Latest Attempt with the Omega 293BP10

[Andy Perrin]

Haha, yes, clearly not much light to be gotten, and even less sensor sensitivity (at least with Bayer on there, as Jonathan showed). Clearly you need dabateman's camera and light source, which somehow goes down to ~250nm WITH the Bayer.

[Andrea B.]

As mentioned, I think I was using the wrong lens for the job. The light is traveling down an awfully long tube because of the lack of internal focusing. Double the length of the UV-Nikkor. (No, scratch that, I was wrong.)

---

I made a small force test by stacking the Baader UV/IR-Cut over the 293BP10 and running it for 30 seconds. I did record something but I'll leave it up to you all to decide if it is meaningful. It's very gray. Which seems kind of odd to me, but I haven't really had time to think about it yet.

 

[Andy Perrin]

Andrea, I didn't get that part -- why does it matter which of those, if they are all quartz-fluorite?

[Andrea B.]

I don't know really. It just seemed like the extended CO 105/4.5 is so darned long that I keep thinking it's difficult for the light to get down through it. :rolleyes: :rolleyes: We frazzle ourselves sometimes with weird thinking like that.

 

And I also think I've had much better results in the past with the UV-Nikkor. (Not that those results were all that good.)

[nfoto]

The UV-Nikkor is f/4.5 too, and has no such issues

[Andrea B.]

Right.

 

The CO 105 is 7.5 inches long when extended. The UV-Nikkor is about 6.25" when extended. Hmmm.....nevermind. Like I said, it was hot and sweaty out there.

 

This experiment is so darned frustrating.

[Andrea B.]

Clearly you need dabateman's camera and light source, which somehow goes down to ~250nm WITH the Bayer.

 

Link?

[Andrea B.]

I forgot to mention: I have a 310 nm UV-LED torch now. But I can't tell if it is working.

 

Like, how can you tell if an invisible torch is working or not?

 

I could perhaps try to use this torch in hopes that the right shoulder of the 293bp10 would catch some of the left shoulder of the 310nm light.

[Andy Perrin]

Like how can you tell if an invisible torch is working or not?

Look for fluorescence?

 

Clearly you need dabateman's camera and light source, which somehow goes down to ~250nm WITH the Bayer.

 

Link?

Haven't got one, but you could ask him. I think it's his Olympus that does that?? Can't remember.

 

ETA: Olympus Em1mk1.

https://www.ultravioletphotography.com/content/index.php/topic/3402-60mm-f35-c-mount-uv-lenses-on-ebay/page__view__findpost__p__29155

[dabateman]

Haha, yes, clearly not much light to be gotten, and even less sensor sensitivity (at least with Bayer on there, as Jonathan showed). Clearly you need dabateman's camera and light source, which somehow goes down to ~250nm WITH the Bayer.

 

I have been extremely lucky with the Olympus Em1 mk1.

Here is using a 15W germicidal E26 bulb with the 254nm filter that we got from the Resolve 60mm setup:

https://www.ultravioletphotography.com/content/index.php/topic/3402-60mm-f35-c-mount-uv-lenses-on-ebay/page__view__findpost__p__29008

 

However, this bulb and filter are UVC. Which is very dangerous.

 

Jonathan and I have gotten a 302nm light. This is his spectrum of a 8W unit:

https://www.ultravioletphotography.com/content/index.php/topic/3059-uvp-el-uvl-28-lamp-emission-spectra-with-and-without-filter/page__view__findpost__p__24779

 

This is my image using the same bulb in custom housing. Its a G8T5e bulb that you can buy replacements for:

https://www.ultravioletphotography.com/content/index.php/topic/2580-build-thread-at-home-measurement-of-camera-uv-spectral-response/page__view__findpost__p__27380

 

This is how Jonathan discovered that Canon sensors have an optical low pass filter directly on the sensor coverglass blocking lower UV. The Em1 doesn't have this. I now worry that the newer Olympus cameras may as they have switched to a coverglass with AR coating. The Panasonic MN34230 sensor doesn't have any coatings.

 

[dabateman]

I forgot to mention: I have a 310 nm UV-LED torch now. But I can't tell if it is working.

 

Like, how can you tell if an invisible torch is working or not?

 

I could perhaps try to use this torch in hopes that the right shoulder of the 293bp10 would catch some of the left shoulder of the 310nm light.

Andrea, your 340bp10 may actually catch it. Leds will go longer, not really shorter. Thus why we place U340 glass on the convpy to block any visible.

[Cadmium]

I forgot to mention: I have a 310 nm UV-LED torch now. But I can't tell if it is working.

 

Like, how can you tell if an invisible torch is working or not?

 

I could perhaps try to use this torch in hopes that the right shoulder of the 293bp10 would catch some of the left shoulder of the 310nm light.

 

If you are in a dark room, and you view your 310nm torch with your full spectrum camera + UV-Nikkor, you will see it in the live view.

You will not need any filters for that, if the room is totally dark meaning no UV light either.

 

I still don't understand the As Shot and the RAW composite.

What I would like to see is the RAW file white balanced in NX-D, I don't really care what it looks like as it come from the camera.

[Andrea B.]

I still don't understand the As Shot and the RAW composite.

 

I'm not sure what you aren't understanding? But let me try to answer

 

The As Shot was posted for two reasons.

 

First, it's often useful to compare how a photo looks straight-out-of-camera to how it looks when processing is complete. Such feedback helps develop an intuition so you can make better exposures especially when using a camera which cannot show you precisely what you are going to get. I'm thinking Nikons there which cannot make WB under dark filters. But even cameras which can make WB under unusual filters do not always measure WB accurately. You can get surprises later in the converter. (I showed an example with my Lumix GH1 last summer.) There are other reasons besides the WB issure. But enough.

 

Second, in this particular case, the As Shot view shows that no image formed in Live View.

That was soooo way weird !!!!

 

The Raw Composite is posted because it is again useful to see what is being recorded without all the saturation, white balance and curve tweaks. Again, this helps develop your intuition and basic knowledge.

 

 

---

What I would like to see is the RAW file white balanced in NX-D, I don't really care what it looks like as it come from the camera.

 

The raw file was white balanced in Photo Ninja using a spectralon & color profile preset.

So it will look almost the same if it were WB-ed in NX. But here's one anyway.

 

The towel wrap slipped in this one, so the lighting is quite uneven which made it look like a hot spotty kind of thing in the lower right. The WB was marquee-ed over the spectralon. But in NX2 I can't use the new color profile so the blue might be a bit diff from the other version.

[dabateman]

Andrea,

Put a Baader venus filter over that and see if it looks the same.

[Andy Perrin]

Dabateman, why? Shouldn’t that just cut everything? Baader cuts off at 300 totally, so wouldn’t that just give out of band things?

[dabateman]

Yes,

If she is seeing less than 330nm outside it will be black.

If not she will get the same image. Thats a test I like to do for all my low UV filters.

[Andy Perrin]

Oh, see I thought we had already concluded it was contaminated, so the problem now was how to actually get the 293nm image and block the out of band stuff.

[Andrea B.]

The 293bp10 is not IR-blocked. It was probably made for industrial usage of some kind.

 

Here is a photo with RG 780 x 2 + RG 715 x 2, 4.0 mm total of IR-pass stacked over the 293bp10. Lots of light recorded. Mostly IR I'd say. Of course, now I realize I should have long ago tested this little thing for IR passage.

 

D610 + CO 105/4.5 + sunlight

f/4.5 for 30 seconds at ISO-800

Camera JPG, no edits.

I was aiming at sky on left, some trees on right.

In this particular UV + IR battle, IR wins decisivly!

 

 

And because I'm curious about the raw color, here's the raw composite. The green JPG can be misleading.

Raw composite, pink.