Kolari Vision Hot Mirror Filter (UV/IR cut) vs S8612

[bsas]

So, I am studying those IR cut filters and thinking which one is better for UV.

 

S8612:

https://www.ebay.com/itm/Schott-S8612-58mm-x-2mm-UV-IR-Cut-Filter-Visual-Bandpass-IR-Suppression/293120993582

 

 

Kolari:

https://www.ebay.com/itm/Kolari-Vision-58mm-Kolari-Vision-Color-Correcting-Hot-Mirror-Filter-UV-IR-cut/290869671163

 

 

According to the graphs, the S8612 is 10% better for UV trasmission. But, did anyone ever tested both side by side since the price difference is huge (one is double the price of the other)?

 

Thanks!

[Andy Perrin]

S8612 passes UV very well, and while it is an excellent IR cutter, it’s NOT a good filter to restore a converted camera for visible light photos because it does not attenuate red light well enough. Our camera sensors are very sensitive to red and the whole image will be biased toward red if you don’t reduce it. The best Scott filter glass for the purpose is 2mm BG38.

 

I’m not sure how Kolari will compare to 2mm BG38.

[dabateman]

If you search the forum, I am pretty sure Cadmium has mentioned what the Kolari filter is equal to. Either a Bg38, Bg39 or Bg40.

We only really have 4 options. The Bg61 series isn't as good, and more expensive.

[bsas]

If you search the forum, I am pretty sure Cadmium has mentioned what the Kolari filter is equal to. Either a Bg38, Bg39 or Bg40.

We only really have 4 options. The Bg61 series isn't as good, and more expensive.

 

So, is the S8612 so much better then the BG38, BG39 and BG40 (if Kolari is similar to those) for UV, and if it is, how much better?

I really don't care about "restore my camera" hot mirror since I have a regular camera for regular photos. I am just trying to find the best/cheap filter or stack for my money with high transmission :(

Ans sorry, I tried but I cannot find details about the Kolari filter on the sticky filter thread.

[Andy Perrin]

You shouldn't use the Kolari filter for taking UV photos. That is not what it's meant for. (Similarly, don't use BG series for your UV, although you can get away with BG39, it's inferior to S8612 for that use.) Anything advertised as "UV/IR cut" is intended to restore normal camera function, NOT for use in UV pics.

 

So, is the S8612 so much better then the BG38, BG39 and BG40 (if Kolari is similar to those) for UV, and if it is, how much better?

You can see from the graphs above that S8612 2mm dips to 50% transmission at around 340nm, while BG39 hits 50% at 360nm. Since you want as much UV as possible, the BG39 is pretty bad by comparison.

[dabateman]

For your money the best and cheapest option is to go 52mm S8612, then $1 stepdown ring to fit on top of your 58mm other filters. 52mm is most common cheaper size.

PM Cadmium if he has any 52mm 2mm thick. I am only seeing 1mm now.

https://www.etsy.com/listing/287221717/schott-s8612-52mm-x-1mm-thick-uvir-cut?ref=shop_home_active_16

[bsas]

Is the 2mm filter so much better than the 1mm one? How much the thickness of the IR cut filter can influence it’s effectiveness?

 

Thanks! :)

[dabateman]

Yes get the 2mm one. The 3.5mm one is over kill. The 1mm one will not block the IR leak enough.

 

This is Cadmium thickness graph:

https://i.etsystatic.com/12308786/r/il/f2789e/992772109/il_570xN.992772109_i021.jpg

 

An other option is also Reed's filters here:

https://www.uvroptics.com/index.php?products

[Andy Perrin]

You have to understand how to read those graphs, though. The scale near the bottom on the diabatic graphs is roughly logarithmic, so you can tell the difference much more clearly than on a linear graph where it all gets mushed together. Each additional grid line at the bottom is another power of ten of blocking. You need to be below the 1e-3 line MINIMUM (and preferably much lower) to block IR successfully. If you go above the line anywhere in IR (except >1100nm), it will leak for sure.

[bsas]

You shouldn't use the Kolari filter for taking UV photos. That is not what it's meant for. (Similarly, don't use BG series for your UV, although you can get away with BG39, it's inferior to S8612 for that use.) Anything advertised as "UV/IR cut" is intended to restore normal camera function, NOT for use in UV pics.

 

 

You can see from the graphs above that S8612 2mm dips to 50% transmission at around 340nm, while BG39 hits 50% at 360nm. Since you want as much UV as possible, the BG39 is pretty bad by comparison.

 

OK, so, help me understand please (honestly, I am learning and the UV world is quite more complicated than I expected):

 

1) Why “shouldn’t use the Kolari”? According to their page this filters blocks IR heavily and let’s a lot of UV to pass:

“Not all camera lowpass filters have the same transmission. Ours is designed with aggressive IR blockage to eliminate IR leak on all camera models. Consequently, it also has more UV transmission than many cameras, for outdoor uses it is best to pair it with a UV filter, or even better, use it over our two spectrum conversion. See bottom of page for transmission curves.”

 

2) Looks like the Kolari curve is quite different than the BG39 curve. Am I mistaken?

 

3) Isn’t the S8612 also as “UV/IR cut”?

 

 

[Andy Perrin]

Yeah, so, the Kolari is intended as an IR cut filter for restoring visible light camera function. It passes a lot of UV, but it also cuts UV past 350nm (from their graph). The >350nm region is quite a lot of UV that you definitely will not want to be cutting. Most of what false color we get in UV comes from stuff between 400nm and 330nm (roughly) because past 330 the lens tends to cut the rest even with the "good" accidental UV lenses like the EL-Nikkor 80mm/5.6. So if you use the Kolari as your IR blocker, you will be missing a lot of the UV you want to keep and lengthening your exposure times and reducing the colors in your images.

 

Now, S8612 is ALSO an IR cut filter, but not all IR cut filters are created equal. S8612 is a fantastic IR cut glass type for stacking with Schott UG11 or Hoya U-360 glass to take UV photos with. What it does not do well is restore your camera to visible light functionality, which is what Kolari's filter is meant for.

 

I'm not at all sure which glass the Kolari filter is made of, so I can't answer that part. Not going to speculate.

 

Summary:

-Kolari and BG38 2mm are good for visible light pics

-S8612 can be paired with UG11 or Hoya U-360 for ultraviolet pics

-Kolari, S8612, and the BG glasses are all IR cutting (and UV cutting) to various degrees, but not all good for the same purpose. The proportions matter.

 

(honestly, I am learning and the UV world is quite more complicated than I expected)

As many have found before! We are pushing our equipment to the limits for purposes it was never intended for. The biggest cause of complexity is how little UV relative to visible/IR that we actually have available to work with in most light sources, particularly the sun.

[ulf]

You have to understand how to read those graphs, though. The scale near the bottom on the diabatic graphs is roughly logarithmic, so you can tell the difference much more clearly than on a linear graph where it all gets mushed together. Each additional grid line at the bottom is another power of ten of blocking. You need to be below the 1e-3 line MINIMUM (and preferably much lower) to block IR successfully. If you go above the line anywhere in IR (except >1100nm), it will leak for sure.

When stacking an IR blocking filter with most UV-pass filters the rejection around 700nm is often most important .

It is there most UV-pass filters have a nasty second transmission peak.

 

All ionic (not dichroic) UV-pass filters can be used alone for colourful IR photography using this secondary peak that completely overpower any UV content.

The resulting IR images get blue or purple skies if the sky is a part oft the motif.

[Cadmium]

No information is provided about the exact brand or glass the Kolari BG is.

However, in my opinion, the graph they show suggests that it is close to BG40 or BG38,

both BG40 and BG38 are good for visual. Some people prefer one or the other. I prefer BG38, and some prefer BG40.

S8612 is not good for visual, in my opinion, because it tends to look too blue for me.

S8612 and BG39 are essentially the same for visual, however, S8612 has a deeper UV reach, so it is better for UV stacking.

Thickness is very important, especially when stacking filters.

For visual, 2mm works fine.

You 'can' use S8612 for visual, but I think BG38 or BG40 would be best for that.

If you white balance from RAW out of camera with software, then you will get the best you can out of any of them, but ity is still best to pick out the filter that will work the best for visual,

and I suggest either BG38 or BG4 for that.

For you stacking you should use S8612, 2mm or sometime less for some stacks, but 2mm will usually work for any UV-only stack, and 'could be used' for visual, if it looks good to you.

Don't buy S8612 1mm unless you are doing something special and kind of obscure, like stacking with U-340 4mm thick, etc..

Rule of thumb, S8612 is about twice the suppression of BG40, so S8612 2mm is about like 2mm of BG40. So it would require about 4mm of BG4 to suppress like S8612 2mm dose,

I don't see much point in using BG39 for just about anything I can think of, because S8612 has the same suppression and yet provides better UV, however, you 'can' use BG39 for the same UV-only stacks,

and with most 'UV friendly lenses' you may not see a huge difference, maybe some exposure time, maybe some color palette loss, but it will work.

 

Let me know if I missed some question you had above.

 

PS: When it comes to visual, some look more blue, some look more red, that is basically all there is to it.

Here is how they compare:

Bluer < S8612/BG39 - BG40 - BG38 - Baader UV/IR-Cut > Redder

 

 

[Andy Perrin]

Cadmium knows what he is talking about because he sells the glasses, bsas. :-)

 

By the way when he says “can” in his comment...probably better not to unless you are in a McGyver type situation and it’s all you have around. In my opinion.

[Cadmium]

I say 'can', because I have seen people use it for that.

I also say 'can' because if you were to get some U filter (U-360, UG1, U-340, UG11) and want to use it for UV only, then your best choice would be S8612 2mm, and if that was all you had, then you could also use the S8612 2mm for visual, and if white balanced just so, it would come close to BG38 and BG40, but you might be more happy to use BG38 or BG40 for visual only at some point down the road...

It is good to point out that the UV/IR Cut filter in stock cameras vary, what they sometimes call 'hot mirror', technically a hot mirrors is not just a piece of BG glass, actual hot mirrors have dichroic coatings.

https://en.wikipedia...wiki/Hot_mirror

But back to the stock camera internal UV/IR cut filter,

those are not all the same, so no BG glass filter will work the same on all cameras, and no BG filter will work exactly the same as the filter that was in the stock camera,

you can only hope to come close.

That needs to be said, because they do other things to the internal filter, and the thickness...?

At one time, I tried to get my removed internal filter back from LifePixel, but they would not give it to me unless I paid for one.

I was going to send it to Shane, who at one time was scanning different one from different cameras.

In short, there is no one BG filter that duplicated the exact internal filter for any camera.

But I think you will find that BG38 and BG40 are the two that will work.

Here are some visual filter tests I did a few years back now:

https://www.ultravio...__fromsearch__1

[Andy Perrin]

I found on my Sony A7S and also the Sony NEX-7 that the S8612 in both 1.5mm and 1.75mm gave much too blue a result, even beyond what I could correct for in PhotoNinja without introducing noise.

 

Cadmium, your experience with LifePixel is making me even more determined not to use them again.

[Cadmium]

Andy, I tend not to want to put them down. Overall I have had good results and support from them, but I do have one camera that needs to be resolved by them, and the only reason it has not happened is because of my own procrastination.

I have a tendency to think that things may have been better when Vitally was around... seems like he may not be to evolved now, I don't know.

As far as the visual filters, well they keep those because I think they reuse them for people who send their cameras back to be converted back to 'stock'/visual use.

They sell those stock filters on their site... or use to, not sure now.

[ulf]

Andy, I tend not to want to put them down. Overall I have had good results and support from them, but I do have one camera that needs to be resolved by them, and the only reason it has not happened is because of my own procrastination.

I have a tendency to think that things may have been better when Vitally was around... seems like he may not be to evolved now, I don't know.

As far as the visual filters, well they keep those because I think they reuse them for people who send their cameras back to be converted back to 'stock'/visual use.

They sell those stock filters on their site... or use to, not sure now.

 

I still think it is strange if it was your camera that you sent for conversion. All parts of it was your property, even after they had taken them appart for the conversion.

If not clearly stated in advance that they would keep parts as a partial payment for the job, keeping and reselling parts of your camera it theft.

[Timber]

Cadmium are you going to cut S8612 anytime soon? I need a 43mm x2mm one ;)

 

 

[EDITOR'S NOTE: Vendor-members are not permitted to discuss business or sales in topics. Please make these requests via PM. Thanks!]

[bsas]

OK, I can feel all "Cadmium knowledge" going on my mind and I am convinced on the S8612 2mm.

Now my question is which UV pass is the best "pair" for it? UG11 or U360? My goal is to have enough trasmission that in broad daylight I can do some video on my NEX-7 ;D

[Andy Perrin]

I believe U-360 2mm and S8612 1.75mm or 2mm is a good combo? 1.5mm if you want to live dangerously for a tiny bit (few percent) more light. Video is more forgiving than still photos because you don’t notice the noise.

[bsas]

So, the transmission on U360 is better than the UG11? I am confused again :(

 

According to the sticky filter thread, the U360 is "72% for 2.5mm thickness between 290-400nm" while the UG11 is "up to 92% UV between 235-410nm". So, why the U-360 is better than the UG11 in my case?

[Andy Perrin]

Thickness matters a lot! But so does the peak location in the final stack. If the peak of the combined stack is too close to 400nm, it will give you lots of light but not much color.

You really need to see the plot for the actual stacks in each case. I'm sure we have them around here.

 

Regarding the thicknesses:

 

U360 is 72% peak for 2.5mm thickness, but UG11 is 92% for 1mm thickness. The transmission goes down exponentially with increasing thickness, so a millimeter or two matters. If you want to compare apples to apples, you have to work out what each glass would transmit at the same thickness. In this case, if you use 2mm of both of them, the peaks will be at:

 

T(U360 2mm) = 0.72^(2mm/2.5mm) = 0.77 = 77%

T(UG11 2mm) = 0.92^(2mm/1mm) = 0.85 = 85%

 

But that is for those glasses by themselves, not combined with S8612. There is a Schott program that Cadmium uses to do the calculations and plot the curves.

 

ETA: Ah hah, I found them. These are made by Cadmium.

 

The U-360 2mm + S8612 2mm stack has peak at 60% and wavelength 365nm (or so):

 

The UG11 2mm + S8612 2mm stack has peak at 50% and wavelength 358nm (or so):

 

So I guess the UG11 might give more yellows in the images, but less transmission and the U-360 would be blue-er but more transmission.

[bsas]

But that is for those glasses by themselves, not combined with S8612. There is a Schott program that Cadmium uses to do the calculations and plot the curves.

 

OK, a program can be really handy... Do we have access to that program or we need to ask Cadmium directly?

[Andy Perrin]

I pasted the graphs just now in the last post, but the program is free. I don't have the link, but I'm sure you can ask Cadmium.

 

By the way, there is also the matter of reflection losses. Note that the above graphs are for just the absorption inside the glass and doesn't include the effect of reflections. The reflections take away another few percent.