NetNotes
older 1k × 1k cameras with 14 bit depth, the images are going to look disappointing no matter what soſtware, computer, or printer you use. John Mardinly
john.mardinly@
wdc.com Mon May 17 I recall an interesting discussion recently with a curator of
photography at a well known museum here. She pointed out that the physical nature of a photograph is quite different from a print. In a print, the ink is deposited in a single layer on the surface of the paper. In photography, both in the film and the paper, the silver is embedded in a deeper matrix in the paper. Te end result may very well be that “breath-catching” moment when looking at a photographic micrograph, since the image is formed by a combination of simple reflection and interference within the matrix. So, beauty is a little more than skin deep. Joel B. Sheffield
joelsheffield@gmail.com Mon May 17 Adjusting the brightness and contrast is not enough. I have been
doing fine art photography and showing my work in galleries and Photoshop is the program to use regardless if you are doing color or B&W. I don’t print much of my scientific stuff anymore since papers are submitted electronically but aſter Friday’s discussion I sent one of my DM3s (converted to 16 bit grayscale tiff) to my home machine where I have my Epson 7800, a 24 inch carriage archival pigment inkjet. Te print I made from our 2K Gatan camera looked as good, if not better, than any of my silver gelatin prints of the past. I purchased my first high-end printer (Epson 2200) about five years ago. I was disappointed with the results because they weren’t as good as prints from an older printer I had. I then took a course on digital printing and I took another more extensive course a few years ago. Photoshop does a good job of color management that a number of other soſtware programs don’t do (PowerPoint for example). My Epson 7800 has eight different inks (3 blacks if I remember correctly). A new Canon I saw advertised in one of my photo rags had 12 inks. Standard CMYK (4 inks) just doesn’t do it because the blacks usually come out with a color cast. To get a good print you need to match the printer, the inks and the paper. Tis is done with a color profile file that is usually available on the paper manufacturer’s web site. You also need to have a color calibrated monitor and work in a room with subdued light. One of the newer Epson printers is the Epson 3880 and it runs around $1500. I keep mentioning Epson because they had the market until a few years ago and I haven’t kept up with the other brands. Tese are inkjets and they need to be babied otherwise you will have problems but they produce fantastic results. I have a book on printing that I have read cover to cover. It is Color Confidence: Te Digital Photographer’s Guide to Color Management by Tim Grey. Now that says color but the concepts are similar. I have absolutely no desire to go back into a chemical printing darkroom. Norm Olson nholson@
ucsd.edu Mon May 17 First: Digital Micrograph is a great program but not for printing.
For printing you want Photoshop. But you can use almost any version since Photoshop 5. Te trick is simply to understand how to print and what to print on. Best B&W will be Epson for so many reasons and three major patents that it isn’t worth talking about. All pro photog- raphers use Epson printers. We have tested printers for years now and the Epsons are clearly superior. Te best current model is the Epson 2880. It will print up to 13″ × 17″ which covers everything except posters (We use an Epson 9600) Te K3 (3 blacks are important because you can print at higher densities than 300 ppi. Tis is because the dot pattern can be denser if you have gray inks. Gray inks are very important for the best but you can do very well with a C88 plus on good paper. Te C88 plus printer costs $85. Te 2880 is about $800. Te C88 plus prints the best images on plain paper. We have always compared our prints (and still do) to the same negative printed on Agfa Brovira paper. If you have enough pixels then the prints will be very close. Te photograph will be sharper but only to a trained observer.
2010 September •
www.microscopy-today.com
Now I have heard all the arguments about resolution and pixel size but for a biologist there is an important and rather simple calculation that I think defines the problem. Te old photo prints were 8″ by 10″. A good digital print is about 600 ppi. Te simple math says 4800 × 6000 pixels. Tat is going to take a rather large montage to equal with a smaller digital camera. So you either need a larger format camera, a large number of montage images or record on film and scan. 4k cameras are out of my laboratory’s budget but a $700 scanner can do 2000 ppi (we have calibrated it) Epson wouldn’t you know. (D750-M pro or V700; also tested 4880 and 4990) It is quite easy to get enough pixels by scanning at 1200 ppi and then we are totally digital. When you want the best you can go up to 6000 × 8000 pixels. in one pass! So the procedure we follow is as Tina said: Levels Adjust histogram till black arrow and white arrow just touch. Ten print. adjust gamma by at least 1.2 print again repeat until it is clear you have too much gamma. Why? Because gamma is like focus you don’t know that you have too much until you go past it. Aſter you have chosen the best gamma value you do a final histogram stretch to reclaim the contrast. We do this selectively in the dark region of the histogram where there is little data that will be masked out (lost). We can reclaim a huge amount of contrast while binning less than a couple of percent of the data Te best histogram to start with is one that has no values in the dark or white regions (about 15–20 values) this insures the image is neither over or under saturated. When scanning, we scan in 16 bit mode then do a histogram stretch in 16 bit mode in Photoshop before converting to 8 bit mode for gamma adjustment and printing. Note no print driver known can handle native 16 bit images. Ten proceed with Levels adjustment as outlined. With a good image, we can get publishable quality prints on any Epson on any paper. Secondly, you are not doing anything that is not scientifically correct. John M. Mackenzie
john_mackenzie@ncsu.edu Mon May 17 When moving the white and black sliders in the Levels box within
Photoshop, it is sometimes difficult to see where the histogram ends because so few pixels make up the darkest and brightest parts of the image (on the other hand, the Photoshop-mimicking free program, GIMP, provides a log scale histogram so that every pixel tone can be seen). Here’s a tip: if you want to see the parts of the image with the darkest and brightest pixels, hold down the alt key (PC) or the option key (Mac) while moving the sliders. For the black slider, the image will turn white the moment you move the slider; for the white slider, the image will turn black. Move the slider until significant parts of the image appear, then back off until these disappear. Note the word “significant:” some parts of the image may be detritus or artifact. When these parts of the image appear, it tells you that a move of the slider any closer to the center of the histogram will result in setting the darkest and whitest parts of the image outside the dynamic range of the image (clipped or saturated values), which is okay for known, non-significant parts of the image, but not okay for significant parts as it will block detail. No one has addressed the issue of sharpening. I’ve noticed that some journals discourage sharpening, but since this thread speaks to printing to hard copy, sharpening may be an option for bringing out local contrast to better reveal details. Some call this “enhancement” or “doctoring” while others call it “resolution.” My thought is that any improvement in revealing detail is something that should be pursued: over-sharpening, or sharpening to the point at which artifact is confused with biology/materials must be avoided. A way to provide local contrast consists in duplicating the background layer in Photoshop to make a layer above the first layer (Layer > Duplicate Layer). Ten use the High Pass filter (Filter > High Pass) and set the level between 1 and 4 to the point at which edges are visible but not so much the features. Set the Layer mode (in the Layers palette) to Hard Light and the image is sharpened. By clicking
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