Pros & cons regarding high transmission UV pass filters: Baader U (3 versions) & Chroma U-Bessel

[LarsHP]

34 minutes ago, Andy Perrin said:

No? Is that related somehow? 

No. I just wonder whether I could take out the filter and re-mount it in ordinary camera filter rings.

[ulf]

Tomorrow I'll try to find the empty Baader U filter ring I kept after remounting my filter, and measure the internal diameter where the filter was located.

[LarsHP]

Thanks, Ulf. 

 

What camera filter ring(s) do you use for your Baader U? 

[ulf]

My Baader U filter cell is made if two stacked step rings M52 - M48 and M48 - M52, to get the normal M52 threads on both sides as a normal camera filter.
Then there is a thin M48 retaining ring inside the rear M48 inner thread.

I do not remember from where that retaining ring came from. It might be from the BAADER-filter ring transplanted here.
The two rings are covered with a nice label I made.

 

The combined hight of this filter cell including the rear M52 filter threads is 9.6mm.

 

Sorry for the inverted view my camera phone gave me:

 

 

I have not used the Baader U for a long time, more than five years.

I prefer using my Ionic filters for that wavelength range for several reasons.

The Baader U has been sitting in a M62-M52 step ring that was putty mounted inside one of my Novoflex lens tubes.

[LarsHP]

Thanks a lot, Ulf. 

 

Your self-made filter holder looks nice with that label around it. It's obviously not a good idea to take that apart just to check what the diameter the glass disc is. I will ask Baader about it then. 

 

Interesting to know that you prefer other filter solutions. What are the advantages of your (supposed) stack? 

 

It appears difficult to find Schott S8612 filters, so I have concluded that a Baader U-filter (either the traditional Venus, or the new Sloan, which has better red+IR rejection) seems to be the best available option. 

[ulf]

I found my Baader UV/IR Cut filter that is mounted in the same type of filter ring as the Baader U.

 

The inner diameter of the filter threads with the threaded retaining ring is 47.6mm.

My guess is that the filter glass disc has a diameter slightly smaller than that, like 47.4-47.5mm.

That makes sense and matches my usage of step rings with M48 as the inner diameter of such rings also are around ca 47.5mm

I think I borrowed the retaining ring from the Baader U filter ring assembly for my self made filter holder

[LarsHP]

Thanks again, Ulf. 

 

What are the primary reasons you prefer other filters to the Baader U? 

[Andy Perrin]

9 hours ago, LarsHP said:

Schott S8612 filters, so I have concluded that a Baader U-filter (either the traditional Venus, or the new Sloan, which has better red+IR rejection) seems to be the best available option. 

Not THAT difficult? Andover seems to have it at 50mm diameter (they don't say what thickness, so better ask if they can do 2mm):

https://www.andovercorp.com/products/colored-glass/

 

[LarsHP]

Thanks, Andy. I'm in Europe and tried vendors here without any luck so far. 

[LarsHP]

On 2/28/2024 at 7:53 PM, Alaun said:

...

Hi, Alaun. 

 

I still consider the Baader U Sloan filter.

 

Have you had any problems with it; for instance flare?

 

Can you recommend it for UV photography of biological subjects? 

[Alaun]

Hi Lars! 

Actually, I did not have the chance yet to test it outside in the wild, only got it last week.

Also, just ordered an adapter, so I can use some different lenses (M42, 35mm Noflexar) on the D810.

So it will take some time, some more of spring and some sunny weather days.

 

[LarsHP]

1 hour ago, Alaun said:

Hi Lars! 

Actually, I did not have the chance yet to test it outside in the wild, only got it last week.

Also, just ordered an adapter, so I can use some different lenses (M42, 35mm Noflexar) on the D810.

So it will take some time, some more of spring and some sunny weather days.

Okay, that makes sense. I am in no hurry, but don't want to wait longer than necessary either, completing the UV set-up.

[Andrea B.]

Biological UV in low light condition.

 

Lars, what kind of biological subjects are you going to photograph? Will the subjects be a few feet from the camera or a few inches from the camera. Also, what supplemental UV lighting do you have planned? UV-flash or UV-LED torch?

 

Oh, sorry, I wrote "feet" and "inches". Please substitute centimeters, meters, etc. 

 

Knowing more about your potential usage of the UV-pass filters might help us make better recommendations if you don't mind providing more details. 

 

Also, is this filter needed for scientific work which will be published or for other kind of work? If it is for scientific, published work, then you need to make sure you have a filter set which does not leak any IR. And you need a light source which has an appropriate filter to block unwanted Vis or IR light.

[LarsHP]

Hi Andrea. 

 

Regarding the filter, I want to make sure it doesn't leak visual or (near) infrared in sunlight only, simply because this is the most challenging scenario I know of. I am not a scientist, but taking UV pictures that are halfway VIS-IR doesn't make sense. 

 

The "low light" scenario is regarding trying to make UV images indoors, where long exposure and high ISO will be natural consequences. For that, I have a Nikon D600 mono as well as a Nikon FE2 (film camera). Unfortunately, UV capable lenses aren't fast, and the extremely few that are, are Klaus Schmitt's. 

 

Regarding distance to subject, I expect most to be within 10 feet or (much) less, but don't want to limit myself to that. Doing landscape in UV may be something I want to do also. Sometimes it looks like taken with orthochromatic films. 

 

BTW:  I am surprised that I don't see a lot of discussion about using film for UV, including color film. Using film gets rid of the IR leak issue plus they typically have a quite good UV response. Current films include Kodak Tri-X among B&W films, plus some color films, I assume. Regarding current color film, it seems difficult to find spectral sensitivity graphs, which is needed when deciding which film to get for UV. 

[Andrea B.]

OK, shooting indoors....

 

You probably want to look into getting a UV-flash. I shoot indoors using a UV-flash fired 3 times. Once from the right, once from the left and once from the middle. If you use a UV-flash, high ISO is not needed. I rarely go above ISO-400 when at f/11, my typical aperture for UV reflected photos.

 

We have a lot of info about UV-flash. 

Lighting TAG Search

 

 

*****

 

I think that most folks these days are just not into film. We've never had much input here. What there is can be found here:

Film TAG Search

[Andrea B.]

I know you are in Norway and that there would be value added tax if you ordered the Kolari multispectral flash. So I am only showing you this to illustrate that such flashes are available. LINK

 

Perhaps somebody can provide a link to a European vendor who sells such flashes?

[dabateman]

Color film isn't so great for UV photography.  The yellow layer was most responsive for me with Kodak portra. Then the other colors were a stop away from each other. I didn't like the look and yellow I find hard to see.

[LarsHP]

Thanks, to Andrea, for your links and suggestions, and to dabateman for sharing your experience with color film.

[LarsHP]

On 3/4/2024 at 7:02 PM, Alaun said:

Hi Lars! 

Actually, I did not have the chance yet to test it outside in the wild, only got it last week.

Also, just ordered an adapter, so I can use some different lenses (M42, 35mm Noflexar) on the D810.

So it will take some time, some more of spring and some sunny weather days.

 

Hi again.

Did you get to test/try the U Sloan filter more?

I am particularly interested in how it behaves regarding possible IR leak (in the 1000-1150nm range) or any problems with flare.