Some ideas

[Stefano]

Yes, I found that in sunlight the Invisible Vision did let some IR through. However keep in mind that the actual amount of UV at around 308nm in sunlight is absolutely tiny, while the IR levels are huge. So is it a surprise that when used for imaging in sunlight that some IR gets through? My copy showed very good blocking up to about 800nm which is as far as I can measure. It was definitely in the >OD3 range. However yes, adding a 4mm U340 would be a good test.

 

What light source (and lens) were you using? I normally use the Invisible Vision filter with a UVB light, so in that case it does not need extra blocking.

Imaging UVB is not easy, and if OD 4 is enough for UVA, I think that at least OD 6 is required in UVB to really remove any visible IR leakage.

 

The lens I use is the stock lens of my camera, a Panasonic DMC-F3.

 

 

 

This were from a previous post. I don't have any glass cover above the sensor, and I can be sure that this lens doesn't have a lot of glass. Regarding filters, I have a "light" one and a "heavy" one. The first is a ZWB2 (2 mm) + BG39 (2 mm). The heavy filter is a ZWB1 (3 mm) + BG39 (2 mm). Since I use tape to hold them, I don't change them often. Now I have a 7 mm stack (all of them, ZWB1 (3 mm) + ZWB2 (2 mm) + BG39 (2 mm). I can barely record a video, and I obtain a correct exposure at f/2.8, ISO 80 and 60 s exposure on a cloudy day photographing leaves (which are UV-dark). But I can not white balance in camera if I use it in "starry sky" mode, which is what I did.

 

f-stop: f/2.8, ISO 80, 60 s exposure. Heavy filter (7 mm stack), cloudy day.

 

Otherwise, I can be a lot faster with the light filter, I can white balance and I also have a lot more color (or colour, since you are from UK).

As an example,

 

f-stop: f/2.8, ISO 1600, 1/8 s exposure. Light filter.

 

Same everything.

 

I don't have a lot of luck with them. Either they are perfectly focused but the colors aren't nice and you can see my fingers, for example, or the colors are nice but I am out of focus. I can not manually focus.

[SteveE]

I even wonder about the Samsung TV sometimes laaaaaate at night.

When I got my Samsung flat screen, I hooked it up to the net. The router is close by and the activity lights on the TV's link began to blink furiously. I figured it was just updating the firmware. Two hours later, the network traffic was still going strong, so I unplugged it from the network and have left it that way.

[Andy Perrin]

Stefano- you won’t get anywhere near UVB with that lens and filter setup. From the photos, you aren’t getting much lower than 365nm at a guess? Even with appropriate filters you need quartz lens to get UVB.

[Stefano]

Yes, I never tried UVB. I didn't notice that JMC was referring to UVB, I would have edited it later in my post. If I am lucky I can go down to 340 nm, probably not more than that.

[Andy Perrin]

You should buy an Omega 330WB80 filter (in my opinion these are a must-have for all UV photographers who use telephoto lenses). They can be bought on eBay from bjomega. They are typically 25mm. They have pretty good blocking including IR. They pass the middle of UVA well and attenuate the long waves near 400nm that typically obscure the shorter waves.

[Stefano]

Also a thick Hoya U-340 will attenuate the 380-400 nm region (imagine a 7 mm thick filter)

[Andy Perrin]

Hee. Don't do that. One, you will have to special order it, and two it will probably make an inefficient stack. The 330WB80 is a nice thin dichroic filter and it works very well provided you don't have a wide-angle lens.

 

I am trying to recommend it as a general purpose UV filter for you, not specifically to attenuate the 380-400nm. I mentioned that issue just because it tends to obscure some of the color you can otherwise get from the shorter waves. Also it is pretty cheap for a good UV filter.

[Cadmium]

Actually, you could stack U-340 4mm + U-340 3mm together and get a nice 330WB85 filter with MOOB OD4.5. Or you could stack U-340 4mm + S8612 1mm for a 340WB50 with the same MOOB OD.

You will need a "real" UV lens (UV-Nikkor, etc.) to realize any potential, otherwise you are going to loose when using such a filter on any 'accidentally' UV capable lens.

The parts are available...

Or you could get something like this if you want more like a 52mm size with higher UV peak amplitude:

https://www.primaluc...ltraviolet.html

 

I think this is the same filter.

http://www.savazzi.n...alucelab_u.html

[Stefano]

Look at this graph. Hoya U-340 is an awesome glass. This is for a 7 mm thickness, internal transmission. Peak at 340 nm, around 70%, OD 4.5 at 710-720 nm. Cadmium (Steve) makes better graphs than me, I only have Excel.

 

(I forgot the image)

 

Edit: I didn't see the previous post, that's why I repeated what you said.

[Cadmium]

Yes, that is the U-340 alone, at about 7mm thick. Keep in mind the peak T will be lower than what your graph shows there. That is Ti.

 

[Stefano]

Yes, that is the U-340 alone, at about 7mm thick. Keep in mind the peak T will be lower than what your graph shows there. That is Ti.

 

Do you remember a person on Ebay asking you if you could make this filter, some months ago? I was that person.

[Cadmium]

Unless you have a slicer, and slice from a block, then sheets are 4mm thick, so anything thicker than 4mm would need to be glued using combinations of thicknesses that add up to what you want the total to be,

gets expensive either way.

ITOS has a slicer, ask them how much a 7mm thick filter would coast, it won't be cheap, but who knows.

I think the Optolong may be something to explore, it is the same band width, but it would be a stronger peak, it really depends on OOB suppression/leakage.

[Stefano]

Or you could stack U-340 4mm + S8612 1mm for a 340WB50 with the same MOOB OD.

So this would be equivalent?

[Andy Perrin]

What is “MOOB”? I use filter glass (1.75mm S8612 + 2mm UG11) because it works better at wide angles. But the 330WB80 improved is small, thin, and cheap. It is blocked to OD5 past 800nm. It is currently $59.50. Anyway you could build a small stack I guess but for a small camera lens it seems like the dichroic is more convenient.

[Stefano]

I think "MOOB" means "Maximum Out Of Band"

[Andy Perrin]

Ah. I was going to say, I don’t think cows take UV photos yet!

[Cadmium]

I think "MOOB" means "Maximum Out Of Band"

 

Hmm, well I made it up, I actually meant it to mean minimum out of band, but we need to redo that given that min and max both start with M!

The more I think about it, I am not even sure if I should call it min or max, which is it?

I need coffee...

[Cadmium]

What is “MOOB”? I use filter glass (1.75mm S8612 + 2mm UG11) because it works better at wide angles. But the 330WB80 improved is small, thin, and cheap. It is blocked to OD5 past 800nm. It is currently $59.50. Anyway you could build a small stack I guess but for a small camera lens it seems like the dichroic is more convenient.

 

When you use a more standard stack like 2 + 2, as you describe above, you get a higher peak nm. That is what happens.

If you want to move the peak to a lower nm, then you use a more heavily weighted U thickness, if you want to move it higher, then you use a thinner U thickness.

Moving the peak center also moves the band range in the same direction.

Of course, all the while paying attention to maintaining the needed suppression.

 

Here is an interesting comparison graph. I have adjusted all of these to fall on OD5 suppression.

Note: the stack using S8612 .5mm thick is simply hard to make that thin, so consider it possible but theoretical.

 

[ulf]

Actually, you could stack U-340 4mm + U-340 3mm together and get a nice 330WB85 filter with MOOB OD4.5. Or you could stack U-340 4mm + S8612 1mm for a 340WB50 with the same MOOB OD. You will need a "real" UV lens (UV-Nikkor, etc.) to realize any potential, otherwise you are going to loose when using such a filter on any 'accidentally' UV capable lens. The parts are available... Or you could get something like this if you want more like a 52mm size with higher UV peak amplitude: https://www.primaluc...ltraviolet.html I think this is the same filter. http://www.savazzi.n...alucelab_u.html

 

I should stay away from UV-pass filters from PrimaLuce!!

 

They did not know anything about the IR suppression of their filters when I asked after getting mine.

The one Enrico got is better then the one I bought.

Mine had an OD of ca 2.5:

[Cadmium]

Thanks for the heads up on that.

That is too bad. Did you return it?

 

There is always 8mm thick U-340. The ring gets pretty deep though. You need a big Pelican case with wheels on it to cart this one around.

I think Jonathan did some various U-340 thickness scans a while back. I can't find that post right now.

 

I will try this on the UV-Nikkor weather and time permitting. This is 8mm, yet unglued, with just a temporary O-ring separation.

It could be a little thinner when glued and installed in a slightly thinner ring, not much though.

[ulf]

Thanks for the heads up on that.

That is too bad. Did you return it?

 

There is always 8mm thick U-340. The ring gets pretty deep though. You need a big Pelican case with wheels on it to cart this one around.

I think Jonathan did some various U-340 thickness scans a while back. I can't find that post right now.

 

I will try this on the UV-Nikkor weather and time permitting. This is 8mm, yet unglued, with just a temporary O-ring separation.

It could be a little thinner when glued and installed in a slightly thinner ring, not much though.

 

No, I kept it.

It was a few years ago when I wasn't that confident about what was needed.

As they do not declare any IR-suppression in their specifications I could not claim that the filter was defect.

It has some artistic value giving some interesting blue tones of the foliage.

I can bring it along and test later when we have green trees and enough UV outdoors again.

 

That thick U-340 would be interesting to try.

I have some Pelican cases it could be carried in.

Is it something you plan to make as a product?

 

It is wise to keep the OD high as the UV/IR-ratio needs to be bigger due to less sensor sensitivity for shorter wavelengths.

[Cadmium]

Does yours say Venus U on it like the current photo shows?

 

No, I just put it together to test now that I can go below 320nm.

[ulf]

Does yours say Venus U on it like the current photo shows?

 

No it say " PrimaLuceLab UV Pass " , not Optolong Venus-U.

They have kept the transmission graph unchanged on their website and still do not declare any IR OD.

The filter I got has a copper coloured coating on one side inly. I think the filter Enrico have has double-sided coatings.

 

The Optolong filter is yet another type with unknown OD in the IR.

It might not be essential for astronomical Venus studies with a high IR suppression, the way we need for our images.

Or if it is problematic there too it might not be that easy to realise that there is an IR-contamination in the Venus image.

[Stefano]

Thanks for the heads up on that.

That is too bad. Did you return it?

 

There is always 8mm thick U-340. The ring gets pretty deep though. You need a big Pelican case with wheels on it to cart this one around.

I think Jonathan did some various U-340 thickness scans a while back. I can't find that post right now.

 

I will try this on the UV-Nikkor weather and time permitting. This is 8mm, yet unglued, with just a temporary O-ring separation.

It could be a little thinner when glued and installed in a slightly thinner ring, not much though.

That’s a brick basically... I guess it’s heavy too... did you make it by stacking two 4 mm pieces?

[Andrea B.]

Stefano: Please let me know that you have read these two posts. Read them all the way thru. Thank you!!!

It is my obligation to ensure that all members understand the dangers of UV.

 

 

[uV SAFETY] UV and Your Eyes :: UV Safety Reference

 

and

 

http://donklipstein.com/xesafe.html

 

 

Not mentioned in the UV Safety topic is the fact that UV-C can damage DNA.