Build thread - at home measurement of camera UV spectral response

[JMC]

New data May 7th 2019 - Sparticle test of Multispectral EOS 5DSR with OLPF filter removed from sensor

 

Now the 2nd OLPF has been removed from the front of the sensor, from my converted EOS 5DSR, I have repeated the Sparticle test from post #87 above.

 

I took my Multispectral 5DSR and Rayfact 105mm lens (f5.6, ISO400) no filters on the lens, and took a sequence of shots between 1/4s and 8s exposure. Sparticle pointed at blue sky, but away from the sun. Images imported into RawDigger as RAW composites then screenshotted.

 

This is what they look like as RAW composites in RawDigger (top row L to R, 303nm, 321nm, 341nm, middle row L to R, 355nm, 364nm, 382nm, bottom row L to R, 396nm, 404nm, 405nm).

 

1/4s exposure

 

1/2s exposure

 

1s exposure

 

2s exposure

 

4s exposure

 

8s exposure

 

Removal of the second OLPF has allowed much more light through the 341nm and 321nm filters (top row, middle and right). Still can't see much at 303nm, but then there is virtually none in sunlight anyway, so I wouldn't be expecting much there with this test.

[dabateman]

Jonathan,

Try placing this infront of your 302nm bulb in your UVL-28. Should get the full broad range there. Especially if both bulbs are on.

 

[JMC]

Jonathan,

Try placing this infront of your 302nm bulb in your UVL-28. Should get the full broad range there. Especially if both bulbs are on.

On the list of things to do David.

[JMC]

Sparticle image using the 302nm UVP lamp

 

The spectra for this 302nm fluorescent lamp is given here;

 

https://www.ultravio...dpost__p__24779

 

I have 2 of these mounted in a UVP light source, and have taken some Sparticle images with them. Multispectral EOS 5DSR, Rayfact 105mm UV lens, f5.6, ISO400. No filtration on the lens. Images captured as RAW, and imported into Rawdigger as RAW composite files. Then a screenshot taken and cropped in photoshop.

 

2s exposure

 

4s exposure

 

The filters are arranged as follows - (top row L to R, 303nm, 321nm, 341nm, middle row L to R, 355nm, 364nm, 382nm, bottom row L to R, 396nm, 404nm, 405nm).

 

The way the intensity of the 302nm light source drops with increasing wavelength, nicely offsets the way in which the camera sensitivity drops with decreasing wavelength, so as a result a wide range of the filters end up being reasonably exposed in the images. This might be a nice light source to try and get multiple UV 'colours' in an image.

[dabateman]

That looks great. 2 to 4 second exposure at 302nm, amazing. I just recently got a 302nm bulb. Still waiting for a fixture to place it in, but hopefully arrive tomorrow.

Didn't know how cheap they could be. It will be hard to figure out how to work with a 12 inch linear bulb though. I like standard E26/E27 bulbs in desk lamps as they are easy to control.

Yes even with the Uvb exotrra type bulbs the exposure is almost the same across the wavelengths, from 313nm, 365nm, 390nm and IR. The visible is stronger, but composed of more wavelengths.

[dabateman]

Well I got my 302nm bulb working in an under the counter fixture. It is very dangerous. The 300nm and even 280nm light coming off it is strong.

 

Here is a flower image taken with my 300bp10 filter, ISO 800, F8, 60 seconds with the UAT:

 

I think I am just seeing 280nm with the this light as well. I get some reflections off the same flower, here is an image in red to make out more clearly the reflections. ISO 1600, F8, 60 seconds with UAT:

 

I will stack this with other UV bandpass filters, 313bp25, 335bp10, 340bp10, 370bp15 and 390bp25, to ensure that this is only in the 280 area and not leak within an other UV band. I have it stacked with the 330WB80 improved, which I am confident lets in about 270 to 390nm, and is actually well IR blocked.

 

This also possibly confirms that a WG280 glass on the camera is just as good as fused silica, as the camera sensitivity limit does seem to be 280nm.

[JMC]

Very cool David.

[dabateman]

I liked this 8W one so much, that I have ordered a 15W one. I have been missing out with proper lighting. Going from minutes to seconds is much better and its cool for the flowers. The mercury vapour lamps I have are just too hot. Also the 313nm peak off this is amazing. I can now use live view to focus. 313nm is ISO 200, 8seconds. With a ExoTerra UVb bulb I was routinely getting ISO 800 at 30seconds. So as I said these are very dangerous. I have used gel docks a lot in the past and have burned my wrists twice. So I know to be careful.