Archived posting to the Leica Users Group, 2003/07/31
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Hi To all, While I certainly agree with Mark about high contrast being an issue with the D100 or any other digital camera I can't agree with the following: " There is no shoulder, and the slope of the curve is alway increasing. The metered exposure gives an output of about 97, which is below what you would expect (128). Without adjustment in Photoshop, the images coming out of the camera have very dark shadows, muddy midtones, and highlights with excessive contrast, just as the characteristic curve would predict." Without a thorough knowledge of how he actually plotted his characteristic curve, or the workflow that was used to arrive at the image, it is hard to dispute what he says, however, if you measure a target such as the DC ColorChecker and properly plot the tone reproduction of the camera, I don't believe that you will see the same results. The camera has a small toe and it has a shoulder. The reproduction gamma is set so that the midtone reproduction gamma is somewhat above 1.2 which is the assumption that nearly all consumer camera manufacturers build into the camera. This is based upon the viewing conditions for most electronic displays. It's important to note that the camera output has been corrected for viewing on a display system with an assumed gamma of 2.2 in a dark environment. An 18% grey in a gamma 2.2 corrected, 8 bit system is representated nominally at level of 118, not 128 as stated. As I stated, there is normally a slight increse in the system gamma to 1.2 . An 18% grey value would be represented by a numerical level of 100 in such a system. Marks results seem to indicate a value of 97 so I think we are on the same page, but we are interpreting it differently. For users of Nikon cameras, it is highly recommended that you store your data in their proprietary NEF format. This format allows for a great deal of post correction (except for over exposure). Archiving in NEF format will allow for improved transformations to the latest ICC specification when all the manufacturers of Color management software finally catch up. My experience with Digital Cameras has been that they require a certain amount of time to learn. It IS different than film. On the other hand, I certainly have had much fewer problems taking well formed digital images to paper and digital display, than scanning transparency media to the same formats. On the other hand, there is no doubt that the projected slide looks far better than the repoduced prints. In my own experience, when the desired output is going to be primarily displayed on digital media, I start with a digital image or a scanned negative. The negative provides a very easy image to scan and generally reproduces with minimum fuss. I have found in my own work that the increased contrast of the transparency media is more difficult to correct. If I was going to Alaska, I would fill my Nikon with Ektachrome 100GX or Provia 100f and I would put Kodak Portra 160NC in the Leica :) , just like I did when I went to Utah. In low contrast situations, I used the transparency camera and in most of the outdoor high contrast shots, I used the negative. The dynamic range, particularly in the case of over exposure is spectacular. It was the only camera (Leica + negative film) that gave great results in the slot canyons. In any event, just take good pictures and enjoy your vacation. If you do take that Digital Nikon, underexpose a bit, store those images as NEF, there will be better rendering solutions in the upcoming year. Tom Lianza Technical Director Sequel Imaging Inc.- A GretagMacbeth Company 25 Nashua Rd. Londonderry, NH 03053 - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html