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UV/IR response for G1/GH1/GF1 ??

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brianc1959

New member
I just got a m4/3 to Nikon F adapter for my GF1, and discovered that both UV and IR are 14-15 stops less responsive (using B+W 093 and Baader U, respectively) than the VIS band when using a broadband lens with flat transmission from UV-IR. I assume that replacing the filter pack with a broadband transparent glass will improve the IR response drastically, but what about UV? Hoping Vivek or someone else might know. Also, does anybody know the thicknesses of the filter pack and the sensor coverglass?
 
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Vivek

Guest
Brian, First of all, your tests confirm my findings on UV and IR response of an unmodified G1.:)

I hacked my first G1 for this very purpose. Unfortunately, I did a silly mistake and wrecked the SD card slot (which is flimsier than any cell phone SD card slot).

I did remove the UV/IR/AA filter stack. I can see in IR very well.

The modified G1 cam:

IR response is about +2 stops (Hoya R72) responsive than the stock G1 (ie., relative to the Visible reading) about -1 with a Heliopan R780 and about -3~4 stops with a Heliopan R1000 filter.

UV, I am having real trouble with judging the response. There is clearly UV response but it appears (need to verify this) to be less than the corresponding Olympus E-410.

The NMOS sensor (on a flex board) has a permanent glass cover, the filter stack goes on top and then there is a thin protective glass cover that also serves as the ultrasound dust shaker.

I have to figure out if the flex board cover glass (that would be bad) cuts UV or the Ultrasound shaker cover glass that cuts UV.

Self modification of G1 (or GF-1), as I find, is a bit too much to chew for my abilities.:banghead:

I have another G1 purchased specifically for this purpose (another kind gesture from Robert Campbell here)....:eek:
 
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Vivek

Guest
brianc1959 said:
Also, does anybody know the thicknesses of the filter pack and the sensor coverglass?
Click to expand...

I missed that. I have 2 AA/UV/IR filter stacks (one was a kind gift from a member Cindy). I have to buy another Vernier calipers to make the measurements (current one is broken). I can send one to you.

The cover glass is very thin. Definitely less than 1mm thick. It is coated on both sides.
 
pellicle

pellicle

New member
Coincidentially we were testing exactly this with a G1 and a 5DII at work using a UV pass filter and a UV lamp. We found similarly but also found that lens seems to make a very significant difference too. We would like to try testing with my friends Takumar ... pitty he's in Canada
 
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Vivek

Guest
Pellicle, 5DII will be a waste of efforts (for UV in particular and there will be very little IR response).

You will need the first version 35mm f/3.5 Takumar for UV.
 
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