NetNotes
And I really want to do this right the first time. Which leads to the questions * What programs are people using that provide for better micrograph processing, * What printers are good. Frankly, the best we have here is not much improved over my very old HP 1200 toner printer in the lab. Again, as with processing the images, the best I can get is on my home system, where I use an HP6400 multifunction system. And I don’t like those prints. So, thanks in advance. Paul R. Hazelton
paul_hazelton@umanitoba.ca Fri May 14 I’d like to respond to the recent posting by Paul Hazelton.
However, I would like to first put out a disclaimer: As a person who has been involved with digital imaging on TEMs and SEMs for a while, and who is currently selling these systems, I am definitely biased towards digital imaging systems. Now, Paul brings up a number of good points. Perhaps I can add some light on this from another direction. Tere are many issues that have an effect on the “quality” of images, and I think it’s instructive to look at some of them. Let’s start by looking at resolution, as it is oſten stated that “film has a higher resolution.” It turns out, in fact, that it is true. If you look at the MTF of film compared to that of, for example. P47 (scintillator material), which has been measured (references available, please ask), we find that film has around twice the resolution (50% point of the MTF) than the scintillator has. But the ultimate limit of the entire system is of course determined by the resolution of the TEM. John Spence measured the MTF of SO-163 and came up with about 32 lp/mm, or 30 micron, which also depends on the development procedure. Tat means that if you have a TEM with 0.2 nm resolution, you need a magnification of at least 150 k× to see the detail on film. For digital, you need to go to something like 300k×, but then you see the same detail. You lose some field of view, but you can resolve whatever the microscope can. So, resolution is clearly not the issue. Well, then it must be the dynamic range. But that’s not it either. Our eyes have a dynamic range of maybe around 7 bits (we can distinguish perhaps 100 levels of grey). Film can have a different dynamic range, depending on the development process, but typically that would be 6–12 bit (64–4000 levels of grey, the latter only with significant reduction in resolution). Digital cameras can have resolutions between 12 and 16 bit, depending on various factors such as cooling, etc. Now, everybody would agree that 64,000 levels of grey are better than 200. So why do some people see digital images as inferior? I think the answer lies somewhere else. First of all, most people don’t use the full dynamic range of their cameras, and it may not always be possible. Te information may be “bunched” in a small range of grey levels, and then this information is “stretched” and “shiſted” to make it visible to the eye. In extreme cases, one could wind up with only 50 levels of the 64,000 used, which would then be visible in areas that have fine grey level details. So, look at the histogram when you acquire images. If the data is all bunched up at one end of the histogram, the images will probably not look good. For example, if the background is all saturated, it is probably a good idea to reduce the beam current or exposure time. Ten we have the linearity of the digital cameras. As opposed to film, they are very linear, which is a good thing, with a sharp cut-off at the low and high intensities. Film, in contrast, has an S-shaped response curve (gamma). Tis makes for pictures that are easier on the eyes, as the sharp cut-offs at saturation are absent, but makes film much less useful as an analytical tool. Of course, you can mimic that with a digital camera, as we can usually set the display to various gamma values. Te last thing I think contributes is the fact that digital images are usually observed on a monitor and are very easy to manipulate. We CAN go to the extremes and beyond by simply clicking a button. We CAN magnify the image on the screen to ridiculous proportions just by selecting it with the mouse. Tat’s not possible with film. You have to go back to the dark room and play with chemicals for an hour. Because of that we have all
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learned that we can’t blow up a negative too much, and so we never see the effects. Film definitely has an advantage in terms of information density. It can record more information over a larger area. But digital has the advantage in almost anything else, and the film’s advantage can be overcome with things like taking serial images and montaging them. It takes a bit longer, but serves the same purpose. Now for Paul’s questions. I think that Photoshop and Illustrator are fine products, but they are designed for color photos with the aim of publishing them. Photoshop alone, for example, does not even have the concept of magnification, unless you use some plug-ins. I am not so familiar with Illustrator, but I guess it’s the same story (this may be a good point to remind everybody that I am earning money from selling a competing product and you should come to your own conclusions). So, the first thing I would suggest is to look at soſtware that is made for microscopy, and go from there. And you don’t have to stick with what we are selling; there are many fine products out there. As far as the printer goes, it is a developing story. My suggestion would be to look for a high quality ink jet printer and use high quality paper (photo quality) for the best results. Get a good, but inexpensive laser printer for the routine pictures. I have had good results with an Epson R800 Ink-jet printer (I think they don’t make them anymore). Mike Bode
mike.bode@
resaltatech.com Fri May 1 I’m with you guys; I miss the beauty of darkroom photography.
I could carry on at length, especially about digital image manipu- lation. Te *short* answer to your immediate question is, using Photoshop, go to Image - Adjustments - Levels (the first thing in the picklist for a reason). See histogram. Adjust the white triangle and the black triangle toward the edges of the histogram, and then move the gray triangle in the middle to where you like the results, usually more toward the peak. If you still want more contrast *aſter* this, *then* use Contrast and Brightness. Tis is the best thing you can immediately do, plus it’s just about all you can do according to the MSA guidelines on the ethics of digital imaging, which I can’t find on the new, redesigned MSA site. Tina (Weatherby) Carvalho tina@
pbrc.hawaii.edu Fri May 14 I might add a bit more to what Tina suggests. And I also
understand and appreciate the fine points of wet photography. I have a very good 4K CCD camera on one of our TEMs and I rarely use it. On the other hand I have not printed in the darkroom for about 5 years and our last Durst enlarger is on its way to salvage (let me know if you want it). I capture images on film and then we scan the film at appropriate dpi for its intended use (usually 600 dpi for must images). I find I can capture better grayscale images on film faster than if I use the digital camera and it is much easier to manipulate the contrast gamma, and brightness when scanning to end up with a very reasonable digital image. However, I also can easily stigmate and focus on the viewing screen and that is also almost a lost art. Te 15 min it takes to develop 30–40 negatives is a minor inconvenience for the larger and higher quality viewing area. Yes, we then have to put in time scanning but the final outcome is worth the little extra time. I suggest you use Photoshop and use “Layer >>> adjustment layer >>> levels” rather than “image >>> adjustment >>> levels.” Using the new adjustment layer lets you modify the original image and then save the image. Tis does not alter the original scanned image but rather saves the changes in a new layer. Ten when you next open the image you can easily readjust, again without changing the original image. When you finally get the image you want for a specific purpose you can just flatten the image and do a “save as” to save the modified image. You still have the original unmodified image to archive. Debby Sherman
dsherman@purdue.edu Fri May 14 You did not state what sort of “used Gatan system” you have, and that may be your fundamental problem. If you have one of the
www.microscopy-today.com • 2010 September
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