New member's first attempts and questions

[Andy Perrin]

Reed when you mentioned a cheaper better IR blocker than the S8612, I thought you meant an off the shelf ionic filter. If its a custom proprietary dichoic, no problem. You are entitled to your intellectual property.

That's what everyone assumed, because otherwise why mention it at all?

[Andrea B.]

Have you ever tried it on anything but a quartz lens, Andrea? Remember the lenses most of the new people are attaching it to are substandard for UV. If you have a regular lens around with poor transmission, you could test yours on that and see if you get leakage.

 

Please see this topic: KolariU + Nikon 50/1.8 AIS

[Andrea B.]

This was the only UV pass filter available on Kolari's website, but it seems that they have other options hidden around the web for professionals that they don't sell to consumers.

 

I have never heard this! Companies don't hide things to sell only to professionals. They wouldn't make any money that way!

[rfcurry]

I truly apologize for the mention of ionic filters which are comparable to the S-8612, but less expensive. For years, I have been hearing the same statements setting the S-8612 as the optimum example of an NIR-blocking filter, with no equal. Yesterday, I foolishly mentioned otherwise. Mea culpa.

 

Perhaps someone would like to explore the possibilities of standard colored glass never mentioned on our forum. See http://opticalglass.com.ua/pds/flt/BGC/BGC29.pdf . I dealt with potapenko 10+ years ago and can say that their glass is high quality. Their prices were better than Schott, but I needed lower still. Phila Optics I never worked with. http://www.philaoptics.com/pdf/BGG29.pdf

 

Here is aa comparison based upon the stated stats of the companies -

http://www.uvroptics.com/images/Comparison.jpg

 

These are just two of the glassmakers/suppliers. You might also wish to examine the PG&F UVC* glass re: compared to Schott UG.

 

I apologize again for the disturbance in the force. :)

[rfcurry]

Andrea,

The Kolari image first shown had a green leak, not an IR leak, or so it seems. Ulf showed me once that I had a green leak in a filter he was helping me with. My Spectrophotometer displayed a spike at 524nm. The OD was still >4.0, iirc, however, the green leaked. A dandelion exhibited the green as seen in the OP pictures.

[Andrea B.]

I truly apologize for the mention of ionic filters which are comparable to the S-8612, but less expensive. For years, I have been hearing the same statements setting the S-8612 as the optimum example of an NIR-blocking filter, with no equal. Yesterday, I foolishly mentioned otherwise. Mea culpa.

 

Reed, I need some context here.

 

A. If you know of an ionic filter comparable to S-8612 but it is

• less expensive and also
  
• non-coated and also
  
• non-clad and also
  
• easily available from a typical optical glass supplier,
  

then that's one thing.

 

B. If there is an ionic filter comparable to S-8612 but it

• requires coating or
  
• stacking or
  
• special order from one of the typical optics manufacturers,
  

then that is another.

 

Please tell me which it is (without details) if you feel comfortable doing so.

 

I will also add from loooonnnnnng experience that there are truly no "secrets" in this game. However, both Birna and I respect and follow any manufacturer's non-disclosure agreements when testing or discussing filters or any other camera gear !!! I want to emphasize this. However, right now I don't think there are any "secrets" that I know.

[Andrea B.]

The Kolari image first shown had a green leak, not an IR leak, or so it seems.

 

There is a substrate which can pass green if too thin. U- something. Let me go look. We have mentioned it here somewhere.

(see next)

[Andrea B.]

Here is one discussion from JMC's crown-funded measurement of thin U-340, U-360.

I recall another discuss about U-340.

Note green leakage.

 

Transmission through thin (0.5mm) Hoya U-340 and U-360 filters

[Andrea B.]

Potapenko's S8612 seems to leak between 700-710. Oh well.

 

Potapenko's U-340 and U-360 has no green leaks at a 2.5 mm thickness. So these might be useful.

 

Nothing is ever easy......

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The thing about this glass stuff is that there only n ways to pour S8612 where n is probably 1 or maybe 1.2. So some company making S8612 either gets it or they do not. At least Schott has a good deal of quality control. Some of the emulators seem not to be following the recipe too closely! But I digress.......

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[rfcurry]

Andrea,

Thanks for looking up that green leak work. Very informative!

 

I wouldn't toss out the Gost BGC29 because there is a slight difference in the 700-710nm range from the S-8612. Imo, it is not a leak if it is shown in the specs so that you know to suppress those points. Besides, that glass is a 1mm thickness, you would probably use something thicker. Otoh, the curve from 80-90% is better on the Gost than the S-8612.

 

The Potapenko Gost BGC29 satisfies your "A" requirements, does it not? Anyone can contact Serge Potapenko and let their needs be known.

 

Cheers!