ProfHankD wrote:
E Dinkla wrote:
ProfHankD wrote:
JonesLongShot wrote:
The most important material is the focusing substrate as it defines the look and detail of the final image more than anything. I tried lots of different papers and things like white polystyrene and bead blasted aluminum. In the end I liked really fine paper the best. This part still needs lots of experimentation. The finer the surface structure, and the more reflective the material, the more it approaches an actual mirror and that completely destroys the whole thing.
Ordinary white paper was what I ended-up using in the FourSee TDCI Multi-Camera . The best image quality was actually using an Illford inkjet paper, except it was glossy enough to give some reflections.
You might consider Epson Proofing White SemiMatte next time. An RC paper without OBA content but with very high white reflectance, and a more continuous reflection along the visible spectrum. There are smooth matte inkjet papers that come close to that reflectance value without the glossy issues. With and without OBA content.
I think the Ilford paper was what you call N Gal. Prestige Smooth Gloss RC 310, which is flatter in response than most cheap papers (Sam's Club used to sell it dirt cheap), but I definitely see what you mean about the Epson Proofing White Semimatte RC 256. I only tried the dozen or so different types of papers that I happened to have on hand. Resolution, dynamic range, and lack of texture were higher priorities than spectral evenness in my choice, but in the end, avoiding specular reflections became the deciding factor. If I was ever to use this type of system for multispectral imaging, I think your database would be the thing to look at, and I think it definitely is the right way to think about material choice for a large obscura's front-projection screen.
Or select another inkjet paper from the data shown in SpectrumViz. For that tool I measured more than 700 inkjet papers + some other paper types. https://www.pigment-print.com/spectralplots/spectrumviz_1.htm Free download
Now that is an impressive bit of work!
Lexington, KY, where I live, is home to the old IBM printer division which was spun off as Lexmark. They're only a shadow now of what they once were, but they had an outstanding group of folks working on print image quality, and I don't think I've seen anything like your database since working with them years ago. Extra impressive that "a guy running a small print shop" would go to a similar level of detail in such characterizations as a research lab in a company the size Lexmark was...
Not the Gloss but I still have a roll of the Ilford N Gal Prestige Smooth Pearl version Made in Switzerland.
Added here a screengrab of SpectrumViz, Red a pure OBA component, Yellow your paper, Green is Hahnemuehle PhotoRag Ultra Smooth that is matte and has very little texture but a small amount of OBA, the Brown and Blue represent a Felix Schoeller made paper sold by more companies, no OBA content but slightly textured. As a reflection paper in a camera the chances that UV light will enter are minimal but that will reduce the Lab L value and shift the reflection to a warmer image when the paper depends more on OBA content.
Over time most OBA' s also loose their fluorescence effect due to oxidation and in worst case they add a yellow stain beyond the original natural paper color. Epson changed its Archival Matte paper name as it became clear the white color was not "Archival", whatever that means. https://lists.apple.com/archives/colorsync-users/2019/Jun/msg00056.html
I have used the Felix Schoeller paper as a diffuse reflection material in lightboxes, it lasts long if applied with an acid free glue.
Yes, it has been a lot of work and should be updated again as new papers appeared and specifications of older papers changed over time. In general the better inkjet paper qualities improved on all fronts including the white reflectance and lightfastness. I used to go to the Photokina and came back with bags full of papers, not the camera brochures but inkjet paper samples. Due to my age and Covid that has not been the case for some years.
There used to be an interactive application on the RIT website where you could get visual information of the texture, specular reflection character, color, etc of a print/paper technology next to some measurement data. Few paper types though. That was what I had in mind to make for inkjet papers but even measuring Lab values and spectral distribution of the white reflection was a major task. Inkjet Dmax measurement could have been added but so many different inkjet inks and inkjet technologies to cover. Gloss differential (bronzing) visualised by a stepwedge B&W inkjet print on glossy paper . Thought of a customised flatbed scanner to do that, scanning at a fixed angle with a fixed point light source on the carriage.
The RIT webpages were always entertaining, especially the Andrew Davidhazy experiments. At least they can be found somewhere else.
Off Topic meanwhile, I know.
Met vriendelijke groet, Ernst
No photographer's gear list is complete without the printer mentioned !
