Hi Kok Leong, I've been following your web site and the Epson digest for a while now trying to decide which printer to buy. I finally decided on the 900 which I just got a few days ago. I liked the dotty spotty article following which I decided to observe my 900's output on an Olympus microscope with an attached MTI 3CCD camera.. I am inquisitive by natureand like to compare. I have on hand demo prints on Epson photo paper of an Epson 640, Photo 700 and HP 2000C. I would rather have custom prints though since I don't know what settings were used (I just hit the print demo button).

Doing it all at the same magnification is no problem. (I can go to a higher mag but that does introduce other difficulties) The next time I use the scope, I am going to put in a unit of measurement of some sort so we can find out the exact size of the dots. Either a defraction gratting or an electron microscopy grid that I know the specs of. Ending the debate on dot size once and for all should not be a problem! (at least for the papers we test on)

Paper - I like the new Epson photo paper (at least for comparing Epsons).If we add other printers to the mix, we should probably use their recommended premium paper to be fair plus the Epson photo paper.
Lighting - ok - The microscope's light is designed to shine through the sample which isn't so good for us. I don't have any color balanced floods but I can correct for the fluorescent cast in photoshop (I'll include a corrected version of the one I sent you earlier with this email). Though not a great source, the lighting will be consistent (I need to work with the settings since the green channel is getting blown out due to the fluorescent wavelength).
Printer settings- Use highest resolution and print settings.
 

Some Background

I work in a Microbiology lab at the University of Virginia where I primarily do protein purification and electron microscopy. I have access to the Olympus which is a really nice scope. The attached CCD is only 764x486 pixels but you have to take into account that it has 3 ccd's each with that resolution plus it is attached to a great scope. You should be looking at 3 pl dots if Epson is telling the truth!

Dave, hope you don't mind but I plan to use our email exchanges in the
article as well! You are very knowledgable in this area I gather...how long have
you been an inkjet user? - kokleong

Sure, that's fine with me. I have a fair amount of experience with image analysis - technical not artistic. A previous project of mine was to use fourier transforms of cryo electron microscope pictures to reconstruct certain details of the structure that were not visible with just one image.

I haven't been an inkjet user since 1994 when I purchased the original Epson stylus color for $500. It didn't have a ink remaining meter so when it ran dry it clogged horribly. It didn't help that I tried to refill (didn't know about vacuum refilling at the time) with a 3'rd party ink that made things worse. Since then I've either used dye sub printers or the Fuji Pictography - an amazing printer. I decided I wanted my own printer for immediate feedback (nothing like instant gratification) and realized that ink jets had come a long way in the last 5 years. A couple months of following newsgroups, your website, and the epson list and I am the proud owner of a 900.

Though the 400x magnification (one of the earlier scans set to me by Dave) looks like it's got potential (for measuring etc), it does not have the clarity of the 200x. I suggest that the focus should be to get well defined dots...so that measurements can be made - kokleong

I did take one shot at 400x (nothing in between) Available magnifications that I can get to are:-20, 40, 100,400, or 1000x (have to use a drop of oil between the sample and the lens for this magnification).You probably won't like it as much at magnificatinos higer than 400 because of the paper texture. The problem is that the lens at 400x and above is so close to the sample that the desk lights don't do any good and I have to use the transmitive light of the microscope. I could play around with that some more - different angles etc. The other alternative would be to use the photo film since I don't believe it has any texture. One last thing - all the magnifications I am giving you are what the scope gives me.The magnificition we see totally depends on the resolution the file is displayed or printed at.  I'll try and get a shot of a reference image as soon as possible.

Measuring the dots is not too hard. There is a neat measuring tool in Photoshop 5. I found the diameter to average20 pixels for the 3 pl output. I look for nice round dots with no wicking since wicking reduces the size of the dot (the ink goes into the crevice instead of spreading out on the paper).

  I "scanned" the  electron micrograph grid (at right) at the same resolution (100x) that I have used for everything  else (except for the one 400x and the 200x that I sent you earlier). The grid has a pitch of 62 micrometers, a hole size of 42 um and a bar size of 20 um. Counting the number of repeating units divided into the number of pixels in that distance gives a value of 1.89 micrometers per pixel or .00000189 meters.Inverting that gives 529,363 pixels per meter (using the exact measurement) or 5,294 pixels per centimeter or 13,445 pixels per inch!

If one were to view the images on an average pc monitor (17inch monitor at 1024x768) (80dpi) the apparent magnification to people viewing the website would be 168 x (13445/80) [feel free to check my math!]

The above images are scanned at the same magnification (100x on the scope which translates to about 170x when viewed on a typical pc monitor) Difference in dot sizes are only comparable if done on the same type of paper.  Dots on film are a different size than dots on photo paper which will be different than dots on another manufactures paper.  Thats why I think there should be one standard paper to test everything on (Epson photo or film) and also should include the recommended premium paper when testing printers from other manufactures).

We can never prove which print is better with these high res scans since so many factors come into play:  The size of the dot, the density, the shape, the edge definition, it's interaction with the paper etc.  There is a lot to be learned from this though and I will come up with a list later after I do some analysis.

Variable dot size.

BTW, I'm not sure that the different size dots on the 360 scan are intentionally that way.  The really small ones are significantly smaller than the 3pl dots at 1440.  I suspect that they occur from splashing when the large ink drop hits or a small piece of the droplet breaks off as it leaves the nozzle.  Notice that the smaller dots are always next to a larger
one of the same color.

Till the next article...

As you can see from the above, the glossy film results in a much nicer dot (and a lot easier to measure).  You can also see that for the Photo Paper,  the texture of the paper is visible and one can even see how the ink wicks along the cracks in the coating. Hope your readers like the scans. I didn't enlarge them any since I didn't want to soften them. I'll go back and measure them in photoshop when I get a chance.