Resolution: Epson color inks Vs K7 Piezograph

[sanking]

I recently purchased a Piezograph K7 Selenium set and plan to change over my Epson 7600 soon from the Epson color inks to the Piezography set. One of the main reasons I purchased the Piezography set was to set up a dedicated printer for making digital negatives in anticipation that it would give better resolution than the Epson color inks. As we know, the maximum resolution of Epson printers is about 7 lp/mm, based on the fact that there is no improvement in sharpness in printing at file resolution of more than 360 ppi.
Before I make the change over I would like to print a resolution chart with the Epson color inks that I can later print with the Piezography set to compare results.

My question is, can someone point me to a good resolution chart for this purpose that I can download to use for the test?

Sandy King

[ric_kb]

these don't download, but are the "standard" charts mentioned often, used rarely...

http://www.edmundoptics.com/onlineca...productid=1790

this is a link to a PS version

http://photo.net/learn/optics/USAF1951.ps

richard.

[Ron Marshall]

Scroll down for the chart and instructions for use and interpretation:

http://www.clarkvision.com/articles/...ppi/index.html

[sanking]

Hi Ron and Richard,

Thanks for the links. I found a couple of useful test charts and am now printing my test prints with the Epson UC ink set.

Sandy

[Kirk Gittings]

FWIW, I recently (like three weeks ago) had a large digital print made from a scanned 4x5 b&w negative for a museum show. The service I use for large images runs both Epson and Piezography inks so I had identical prints made. I had seen first hand the very impressive resolution comparison tests that Cone had done and was curious to see if it was noticeable in my actual prints. In this case it wasn't. However this image did not have allot of fine detail. While I greatly preferred the tonalities of the Piezography inks, there was no apparent resolution advantage with this image that was visible even on very close inspection with reading glasses.

[sanking]

FWIW, I recently (like three weeks ago) had a large digital print made from a scanned 4x5 b&w negative for a museum show. The service I use for large images runs both Epson and Piezography inks so I had identical prints made. I had seen first hand the very impressive resolution comparison tests that Cone had done and was curious to see if it was noticeable in my actual prints. In this case it wasn't. However this image did not have allot of fine detail. While I greatly preferred the tonalities of the Piezography inks, there was no apparent resolution advantage with this image that was visible even on very close inspection with reading glasses.

You make a good point about the limitation of the original. The limit to resolution will always be the weakest link in the chain. In this case the fact that your image did not have a lot of fine detail would mask any difference between Epson and Piezography inks, if indeed they exist.

I had a similar experience in printing some of the resolution targets I downloaded from the net. It at first escaped my sense of logic that they were all file sized at 300 dpi, which essentially makes them useless for my purpose since even the Epsons inks are capable of ar least 360 dpi (7 lp/mm) of real resolution.

Fortunately one of the links (http://photo.net/learn/optics/USAF1951.ps) provided a file that I was able to rasterize to increase effective resolution so I am printing the tests again with the Epson UC ink set.

Sandy

[sanking]

Here is my first report on resolution with the Epson 7600. The tests were made printing with QTR, the file set to 1440 ppi, 720 ppi and 360 ppi. I used the Enhanced Matte Cool profile from the UC list of profiles, and set the printer to 2880 dpi and bi-directional printing.

Results were something of a surprise. From habit I have always set my file size at 720 at the print size but many of my friends who use Epson printers have told me that there is no difference in image quality with the file set at 360 ppi or 720 ppi.

That turned out to be wrong in my tests. Results with the file set at 360 ppi indicate a resolution of 7 lp/mm, just what I expected. However, with the file set at 720 ppi there was a significant increase in resolution to nearly 12 lp/mm. No additional improvement was seen with the file size at 1440 ppi.

In a few days I will change the printer over to the K7 Piezography ink set and repeat the tests.

Sandy

[Kirk Gittings]

Interesting, I look forward to the rest of your tests.

Fortunately one of the links (http://photo.net/learn/optics/USAF1951.ps) provided a file that I was able to rasterize to increase effective resolution so I am printing the tests again with the Epson UC ink set.

How does rasterizing increase effective resolution of the target?

[paulr]

Results with the file set at 360 ppi indicate a resolution of 7 lp/mm, just what I expected. However, with the file set at 720 ppi there was a significant increase in resolution to nearly 12 lp/mm. No additional improvement was seen with the file size at 1440 ppi.

Were there any differences that would be visible in a print, looked at without magnification?

I print at 720, just for the hell of it ... at least if the file has that much resolution in the first place. But the only differences I've been able to see have been in aliasing of certain slightly diagonal lines. Sometimes this is barely visible at 360 but never at 720.

My experiments have been on photorag, which may also be a limiting factor ... not sure.

[sanking]

Interesting, I look forward to the rest of your tests.



How does rasterizing increase effective resolution of the target?

Kirk,

Perhaps it did not. Looking at the original file again in Preview it looks like the resolution might have been there to begin with. However, the first time I opened it in Photoshop the resolution was quite low. Then I opened it again at the original file size, but at 5000 ppi, and I got a message, "Rasterization" in process, and it took a long time for the file to open. The fact that this is a high contrast resolution target with black lines on white background may have something with how it can open at different resolutions. I don't know for sure, perhaps you could download the file and see what is going on.

Sandy