Schott 2017 Filter Program - Graphs Compared

[Cadmium]

Yes, his test is old. His is the best Baader U spectrometer test I have seen however. Maybe time for an update.

The Baader U has its highest out of band leak around 900nm, just above 1E-04.

That is why extended leak tests using the Baader U will look white/gray instead of brown.

It is easy to show the difference in IR OD suppression between the Baader and some stack with the leak test, and the Baader U doesn't have as strong of optical density as the stack you mentioned.

Also, the Baader U has been known to attract slugs and snails, just ask Andrea about that.

 

Leak test comparison example.

[ulf]

Yes, his test is old. His is the best Baader U spectrometer test I have seen however.

???

 

His Baader U has its highest out of band leak around 900nm, just above 1E-04, but the peak at 700nm is much more important as the camera sensors are much more sensitive here.

When the light conditions are such that the ratio between IR and UV is unfavourable it the 700nm part is the one making the IR-leakage visible.

[dabateman]

Ulf,

Its hard to say which Baader filter is better.

Shane's:

http://www.beyondvisible.com/BV3-filter.html

 

Shane's 715nm peak is very small, but hard to put a number on it based on the plot. Shane's 900nm to 920nm chunk is definitely more intense, looking to be 4 fold more. All be it still very low. Without a proper small scale though its hard to know the real numbers. The comparison to the older 1.25 inch filter makes it hard to guess.

Your spectrum is much easier to read.

 

Mine has no detail, but my instrument wasn't very sensitive over all. If you squint the right way I can see some darkness at 920nm :)

My filter was purchased in October of 2008:

[Cadmium]

Since I don't have a spectrometer... :( I only have my Baader to do the leak test with.

Not sure what spectrometer Shane did his graphs with, he used some high grade type I think.

So that is all I have to go by with my Baader U, and I don't know exactly when I got it, I think maybe about 2011.

I can tell from the leak tests that my Baader U has the majority of its leak in the higher IR range, like 900nm, because of the color.

Of course, the whole point 'was' about the stack. It makes little difference really where the out of band leak is as, only how strong it is and if it shows up in the UV only shot.

So we really don't need to worry, because neither the Baader U or the Stack show in the usual UV shots.

[Cadmium]

Here is an old test using the Sparticle, comparing OD suppression of the

Baader U,

Schott UG11 2mm + Schott BG39 2mm stacked, and

Omega 330WB80.

All of these filters were stacked with Schott OG530, with 15 second exposure for each shot, to suppress everything below 530nm,

and to observe and compare the OD of everything above 530nm for each filter/stack.

NOTE: This is only an illustration, none of these filters/stacks show any sign of a leak when shooting UV only shots using optimal exposure times for the UV only shots.

 

I have included a graph for three stacks to compare the OD of the UG11 2mm + BG39 2mm stack with two of the popular U-360 stacks discussed here and above.

 

Here you see that the 610nm longpass filter shows transmission for the Baader U, and also the 770BP40. The Sparticle has no 900nm filter installed in these shots to examine that range alone.

However, notice that the UG11 + BG39 stack has no out of band transmission from any filter at the same exposure time as the other shots, not even the thin PTFE,

some might ask "why not the PTFE", because we are blocking everything below 530nm with the OG530 filter, and the UG11 2mm + BG39 2mm stack is blocking all transmission above 400nm.

So, this is simply to illustrate the difference in OD suppression between the Baader U and the OD5 stack.

Remember, the Baader U has an out of band OD of about 4 or 3.75.

The UG11 2mm + BG39 2mm is OD5, U-360 2mm + S8612 1.5mm is about OD5 or 4.75, and U-360 2mm + S8612 2mm is about OD6.

 

Note:

GG420 is a longpass filter and transmits everything above 420nm, so it will show IR.

610AELP is a longpass, and transmits everything above 610nm, so it shows IR.

770ABP40 has a peak transmission of 770nm, and a bandwidth 40nm wide (approximately 770nm +/- 20nm), so it shows IR in the 750nm to 790nm range (approximately).

Thin PTFE will transmit full range for the camera sensor.

 

 

[lukaszgryglicki]

Sorry, can you calculate a graph for me? Hoya U-340 4mm thick + S8612 2mm? Just wonder - because I'll have this non-standard one.

[Cadmium]

OK, but it isn't a stack I would recommend.

The whole point in using thicker than 2mm U-340 is so you don't have to use any S8612, and thus the UV range is not narrowed by the S8612.

However, U-340 4mm thick is not thick enough to suppress the Far-Red/IR enough to work on its own, you need 8mm, then you will not need any S8612, and you retain the wider range UV.

Also, if you have U-340 4mm, and you want to suppress the Far-Red/IR then you only need to use .75 to 1mm thick S8612 (S8612 1mm thick, let's say, because it is much easier to find than .75mm thick).

That stack will give you OD5 Far-Red/IR suppression, which is enough, more will only lower the UV %.

So, either use U-340 8mm or the 4mm stacked with S8612 1mm.

The best stack for UV is U-360 2mm + S8612 2mm. It has much better false color than any other stack.

 

Here is your requested graph.

[lukaszgryglicki]

Thanks, I requested only because I will have such a stack option - looks like it could be quite good for UV-only but I would need a very good lens. I'm really starting to consider UV8040BK2 again...

[Cadmium]

Myself, if I were going to get a thick version U-340 , then I would get 8mm, or two 4mm stacked together, then you get the full benefit and need no suppression.

Also, keep in mind that using thick U-340 will offset the UV band thus shifting the UV false color to more monotones, loosing most of the upper UV false colors. Not too attractive to me, but it is a different look.

I would much rather spend my money on U-360 and U-330, which will be more fun.

Below is an example comparing a U-340 8mm shot to a U-360 2mm + S8612 2mm shot. Both are basically UVA, but they don't have the same upper UVA blue/violet range, even the yellow is much more faint.

 

[Andrea B.]

I just tried out a U340 x 7.00 stack by stacking 3 filters: 4.0 x 2.0 x 1.0. It's getting very close to suppresion at 7.0 mm.

[dabateman]

The crazy thick 8.04mm zwb1 I ordered is good in cloudy sunlight without IR leakage. So I would assume U340 to act the same.

My shots were a little blurry though, being handheld at 1/3 shutter speed. So not worth sharing.

[Cadmium]

The crazy thick 8.04mm zwb1 I ordered is good in cloudy sunlight without IR leakage. So I would assume U340 to act the same.

My shots were a little blurry though, being handheld at 1/3 shutter speed. So not worth sharing.

 

I have no experience with ZWB1 8mm. I don't use Chinese filter glass. I have a ZWB1 1.5mm thick, I never use it, I got it for testing years ago.

Do you mean that you have U-340 8mm and it is blurry compared to your ZWB1 8mm?

Andy is showing the exact opposite in his photos:

https://www.ultravioletphotography.com/content/index.php/topic/4785-what-is-everyone-doing-with-their-8mm-zwb1/page__view__findpost__p__49366

 

All of the U-340 8mm shots I have are sharp..

[Cadmium]

I just tried out a U340 x 7.00 stack by stacking 3 filters: 4.0 x 2.0 x 1.0. It's getting very close to suppression at 7.0 mm.

 

7mm will give you OD 4.5 suppression. 8mm gives you OD 5.

[dabateman]

 

 

I have no experience with ZWB1 8mm. I don't use Chinese filter glass. I have a ZWB1 1.5mm thick, I never use it, I got it for testing years ago.

Do you mean that you have U-340 8mm and it is blurry compared to your ZWB1 8mm?

Andy is showing the exact opposite in his photos:

https://www.ultravioletphotography.com/content/index.php/topic/4785-what-is-everyone-doing-with-their-8mm-zwb1/page__view__findpost__p__49366

 

All of the U-340 8mm shots I have are sharp..

 

Sorry for the confusion. No I shot a test set outside, handheld with my now more shakey hands. And surprise I have motion blur from my shakey hands.

 

I was just trying to say that since Zwb1 does it, than for sure U340 should be good on its own at 8mm thickness.

 

[Cadmium]

I have not shot hand held with the U-340 4mm, however it has always looks as sharp as any thinner stack or even a Baader U.

I would have to look up the exposure times for all those.

I just saw the new tests by Andy in the other topic,

https://www.ultravioletphotography.com/content/index.php/topic/4785-what-is-everyone-doing-with-their-8mm-zwb1/page__view__findpost__p__49429

and I think his tests illustrate a huge difference. His ZWB1 looks very muddy compared to the stack.

I have not seem anything like that with U-340 8mm (U-340 4mm + 4mm glued or air spaced).