[Filter Test] Blocking UV for Visible Photos Made with Full-Spectrum Camera: Part #1

[dabateman]

14 minutes ago, aphalo said:

T* is the name Zeiss gives to the antireflection multicoating they use on objectives, binoculars and filters. The original T* from the 1970's has been improved since then according to Zeiss' web pages. The UV T* filter has a very sharp cut-in near 410 nm, which suggests a dichroic (interference) filter type. The data sheet is available online.

 

Not really, long pass filters aren't too hard with standard glass. I don't have one, but there is no reason for it to be dichoic,  just because it has a sharp cut off at 410nm.

I have a bunch of Astrophotography filters that are absorption based and also have sharp cut offs.

[Andrea B.]

Everything and more about Zeiss AR coatings and how they work: 

https://pixinfo.com/wp-content/uploads/2016/04/en_About-the-reduction-of-reflections-of-camera-lenses.pdf

 

There is an interesting little side note in the PDF about Zeiss's use of computers on page 61.

 

Added Later:  I looked through a lot of the linked PDF. There was a discussion of vacuum dispersion as a way of coating. But I couldn't find anything else mentioned about the Zeiss coating method.

[Andy Perrin]

2 hours ago, Andrea B. said:

 

 

But I wanted to respond to Andy's suggestion of the Kolari Vision UV/IR Cut Pro Hot Mirror 2.

 

• No, I'm not going to test that filter for now. Maybe later. That Kolari hot mirror is just coated BG38. It cuts in around 320 nm. For our purposes that seems to be quite a lot of UV passed. Indeed, I question the naming of this filter as an UV/IR Cut.

 

Andrea, NO NO NO:  That is the OLD Kolari UVIR cut you are thinking of! I am referring to the BRAND SPANKING NEW (but not, hopefully, shiny) one! Note the all-important "2" on the end of the name.

https://kolarivision.com/product/kolari-vision-uv-ir-cut-hot-mirror-pro-2/

 

This one has 50 layers of dichroic coating on it to cut UV at (it looks like) 420nm.

[Andrea B.]

Gotcha! I zipped right past the chart for the Kolari UV/IR-Cut 2 thinking it was only showing camera internal filters.

 

I got it now. And indeed the newest UV/IR-Cut 2 is definitely worth testing.

I have ordered the Kuvircut. Looks really good, doesn't it?

 

 It is a laminated stack of two filters. But hard to tell whether the coating is dichroic.

I'll figure it out when it gets here I guess.

 

Thanks for the note on this, Andy.

I'll correct the error above, too. And mention the new Kolari in the Summary.

[Andrea B.]

The Zeiss T* UV-Cut filter has arrived. It sits in a very pretty, clear, easy-to-open hinged box. (The little hinge is metal!). The filter itself seems to have no tint at all. So the UV/blue blocking is not done with any kind of yellow glass. The surface feel is ever-so-slightly "draggy" to touch. Please don't go touching all your UV-cut filters though. I really didn't mean to fingerprint mine immediately upon opening. It was an accidental hand fumble!

 

The Kolari UV/IR-Cut arrives this Saturday. I had an email note from Ilija at Kolari Vision offering me a review copy which was very nice of them, but I always buy my test gear in order to keep UVP non-monetized. I'm really looking forward to trying this new UV/IR-Cut filter after making the above tests with the BG + Longpass stack. It fills a real need for those of us who want to use our converted cameras for Visible work and have had some difficulties with the Baader UV/IR-Cut's reddish tones.

 

 

[Andy Perrin]

Andrea, I ordered an STC clip-in filter with a 615nm cut (recommended as most like Sony original white balance) STC clip filter, which should come sometime soon. I want to see how well it does at cutting the UV and also the ghosts/partial reflections I see when photographing bright lights directly facing the camera (e.g. the moon).

 

Manufacturer links the spectrum here:

[Doug A]

@Andy Perrin sounds interesting. Looking at their page, bullet point #2 says Japanese glass. The specs say Schott. Wonder which it is? Either way looking forward to your review.

Thanks for sharing,

Doug A

 

 

[lukaszgryglicki]

I have Kolari UV-IR cut (bought together with UV-Pass) - for me it works OK, not ideally, OK. It has blue tint - but waaaaay less than S8612 - actually it's almost transparent, unless you look on it from an angle.

 

 

[Andy Perrin]

1 hour ago, Doug A said:

@Andy Perrin sounds interesting. Looking at their page, bullet point #2 says Japanese glass. The specs say Schott. Wonder which it is? Either way looking forward to your review.

Thanks for sharing,

Doug A

 

 

Doug, the bullet says Schott B270 which makes no sense whatsoever since that stuff is transparent from UVB to MWIR. I’m going with Japanese IR cut glass. Whoever makes that! Hoya, maybe?

[colinbm]

They don't look very useful to me....

[ulf]

One problem with clip in filters is the risk for getting dust on the sensor.

They are not that practical either if you want to switch between filters often, as I normally do.

 

I started with some clip in filters from Astronomik.de for my Canon 60D, with a APS sensor.

On my to do list is to sell them, likely on eBay, but I have been too busy (or lazy?) for a long time to do that.

 

If anyone here is interested, please message me privately and I can tell more.

[Andrea B.]

I've sometimes wanted a clip-in filter to use when I want to dedicate one of the conversions to a shoot using just one waveband. Example:  I love to go out equipped to make R72 IR photos (only) for an afternoon. 

 

And for those lenses which need rear filtration, a clip-in is just the ticket. Some interesting little enlarger lenses I have don't support front filtration easily.

 

So, as usual, pros and cons on any of our gear choices...

 

Japanese IR cut glass. Whoever makes that! Hoya, maybe?

Hoya is Japanese. But these days, it could be any Japanese optical glass company.

[Andy Perrin]

Yeah, my normal use pattern is to shoot in only one band for a whole day. Switching filters is a huge pain when I’m out walking and there aren’t even any places except the ground to put my bag down. 

[lukaszgryglicki]

I usually just take a one camera, one lens & one filter (set) for a walk. Then I eventually blame that I took the wrong set (after processing RAWs - sometimes I see that all of them are just bad).

[Doug A]

I have drageverythingalongitis. Working on UV/IR only camera bag. 

 

Thanks,

Doug A

[Andy Perrin]

Doug, when you have to carry all of it, that disease tends to go away by itself.

[Andrea B.]

I don't think my scene was well chosen for the test.

I'm going to try again in Test #2 here:  https://www.ultravioletphotography.com/content/index.php?/topic/5088-filter-test-blocking-uv-for-visible-full-spectrum-photos-part-2-just-getting-started-pls-offer-suggestions/