Banding - is it because of the preview image stored in RAW?

[ptimlin]

Hopefully someone can set my mind at ease about a used lens I bought. I took a photo walk today at lunch to test it out and shot maybe 20 photos. When I got home I used GC to download them off the card and look at them via the GC browser A few of them where shot with a lot of blue sky in the upper part of the shots and looking closely I see the entire sky is made up of bands arcing through the photo with digital artifacts in them. I then pull them up on the camera and I can see them on the LCD on my camera as well. Crap! Even when I did the full-screen view in GC I see the bands.But opening them up with preview, the banding was gone and everything looked great. It then hit me. I bet the weird banding only exists in the little JPG image embedded in the RAW file (Olympus by the way). Sure enough, when I open them in GC in edit mode, the banding is gone.So I think everything is ok, my camera made some crappy JPG preview icon in the RAW and it just so happens my camera and GC both show that JPG rather than the RAW file. But thought I would post here to see if anyone else has run across this strangeness before.Patrick

[dsample1957]

I suspect that in order to save more space the previews are saved using 16 bit colour, instead of 24. Normally this isn't really obvious when you look at an image, but one place it can really show up is when you have large areas that are not quite all the same colour, with a subtle gradient across them, such as in a nice blue sky.

[thorstenlemke]

Dear Patrick,do you let GraphicConverter calcualte a high quality preview or do you use only the low res preview?Thorsten Hopefully someone can set my mind at ease about a used lens I bought. I took a photo walk today at lunch to test it out and shot maybe 20 photos. When I got home I used GC to download them off the card and look at them via the GC browser A few of them where shot with a lot of blue sky in the upper part of the shots and looking closely I see the entire sky is made up of bands arcing through the photo with digital artifacts in them. I then pull them up on the camera and I can see them on the LCD on my camera as well. Crap! Even when I did the full-screen view in GC I see the bands.But opening them up with preview, the banding was gone and everything looked great. It then hit me. I bet the weird banding only exists in the little JPG image embedded in the RAW file (Olympus by the way). Sure enough, when I open them in GC in edit mode, the banding is gone.So I think everything is ok, my camera made some crappy JPG preview icon in the RAW and it just so happens my camera and GC both show that JPG rather than the RAW file. But thought I would post here to see if anyone else has run across this strangeness before.

[ptimlin]

Hi Thorsten,Sorry for the delay. Just getting around to this again. Anyway, took me a while to find it but in my preferences I have the High Quality option picked under Browser -> General.Patrick

[thorstenlemke]

Dear Patrick,please e-mail a problem image file zipped to lemke@lemkesoft.deThorsten Hi Thorsten,Sorry for the delay. Just getting around to this again. Anyway, took me a while to find it but in my preferences I have the High Quality option picked under Browser -> General.Patrick

[ptimlin]

Hi Thorsten,I will send it to you so you can see it first hand, but I am thinking it is not a problem with GC but instead just a poor quality JPG preview. As I mentioned in my first post, I found that when I view the same photo when it was still in my camera on its back LCD screen I saw the exact same banding and I think GC is just showing the same low quality JPG.Photo coming your way in a minute.Patrick

[thorstenlemke]

Dear Patrick,ah - that is only the low resolution preview from the camera. You will get the high quality preview only after the import in the file system.Thorsten Hi Thorsten,I will send it to you so you can see it first hand, but I am thinking it is not a problem with GC but instead just a poor quality JPG preview. As I mentioned in my first post, I found that when I view the same photo when it was still in my camera on its back LCD screen I saw the exact same banding and I think GC is just showing the same low quality JPG.Photo coming your way in a minute.Patrick