Prinz Galaxy 135mm f/3.5 in UV - Not Too Bad!

[bvf]

Just to be clear - this is about the 135mm lens, not the 35mm.

 

A couple of years ago I got a Prinz Galaxy 135mm f/3.5 lens for some reason. The aperture wasn't working properly, so I got my money back but the seller didn't want it returned as it was only a cheap item. I found it at the back of a drawer yesterday, and partially dismantled it and managed to fix the problem. So I thought I'd try it in UV - which was probably why it was bought in the first place.

 

There are several versions of this lens, and an f/2.8 model. This is what the tested lens (with a T2-EOS adapter) looks like:

 

 

The same lens appears under other brand names, inc. Hanimar (Hanimex).

 

It has a typical solid, all-metal construction of lenses from the 1970s.

 

UV Reach

 

I checked the UV reach by comparing exposures through 380BP20, 345BP25, and 315BP20 filters and comparing filter factors normalised to 1 for the 380BP20. Here is a comparison against the UV-friendly Focotar-2 and the Yongnuo/Canon 50mm lenses compared in another recent post. The lower the filter factor, the better the lens transmission at that wavelength range.

 

 

The Prinz Galaxy is remarkably good at 345nm - far better than the 50mm lenses. But, like the 50mm lenses, it can't produce an image at 315nm.

 

This good performance at the upper part of the UVA range means it is probably OK for general purpose broadband filters like the Baader U.

 

Baader U

 

The following images compare the Prinz Galaxy with the Focotar 2 when using a Baader U filter. Images have been cropped so that they show approximately the same area.

 

In all cases, the Focotar-2 images are shown first. The left image has been WB-ed using PTFE, and the right image is with increased saturation. A couple of things to note about the Prinz Galaxy:

1. It was possible to WB against PTFE in the usual way - I was unable to do this when I tested the 50mm lenses.
   
2. Surprisingly the Prinz Galaxy is showing more yellow (representing the area around 350nm) than the Focotar-2, which has a much deeper UV reach. This is evident in the second image, and you can see it on the full resolution version of image 3 around the figure's heir and lapels. I'm not sure what's happening here.
   

 

 

 

 

 

 

 

 

 

 

 

Image Quality

 

These images compare the Prinz Galaxy against the Focotar-2 when using a Baader U filter.

 

The Prinz Galaxy appears to perform better at the corners at f/3.5 than at f/8! Obviously not what you'd expect. Initially I assumed a mistake, but a repeat of the exercise gave the same results.

 

[Stefano]

The only explanation I can think of about the increased false yellow, considering the good response you got at 345 nm, which is usually yellow/green, is that the Prinz Galaxy has a flatter transmission in the upper UVA range that plummets as you go lower (thus explaining why you didn't get an image at 315 nm). Odd, but this is the only thing that makes sense to me.

[Andy Perrin]

Or even has a peak near 345nm? Which would be truly odd lens behavior.

[Andrea B.]

Surprisingly the Prinz Galaxy is showing more yellow (representing the area around 350nm) than the Focotar-2.

 

I would not make any serious judgements about what false colour indicates because it is dependent on so very many different factors. (We listed those once somewhere.) For example, just a small shift with a white balance tool during conversion can create an alternate false colour set.

 

Everyone keep in mind that false colour is an artifact, a by-product of a particular combination of camera, filter, lens, flash, converter, white balance tool and more. Currently the various pieces of gear and software seem to combine in such a way that we can get a standardized false colour set, but it is not perfect.

[Stefano]

I agree that in general UV false colors are not a perfect standard, even if they are often very similar and predictable. But in this case the only thing changing is the lens. The camera is the same, the filter (Baader U) is the same, the lighting is the same... the lens seems to be the only real variable affecting the colors. It could be the white balance, but this was done multiple times (there aren’t just two images), and the results are consistent. Still, very odd behavior. It would be so interesting to scan the lens with a spectrometer.

[Andy Perrin]

Yeah, Andrea, I assume Bernard isn’t changing the white balance between images?? (Or if he is then I agree with you. But if all that changes is the lens, the false colors do tell us something.)

[ulf]

Without any actual facts I like to support Andrea's statement.

It contains very much sound facts.

 

To me it looks like a channel saturation thing.

Without seeing the histograms from the RAW it is difficult to draw any conclusions.

 

Are these images processed from RAW or are they a result of the camera's WB to jpeg?

 

The way cameras process images can be very strange and the image data for our images is far from typical from what the camera FW is designed to handle.

[colinbm]

Bernard, how can you get the dead same images with different lenses, are you using two cameras & firing them at the same time ?

[bvf]

I assume Bernard isn’t changing the white balance between images?? (Or if he is then I agree with you. But if all that changes is the lens, the false colors do tell us something.)

 

Effectively each of these images was WB-ed individually. I maintain a library of WB files for each combination of filter, lens, and lighting conditions (e.g. Prinz Galaxy under flash using Baader U; Focotar-2 in sunshine for Tri-colour UV). These are all generated from photographing a PTFE sheet under the appropriate lighting conditions and then WB-ing the image in RawTherapee. For a simple filter arrangement like the Baader U I apply the WB at the RAW stage; for complex filter arrangements such as the final adjustment of a Tri-colour composite I work from the TIFF.

 

In reality, there tends to be very little difference between the different lighting conditions and sometimes even between lenses. For example, I initially WB-ed the Prinz Galaxy PTFE shot using the Focotar WB files (because these include other settings, like "No Profile") - then when I set the white balance specifically for the Prinz Galaxy PTFE shot there was almost no discernible difference.

 

Without seeing the histograms from the RAW it is difficult to draw any conclusions.

 

Are these images processed from RAW or are they a result of the camera's WB to jpeg?

 

 

In all cases I started from the RAW. I applied the WB as mentioned above and then generated the JPEG (all in RawTherapee.)

 

 

I'm happy to provide the RAW files to anyone who wants to examine them.

 

 

Bernard, how can you get the dead same images with different lenses, are you using two cameras & firing them at the same time ?

 

Just one camera (on a tripod), with the images taken serially. The images were cropped to get a similar coverage. If you look closely, you can see differences - e.g. I had to move the cmaera between the indoor shots because of the different focal lengths.

[colinbm]

The two street scenes, the cars are in exactly the same spot ?

[bvf]

The two street scenes, the cars are in exactly the same spot ?

 

Ah, I see what you mean. The right-hand images are simply the left-hand images with higher saturation added in post-processing.

[colinbm]

Ah, I see what you mean. The right-hand images are simply the left-hand images with higher saturation added in post-processing.

 

Thanks Bernard, I misunderstood this..."In all cases, the Focotar-2 images are shown first." as left.

[ulf]

Ah, I see what you mean. The right-hand images are simply the left-hand images with higher saturation added in post-processing.

I did the same error as Col above.

[bvf]

I did the same error as Col above.

 

Must have ben my lack of clarity - sorry about that.

[Avalon]

Saw today this lens in vintage shop. Is this lens worth attention for UV photography or for example similar in design 4 lens element Soligor 135mm f/3.5 is better choice?

 

By the way where you get 315BP20 filter? Searched for it on Ebay and found none.

[Andy Perrin]

23 hours ago, Avalon said:

By the way where you get 315BP20 filter? Searched for it on Ebay and found none.

Bernard (bvf) doesn't come on here anymore. But I know the answer to the question. He got the filters from Omega Bob on eBay (who is now apparently rapidspectra, or at least that is his company). They were seconds, and they are probably long gone now. You could ask rapidspectra if they have any more.

[Avalon]

Cannot find nor seller, nor 315BP20 filter on Ebay. Nor I could find single 315BP20 filter outside Ebay. who is manufacturer of them?

[Andy Perrin]

I told you. Omega Optical makes them or made them. They were probably custom made and they were seconds that were not sold.

[dabateman]

Yes not many were made. Bernard contacted Omega about doing 3 wavelength UV and it was one of the suggestions.  Not many were available when they were available. 

I think I remember less than 4. 

You will have to contact rapidspectra to see what they have or what might be available. 

[ulf]

They have a search engine for their vast filter catalog:

https://www.rapidspectralsolutions.com/catalog#tutorial

I have not tried to use it, just looked at the tutorial above.