[Radiance-general] printing floating point images

[Jack de Valpine]

Jelle,

Like Mark I will add in what I know and what we have done in the past to 
get the best quality prints possible (for a reasonable cost).

In general you need to print to a print device that goes direct rgb. I 
think that a fair amount of progress has been made for printing digital 
images (rgb) direct to photographic quality paper (paper makes a huge 
difference). We have had good success with two devices and one service:

   1. Lambda Printer - this is a big fancy printer that only a large
      service bureau would have (I think that the cost around $500,000
      US). They can print to very large paper sizes (photo paper). I do
      not remember what the resolution is, although we found that you
      could have quite good image quality even at 100dpi. Cost - expensive.
   2. Kodak Pegasus Printer- cannot print as large as the lambda but is
      direct to photo paper. Is more sensitive to image resolution, I
      think they prefer 250dpi. Cost - medium to expensive.
   3. Online Service Bureaus - we have also used Ofoto on occasion.
      Again the print is direct to photo paper. Cost - INEXPENSIVE!

Depending on the device selected, I expect that one could also prepare 
some kind of calibration to make sure the images are calibrated to the 
device (which means that you have to make sure your other output devices 
such as monitors are correctly calibrated as well).

Of course none of this answers your question about bit depth. I guess 
one question to ask is how much is needed to achieve what you want. 
Alternatively, another way to look at it is to learn what professional 
photographers using high end digital cameras do for printing, I can only 
imagine that this could get quite expensive however.

-Jack

Mark Stock wrote:

>Jelle,
>
>This is a very interesting question, and one in which I have an
>interest in following. I'll share with you my limited knowledge.
>
>It has been my knowledge from speaking and reading about display
>devices (mainly reflective print and transparency film) that film
>can record a greater range of brightnesses, allowing it greater
>bit depth. Print is hindered by its reflective nature, and the
>upper and lower bounds of reflectivity (users of Radiance are
>more aware than most that what is normally percieved as white is
>probably no more than 70-80% reflective).
>
>I have been assured by professional digital printers that a
>good 8-bit-per-channel image gets printed just as well as an
>image with grater depth. I may have even been told that the
>rasterizer upgrades the bit depth as it upsamples the image.
>I can't confirm that, though.
>
>I usually print on a Lightjet 5000. I use ra_tiff to convert my
>.pic into a 16-bit-per-channel TIFF, then I use Cinepaint on
>Linux to do final adjustments, outputting to an 8bpc TIFF.
>
>Mark
>
>On Wed, 1 Dec 2004, Jelle Feringa // EZCT / Paris wrote:
>
>  
>
>>I wonder if anyone on this list has experience in printing 32 bit floating
>>point images (radiance pics preferably)? Some years ago I had some vibrant
>>discussion with Iebele Abel on this matter. I find it a rather frustrating
>>idea to thrash spending much time and effort getting a physically accurate
>>rendered image, and thrashing a tremendous amount of image fidelity to get
>>the image printed, there where it counts most. I've been able to get 16-bit
>>data images, but what I'm interested in is getting the full scope.
>>The relevant question indeed is what would be limiting output quality.
>>Its quite likely paper of photographic means are only able to output so many
>>colours. I refer to physical limitations, rather than those implied by a
>>data format.
>>
>>It seems that film industry has successfully overcome getting lack of colour
>>fidelity, also thank to the openEXR format (basically a clumsy rip-off of
>>the radiance image format??) but mostly by actually being able to output the
>>full scope of the data.
>>
>>So how would I get this done in print, its quite a concern to me.
>>
>>Best,
>>
>>Jelle.
>>
>>
>>
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>>
>>    
>>
>
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>  
>

-- 
#	John E. de Valpine
#	president
#
#	visarc incorporated
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