2nd gen.) internally. From what I can glean in the NEFs, the 28 doesn't go into any deep UV. Probably ends well above 350 nm. However, being only 2-2.5 stops less responsive in UV re the 105 UV is really good for a wide-angle lens.

 

It is quite sharp in UV, however, and thus behaves quite similar to my Tamron 21/4.5. Many of the ubiquitous 35/3.5 class, even when transmitting UV somewhat better, do less well in this respect. The 28 also appears to have little of the troublesome chromatic fringes sometimes found with non-specialist lenses for UV.

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So this bellows compresses enough to provide infinity focus on a Nikon 46.50 mm FFD? Olympus OM has 46.00 mm FFD. That's only .5 mm difference, but does the lens enter the chamber a bit?

 

Long FFD lens on shorter FFD camera => add spacers.

Short FFD lens on longer FFD camera => squeeze lens end into chamber if possible, but not too far !!!

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Infinity is no problem with this setup. The (limited) bellows extension makes greater than approx. 1:1 hard to achieve. At least on a continuously focusing system, however one could add extension but working distance becomes impractically short or even "negative" (inside the front element).

 

As I have removed everything except the lens optics and the aperture click-stops from the original lens, one gains a few extra precious mm at the rear end. Using the thinnest* "F" bayonet in my odds-and-ends bin helped as well. There is no danger of the rear lens cell getting into trouble.

 

 


* hint: the pre-70s bayonets are the thinnest. Those on the early E2 or M rings are perfect for the Olympus conversion. There are commercial OM>F mounts to be had as well, but they lack solidity and I would not recommend them.

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I suppose in theory as long as the fabric was flexible enough and lightproof, one could use any material for the bellows. I just got some black velvet which might work well.

 

This is so cool what you have done making your own bellows. Out of a Nikon lens pouch I think?

 

I just reread the original post and saw you removed the helicoid. That changed the lens FFD, yes?

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That bellows configuration is also very nice for focus stacking from 1:1 to infinity as the lens is stationary relative the motive.

I guess that was your intention as you run the Zerene stacker.

 

I once had plans to create a similar setup for VIS, but never found the time to do it.

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--I just reread the original post and saw you removed the helicoid. That changed the lens FFD, yes?

 

No. This is set by the optical design.

 

The pouch was just one floating around, a rather small sample which I believe came from a 10.5 Fisheye in its former existence.

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enricosavazzi

I suppose in theory as long as the fabric was flexible enough and lightproof, one could use any material for the bellows. I just got some black velvet which might work well.

...

... except in NIR. Most of the velvet types I tested are translucent in NIR. The fibers of the velvet even work like light guides to transmit NIR radiation from one side to the other of a velvet sheet.

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Bjørn: No. This [FFD] is set by the optical design.

ah! Thank you. Makes sense.

 

**********

 

Enrico: .....translucent in NIR

Thanks, Enrico. Good to know. I'm not surprised now that I think about it given that velvet seems to be made from polyester these days. Even the lovely Korean velvet I bought.

When I had velvet party dresses as a girl, I wonder what they were made of back then? Maybe silk/cotton blends? I'm not exactly ancient, but I do not recall polyester as a kid. Or maybe my grandmother simply refused to sew with it. I don't know. She always talked about buying "good cotton" materials. :lol:

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