Introduction Greynomad (ian)

[colinbm]

In my graphs they are both 0.4 to 1.15 uM

 

I have no idea what the Kodak 301a is ?

[Greynomad]

Hi Da Bateman

I did a quick and dirty test of olympus camera sensitivity to UV light using a Convoy s2 torch with ZB2 filter set up at ISO 200 and a fixed distance using the Olympus 30mm f3.5 lens at f3.5.

Results.EM-10 1/25, EP-3 1/125, epl-5 1/200, Lumix g2 1/250, EM-5 mk 2 1/400, EM1 mk1 1/640 .

 

I did take some images outside but it was late afternoon and the sun very low, long exposures,will try tomorrow with a high sun. Do you set a custom white balance?

Is the sigma 30mm f2.8 better than the olympus 30mm f3.5 with regards to uv transmission?

[JMC]

David, to me those 2 graphs look very different. 600nm, 7-74 is up around 80%, 7-75 is around 50%, 1000nm, 7-74 about 20%, and 7-75 is 0. But yes I do agree that I don't know what the difference between transmittance and external transmittance is.

[Greynomad]

Hi Da Bateman

I did a quick and dirty test of olympus camera sensitivity to UV light using a Convoy s2 torch with ZB2 filter set up at ISO 200 and a fixed distance using the Olympus 30mm f3.5 lens at f3.5.

Results.

EM-10 1/25

EP-3 1/125

EPL-5 1/200

Lumix g2 1/250

EM-5 mk2 1/400

EM1 mk 1 1/640

 

Is the UV trasmission of the Sigma 30mm f2.8 better than the olympus 30mm f3.5?

Do you do a custom white balance as in IR photography?

Did try some outside shots but late afternoon resulting in long exposures, will try tomorrow during middle of the day.

[dabateman]

Ian,

This was one of my UV reflectance tests using a full spectrum converted EM1mk1 camera:

https://www.ultravioletphotography.com/content/index.php/topic/3540-canon-40mm-f28-pancake-is-370nm-uv-fast-on-m43rds/page__hl__%2Bolympus+%2B30mm__fromsearch__1

 

https://www.ultravioletphotography.com/content/index.php/topic/3321-comparison-olympus-30mm-macro-vs-sigma-30mm-art-vs-olympus-14-42r2-in-uv/page__hl__%2Bolympus+%2B30mm__fromsearch__1

 

This plots might be confusing. But my Sigma Art 30mm f2.8 lens cuts off at about 355nm. I don't have the Olympus 30mm f3.5 macro posted here, but remember it to be about 365 or 370nm.

 

https://www.ultravioletphotography.com/content/index.php/topic/3897-spectroscopy-fun-with-some-lens-tests/

 

Yes create a custom WB setting, I use WB1 for a UV filter and WB4 for IR filter. If you don't have a block of PTFE, then get some plumbing tape (PTFE tape) and wrap it 5 times around a business card. Use that to snap a custom WB setting.

 

You Panasonic G2 exposure settings surprised me. I have generally found Panasonic to block UV and Olympus cameras to be UV leaky. Interesting, I have been craving a Panasonic G9 body and maybe it too might be UV leaky.

[Cadmium]

The two graphs above that Colin posted from the book are a little different. The example using plate glass doesn't remove the upper IR.

Note that the first graph has the 301 coating on a plate glass substrate, and the second graph has the 301 coating on 'heat absorbing glass' substrate (Schott KG type glass).

The heat absorbing glass removes the upper IR as well.

The 301 coating on its own transmits a lot of IR around 900nm and up.

Neither of those graphs are good for Red/IR suppression, they don't cover the range and I doubt they have much OD to adequately suppress any U type filter for UV-only (UV-pass) photos,

if in fact that is the reason for talking about these 301 filters here. 301 filters will not work for that idea at all, they are worse than even BG38 (don't ever use that for UV-only stacks).

[dabateman]

 

I have no idea what the Kodak 301a is ?

 

Didn't Kodak make those for the Canadian market. I have the 301 filter eh.

 

The New York ones might be A301, as in eh, thats a 301 filter.

 

[Greynomad]

DaBateman

I have a Panasonic G9 , but both my batteries are flat at the moment so as soon as charged I will test it for you.

It looks like I will have to buy an S8612 2mm filter.

Tried live composition, like it did UV reflectance seems to work well. Will do some further testing with UVIVF after dark tonight.

going through my filters I have a UV IR block filter unmarked but in a Hoya case appears to block both UV and IR will give that a try.

If you where to convert an Olympus camera for UV reflectance which would you prefer EM-1 MK1, EM-5 MK1 or EM-5 MK 2.

[dabateman]

Yes please if possible take an image of a dandelion or some flower, using your UV flashlight in the dark with the U360 filter on the Olympus 30mm Macro lens with both the Em5mk2 and the G9.

Please post the images. That should let me know how leaky the G9 is, compared to a reference I have.

 

About conversion is tricky. I got Kolari vision to full spectrum converted my Em1 mk1 with fused silica on the sensor. Its amazingly sensitive to even 300nm. That seems extremely difficult with most cameras. I haven't gotten my Em5mk2 converted yet. I am not sure if it will be as sensitive to UVB with its Sony IMX109 sensor as the Panasonic MN34230 sensor in the EM1mk1. But the Em1mk1 has issues. After conversion, the rear dial stopped responding. I need the grip to get it to work. Also the electronic shutter is limited to 1/8 seconds, which does have focus stacking limits.

 

If you don't see yourself playing with dangerous UVb lights, then I would go for the Em5mk2. If you want to push the boundaries into deep imaging, then the Em1mk1 might be better.

[SteveE]

The electronic shutter on my unmodified (as yet) Em5 mk2 goes to 60 seconds. I don't have a mk1, but the mk2 blurbs mention the new silent shutter mode. Also the mk2 has a stop better image stabilization than the mk1.