[Leica] Digital: colour rendition and image quality REPLY

[pdzwig at summaventures.com (Peter Dzwig)]

I have now read all of the mails posted...I  am going to attempt to 
telescope my 
replies into one.

Firstly thanks as ever for being a wonderful resource.

I should have added that I was doing it all in a hurry, as I had been told 
that 
they were being shipped mid-next week, in the event they shipped out on 
Friday - 
less than 24 hours after I finished working. Don't ask about that one!!

I should also have said that the aim was to produce a reference CD not 
actually 
print from them.

Having been brought up with colour rendition in art books as a major subject 
of 
contention. My father worked in the print industry for some forty years to 
support us. As a result I was aware of the difference between image, film 
and 
print quality, but interested by the difficulty the D1 has in areas which I 
thought would have been addressed.

[My father always contended that the best pictures of paintings were in B&W; 
that way you could see the structure of the painting]

WB? - sorry but a D1 doesn't have any. Groan!

Colour card? - yes probably the way I should have gone, but time precluded 
me 
from doing so see above.

Lighting levels? not that constant. We were using daylight away from mid-day 
to 
try and maintain a reasonable level of natural light, but colour variation 
and 
light variation was certainly causing problems; though not the sort that I 
was 
talking about.

Were the pigments metamerismic? Don't know honestly. The issue here seems to 
be 
one of colour rendition. The lighting was fairly constant.

Focus? I tried the pictures in question twice, because I presumed that it 
was 
not me and I have come to the conclusion that it might be a quantisation 
effect. 
What we are talking about here is something akin to clouds of colours 
merging, 
with not a large tonal range between them, but adequate for resolution by 
eye at 
the "film plane".

Thanks again for all your help.

Peter

Jonathan Borden wrote:
> 
> Peter Dzwig wrote:
> 
>> Dear All,
>>
>> I have just spent a few days photographing and recording some of my 
>> late father's paintings before they were sent on semi-permanent loan 
>> to the University of Torun in Poland.
>>
>> I decided for fairly obvious reasons to use my D-1 to take digital 
>> images of the  70-odd paintings which have been shipped. I was 
>> horrified at the variation in colour between the painting itself, what 
>> I saw on the screen and what I actually got on the SD card. Of course 
>> I am aware that my eye and the camera don't have the same response 
>> characteristics; but interestingly I could do little to get the camera 
>> to come close...
>>
>> Is this my D-1, is it common or is there some reasonable explanation?
> 
> 
> Don't be at all surprised. This will *always* be the case whenever you 
> attempt to accurately reproduce colors by digital or film or any other 
> technique.
> 
> You must use a profiled workflow. What you can do is take a shot of an 
> IT8 target with your camera. This will allow you to get an ICC profile 
> for the particular lighting environment w.r.t your camera (you want to 
> use RAW images).
> 
> You need to profile your monitor, printer, inks and paper.
> 
> When done you will get *more* accurate colors, assuming the gamut of 
> your imaging system is adequate to capture the gamut of the paints.
> 
> For example, the gamut of Ektachrome is larger than the gamut of any 
> printing technique -- particularly with bright yellows as I recall.
> 
> 
>>
>> Further, my father painted largely abstract works (you might describe 
>> him as an abstract expressionist, but it's not particularly accurate). 
>> On those where the boundaries between areas of colour were not 
>> distinct the camera appeared to have difficulty in producing a sharp 
>> image. The opposite being true where there were strong boundaries. I 
>> am coming to the conclusion that the image-reconstruction algorithms 
>> taking the output from the chip and building the resultant image in 
>> memory must have been fooled. Any thoughts??
>>
> 
> Perhaps the images are not in focus? Also this is where you really need 
> hi-bit e.g. 16 bits/channel images. Very subtle changes in color can get 
> quantized away with 8 bits/channel.
> 
> Accurate reproduction is harder than you might initially consider.
> 
> Jonathan
> 
> 
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