3 Replies Latest reply on Dec 11, 2012 9:33 PM by Andrew_Hart

    Ghost Moon objects

    Andrew_Hart Level 2

      This is certainly not strictly on topic for this forum, but given the undeniable expertise of the more-experienced, regular visitors here, especially astrophotographers like Noel Carboni, I was hoping to get some insight into what is happening in the attached photographs. It is because of the availability here of that expertise that I'm asking the Adobe Moderator of this forum not to move this post to some other forum, please?

       

      I have 2 night time, hand-held images of the Moon (captured in Eastern Australia) each of which reveals a coloured, ghost image to the right of the real Moon. The attached are downsized JPEGs extracted from the unedited/unprocessed RAWs. The original, full-sized RAW images display a certain amount of camera shake, the 2nd (.CR2 - most recent) more than the 1st (.CRW). I think, but can't be positive, that White Balance was set to Auto for eash image.

       

      The 1st image (.CRW) was taken in January 2004 on a Canon EOS 300D fitted with the bundled, el-cheapo 18-55mm zoom lens set at 55mm (88mm equivalent for a 35mm full frame camera). The exposure was made in Program mode (effectively, fully automatic) for half a second at ISO 400 and f/5.6. The bright spot above the ghost moon is not a star but rather Jupiter, the very conjunction of which with the Moon being the main reason I took the photograph. Close inspection at 100% magnification of Jupiter in the original RAW file reveals that it is not ghosted.

       

      The 2nd image (.CR2) was taken in September 2012 on a Canon EOS 5D Mark II fitted with a Canon EF 50mm f/1.4 USM lens. The exposure was made in Bulb mode for 1 second at ISO 1600 and f/4.

       

      Can anyone explain how or why the coloured, ghost images of the Moon are being generated ?

       

      I strongly suspect that the camera shake may well be the, or at least a contributing, cause, but I don't understand either why it would lead to the ghost image results or why there is a change in colour of the ghosts to green and blue respectively from the white, real Moon

      colour.

       

      CRW_0007_Jan2004.jpg

      CR2_0837_Sept2012.jpg

        • 1. Re: Ghost Moon objects
          Robert Shomler Level 4

          Could be generated by the outer lens glass surface or front of lens (uv) filter.  I've seen similar ghosting in photographing theatre stage, where there is a strong light source in contrast with a relatively dark background.  In theatre, changing the angle of camera to stage can move or eliminate the ghost.

           

          Way to test. Try some moon in dark sky photos where you change the relative location of moon in your frame - off center.

           

          Re color, the appearance of moon being white is likely blown highlights (overexposure) where all channels are driven to 255.  A lesser exposure might reveal uneven color channel levels in the moon, as you can see in the cloud (2004 photo).

          • 2. Re: Ghost Moon objects
            ssprengel Adobe Community Professional & MVP

            Remove the UV filter from the front of your lens camera.  The green ghost is the reflection of the moon off the relatively green sensor (twice as many green photosites as red or blue) that goes back up to the UV filter glass, then back down to the sensor.  The surfaces of your camera lenses are curved so don’t usually generate such recognizable reflections but the flat surface of your UV filter does.  The UV glass only reflects a small fraction of the light, but when the light-source is very overexposed this reflection is bright enough to see.    If you use M-mode and dial back the exposure enough to to see surface detail on the moon the ghost might be dim enough to not be noticeable but it’s usually better to remove the UV filter, anyway, unless you have a good reason to use it and understand about not overexposing light sources when it’s on.

            • 3. Re: Ghost Moon objects
              Andrew_Hart Level 2

              Robert Shomler and ssprengel,

               

              Your suggestions about the UV filter (which I did indeed have attached to both lenses - well guessed!) make much more sense than my camera shake theory. Thank you.

              I'll try out this UV filter theory as soon as a suitably fullish Moon is again visible in my night sky.

               

              I'll also try out your off-centre theory, Robert. Re the colour changes and blown highlights, I'll be more careful with the exposure in the next experiment. Interestingly, the colour changes are in each case (between photographs) different - green in 2004 and blue in 2012. But admittedly I was using different cameras and lenses and possibly even different White Balances.

               

              To this forum's Adobe Moderator:

               

              Thank you for leaving this thread in place.