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GM1 IR Performance (poor)

Discussion in 'Panasonic Cameras' started by kwalsh, Feb 27, 2014.

  1. kwalsh

    kwalsh Mu-43 Top Veteran

    775
    Mar 3, 2012
    Baltimore, MD
    Just cross posting from DPR a quick test I did to see how the GM1 does with IR unconverted.

    These were very quick tests. Sorry, no time to do more.

    Tested GM1 with 17/1.8 and R72 filter in daylight. Not practical. At F/1.8 Auto ISO went to 3200 and exposure maxed at 1 second. I did not attempt manual exposure to find the actual exposure required. AF wouldn't function and MF would be very difficult, probably impossible with a F/4.0 zoom. Based on this the GM1 has a strong IR filter and will only be usable unmodified if tripod mounted with very long exposures in bright light. This is pretty typical for Panasonic cameras actually.

    For comparison an E-M5 (which is known to have a weak IR filter) at ISO3200 and F/1.8 gives exposures around 1/50 in the same light with easy AF. So GM1 is probably at least two orders of magnitude "worse" than the E-M5 for unmodified IR use.

    Not specific to the GM1, but since it is kitted with the GM1:

    Also did a very quick check (viewfinder/LCD check only) of the 12-32 on a 720nm modified G1. There were no obvious hot spots to be seen at both wide and small apertures and at 12mm and 32mm. Please note that this was a very quick check for obvious hot spotting. It is quite possible there is a more subtle hot spot that might show up in post processing with increased contrast and a more uniform subject. This means the 12-32 is certainly usable for IR but I'm not sure if it is truly clear of a hot spot or loss of contrast. So it is at least "acceptable" I'd say for IR and with more testing might prove to be great.
     
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  2. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    To make sure I understand, are you saying that the E-M5 without the R72 filter had these exposures?
     
  3. kwalsh

    kwalsh Mu-43 Top Veteran

    775
    Mar 3, 2012
    Baltimore, MD
    Sorry that wasn't clear. No, I meant the E-M5 with the same lens and same R72 filter had those exposures. The exposure without filter was close to sunny F/16 (i.e. 1/3200 at F/16 at ISO 3200). The E-M5 can be used unmodified for IR photography with an R72 filter even handheld when using IBIS, high ISO and a fast lens - and will AF as well - in sunlight. The GM1 (and most other Panasonic cameras) can not. The GM1 passes less than 1% of the IR light the E-M5 does. That's what I meant.
     
  4. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    Okay, got it! Wow - that's an enormous difference. Good to know that the infamous weak IR filter of the E-M5 also makes it usable for handheld IR, without conversion. Thanks.
     
  5. kwalsh

    kwalsh Mu-43 Top Veteran

    775
    Mar 3, 2012
    Baltimore, MD
    Yeah the IR pass for different unmodified cameras with an R72 varies by A LOT!!! Factors of over 100 or even a 1000 aren't unusual. Some of it is how much gets passed through at the longer wavelengths, e.g. what would be the exposure with an 87C (830nm). Some of it is at what wavelength it starts cutting and how sharply it starts cutting. If it cuts at a slightly longer wavelength (say 720 vs 690) then there will be a "window" where the R72 is starting to pass "deep red" light and the camera is still not blocking it entirely. The E-M5 is a particularly weak one. Probably the Leica M8 is one of the few cameras significantly weaker than the E-M5 though there are a fair number of cameras as "leaky" as the E-M5. The beauty with the E-M5 is the good high ISO and IBIS give you the chance at half way decent hand held IR work without modifying.