I took a raw cr2 file and changed exposure to -4ev and exported as a 16-bit Tiff. I did the same changing exposure to +4. When I opened up the files in Photoshop where I am able to adjust exposure under the adjustments tab. Brining back the -4 and +4 exports to 0ev and comparing it to the original looks completely different. The -4ev one performed nicely but has a grayish feel to it like the contrast is down. The +4ev on, however, was completely blown out and unable to be recovered. I thought saving as 16bit Tiff would allow for the dynamic range to be preserved so I could recover it?
I did the same only saved -4 and +4 as DNG and this time importing them in Photoshop and adjusting in ACR back to 0ev they were identical to the original 0ev image.
If Tiff is 16-bits why could it not preserve the dynamic range like the DNG could? When I exported the Tiffs did it throw away the information that I was clipping on my histogram? I thought part of the reason we do 16bits is to preserve that info.
I think some of you guys in your replies might have misunderstood the question.
My experience is, if the image is adjusted in ACR so that no clipping of either shadows or highlights is apparent in the histogram, then a 16 bit TIFF conversion of the RAW file will essentially
preserve the full DR and tonality.
This is essentially like asking, is there any advantage in making as many adjustments as possible in ACR before converting to TIFF, or could one do an equally good job making a straight conversion to TIFF with no adjustments other than to ensure there's no clipping of shadows and highlights, then adjust the image in Photoshop to taste?
There may be some advantage in doing as many adjustments as possible in ACR before conversion, but my impressions is they are rather subtle.
One technique that used to be promoted by Adobe to extract the maximum DR from an image, was to create two artificial exposures in ACR of the same image, using say +2 EV for one conversion (to maximise the shadow detail), and -2 EV for the second conversion (to maximise the highlight detail), then combine the two images in Photoshop. I used to employ this technique myself and thought I was getting a substantial improvement.
One day I took the trouble to do a comparison between the 'merged to HDR technique' and a single 16 bit TIFF of the -2EV conversion adjusted in PS using whatever skills I possess.
My impression was, that using the right technique, the 16 bit Tiff conversion at -2EV contained all the image information I needed to get essentially the same degree of DR and tonality that I could get from the other technique of merging the -2EV with the +2EV conversions.
I got the impression that the merging of the two artificial exposures was merely another way of skinning the cat.
However, I don't want to imply that having converted one's RAW images to Tiff, one can then dump the RAW images. If one did that one would then be depriving oneself of the benefits of any future improvements in RAW converters as well as the benefits of existing alternative