arritt@kuhub.cc.ukans.edu (10/24/90)
We need to make some color slides of graphics produced on a 4D/25G.
At present our only facility for doing this is to take a photograph of
the screen, using a 35mm camera. If anyone else has done this, I would
appreciate your advice with regard to type of lens (we have both the
"normal" 50mm lens and a macro lens), type of film, exposure settings,
proper brightness settings on the tube, and so forth.
In case it matters, these are color plots produced using NCAR Graphics
version 3.0. The plots are generally similar to Example 7 of CONPACK.
Thanks for whatever help you can provide.
________________________________________________________________________
Raymond W. Arritt |
Assistant Professor |
Dept. of Physics and Astronomy | "everyone knew that as time went
Univ. of Kansas | by they'd get a little bit older
Lawrence, KS 66045 | and a little bit slower..."
arritt@kuhub.cc.ukans.edu |
arritt@ukanvax.bitnet |
slehar@thalamus.bu.edu (Steve Lehar) (10/25/90)
Photographing the IRIS screen and making slides is the most effective way of presenting your results at conferences and meetings, etc. I have done this several times, and the resolution of the slide captures everything on the screen with good fidelity, especially if you zoom your imagex up 2x. I usually use a regular 35mm camera on a tripod in a darkened room. Be very careful about reflections on the screen- it is amazing how you can look at the screen and see no reflections, but when you look at the pictures you see a prominent reflection from a power or "on-line" light of a printer or computer, or from a tiny crack in the window shade. Your brain filters these things out because they are at a different focus- until captured on the photograph. Be very careful to level the camera- in the viewfinder measure the angle between the bottom of the screen and the bottom of the viewfinder- get them exactly parallel. This is another thing that you might not notice otherwise, but looks very odd when you project your slides to the audience with a 2 degree list to starboard. Likewise, center the screen exactly in the frame. Move the pointer to the bottom-right of the screen where it disappears except for one last pixel. Again, if you are not thinking, you will not notice the pointer because you are so used to seeing it. When you see the photographs however it will appear prominantly distracting. Another thing that strikes you when you see the slides is the curvature of the lines due to the curved screen. You normally pay no attention to this because your eye compensates for it- like looking at a line of lattitude on a globe (looks straight) compared to seeing a projection of that globe onto a flat map (looks curved). Make sure that you are looking straight-on at the screen, so that the curve-up at the top of the screen is symmetrical with the curve-down at the bottom. This is done by aligning the camera exactly on the normal to the center of the screen. The curvature can be minimized by setting the camera far from the screen and using a zoom lens. Use a film speed that will "average over" many screen refresh cycles. If you set your exposure to 1/30 of a second for instance, you are unlikely to catch exactly one screen refresh, probably 0.9 or 1.2 or something, which will create funny looking results where there is a gap or an overlapping region. If you set for 1 second, then some parts of the screen will have been refreshed 30 times, and some parts 29, or 31 times. This ratio is sufficient to make the difference not noticable. I.e. use a long exposure time- this means of course that you must either use a remote cable trigger, or a delayed trigger, to avoid shaking the camera with your finger. When using a built-in light meter, zoom the lens to remove all the background blackness, set the lens till the light meter is satisfied, then un-zoom again for taking the pictures. In other words, don't let the border blackness (off the screen) influence the reading of the light meter. Straddle the settings that the light meter recommends- i.e. take three exposures for each frame, at three adjacent settings, to make sure that one of them is ok. The perfect setting may well depend on the type of image you have- are you interested in the detail in those dark corners, or do you want to examine the brighter regions. -- (O)((O))(((O)))((((O))))(((((O)))))(((((O)))))((((O))))(((O)))((O))(O) (O)((O))((( slehar@park.bu.edu )))((O))(O) (O)((O))((( Steve Lehar Boston University Boston MA )))((O))(O) (O)((O))((( (617) 424-7035 (H) (617) 353-6741 (W) )))((O))(O) (O)((O))(((O)))((((O))))(((((O)))))(((((O)))))((((O))))(((O)))((O))(O)
todd@mljsg.pharm.Virginia.EDU (Todd Tenenholz) (10/26/90)
Here at the Molecular Graphics Facility, we use the following: Cannon EOS model 650 camera, with 50mm lens and the Cannon compact-macro lens attachment. For Prints_________________________________________________________________ Kodak Ektar 25 film Vector drawings: f2.5 exposure 1.5 - 2 sec Raster drawings: f2.5 exposure 0.7 - 1 sec For Slides_______________________________________________________________ Kodak Extachrome 200 All Drawings: f2.5, 3.5, or 5.6 exposure 2" These pictures are genterated with the QUANTA molecular modeling package. Good luck! -- Todd Tenenholz, Molecular Graphics Facility, U. Md. at Batimore. Internet: todd@sg.ab.umd.edu
wade@fnord.asd.sgi.com (Wade Olsen) (10/26/90)
In <26308.27257d14@kuhub.cc.ukans.edu> arritt@kuhub.cc.ukans.edu writes: >We need to make some color slides of graphics produced on a 4D/25G. >At present our only facility for doing this is to take a photograph of >the screen, using a 35mm camera. If anyone else has done this, I would >appreciate your advice with regard to type of lens (we have both the >"normal" 50mm lens and a macro lens), type of film, exposure settings, >proper brightness settings on the tube, and so forth. I've had very good results with the following: Put the camera about 10 feet away from the monitor. Use and appropriate zoom lens. Use Ektochrome (spelling?) 100 film. Use 1 second exposure. Use 5.6 F-stop. Darken the room to avoid reflections off of the monitor. Use "normal" brightness settings. Use a delay timer. -- ++ Wade Olsen, wade@sgi.com, X1023
shenkin@cunixf.cc.columbia.edu (Peter S. Shenkin) (10/26/90)
In article <SLEHAR.90Oct25091039@thalamus.bu.edu> slehar@thalamus.bu.edu (Steve Lehar) writes: >I usually use a regular 35mm camera on a tripod in a darkened room.... > [[ followed by lots of good advice ]] Now, have you (or has anyone else out there) tried Polaroid color 35 mm film -- the stuff you develop in the funny little tank you buy from them, by inserting the film and the developer pack that comes with it? -P. ************************f*u*cn*rd*ths*u*cn*gt*a*gd*jb************************** Peter S. Shenkin, Department of Chemistry, Barnard College, New York, NY 10027 (212)854-1418 shenkin@cunixc.cc.columbia.edu(Internet) shenkin@cunixc(Bitnet) ***"In scenic New York... where the third world is only a subway ride away."***
rainer@boulder.Colorado.EDU (Rainer Malzbender) (10/27/90)
I just wanted to mention that there are people around who can take an Iris image file and convert it to a beautiful, saturated 4x5 negative using a good film recorder. Quality is obviously much better than a screen snapshot or color postscript printer. I think the cost is around $100 per shot. To avoid commercial messages on the net I will refrain from giving details. Email me if you're interested. (I have nothing to do with this other than knowing of such an outfit here in town). -- Rainer Malzbender "Ben, where are the hickory sticks?" Dept. of Physics -T.P. U. of Colorado, Boulder rainer@hibachi.colorado.edu 128.138.240.246
dave@imax.com (Dave Martindale) (10/31/90)
Some additional tips on exposure: 1. If you have a spotmeter available, this is the most accurate way I know to set exposure: Plot a square of full-intensity white on the screen, and read it with the spotmeter. Then give the film 2.5 stops more exposure than the spotmeter reads. 2. If you don't have a spotmeter, but do have a through-the-lens meter on your camera, fill the screen with white and take a reading, then give 2.5 stops more exposure. 3. Read the data sheet supplied with your film, and look for "reciprocity corrections". The manufacturer will often recommend additional exposure when making longer exposures in the 1 second range. However, shooting a screen does not really give 1 second of relatively dim light - it is 60 successive exposures of somewhat brighter light - so you may need less correction than the data sheet says. I suggest using full-intensity white instead of mid-grey, since few people will actually know how to display a true mid-grey on their CRT. Where does the magic "2.5 stops" come from? There are two ways of thinking of this: - the light meter reads the white area as if it were mid-grey (about 18% reflectance). The difference between 18% and 100% is about 2.5 stops, so opening the iris by 2.5 stops gives the correct exposure. - taking an exposure meter reading of a particular tone in an image, and then giving 2.5 stops more than the meter indicates, will place that tone up near the "shoulder" of the characteristic curve of a slide film - thus causing it to reproduce as fairly bright white, while still retaining detail in the whites.
donl@glass.esd.sgi.com (donl mathis) (11/03/90)
In article <1990Oct30.173541.14407@imax.com>, dave@imax.com (Dave Martindale) writes: > Some additional tips on exposure: > > 1. If you have a spotmeter available, this is the most accurate way I know > to set exposure: Plot a square of full-intensity white on the screen, > and read it with the spotmeter. Then give the film 2.5 stops more exposure > than the spotmeter reads. > > 2. If you don't have a spotmeter, but do have a through-the-lens meter on > your camera, fill the screen with white and take a reading, then give > 2.5 stops more exposure. > > [... other good advice ...] Also, if you are using a digital meter, you may discover chaos in the readings due to interaction between the sampling rate of the meter and the screen frame rate. I haven't measured our monitors, but i've measured normal TV displays, and both of my digital meters have trouble with them. You might have better luck leaning toward an analog meter. As to measuring white and opening up 2.5 stops, an alternative might be to measure what you consider to be "middle gray", and just use the reading directly. In fact, if you want to get picky about it, you're *really* looking for a black black and a white white, so you might want to create a gray scale on the screen, covering the whole range, and do some test shots of that to see how they reproduce. If you find you need to push the whites up a little higher, or the blacks down a little deeper, consider having your E6 film push processed. Conversely, but much less likely in my estimation, if you lose some of the lighter grays to white, or darker grays to black, consider asking for pull processing to reduce the contrast of the film a bit. On your test roll, bracket the exposures widely enough that you can get all the exposure information you need on one roll. Make your best guess and cover it by, say, plus or minus four or five stops. A roll full of gray scale exposures should tell you almost everything you need to know. -- - donl mathis at Silicon Graphics Computer Systems, Mountain View, CA donl@sgi.com I want my Ektar sheets!
brent@greylady.uoregon.edu (Brent Baker) (04/22/91)
I posting this for a friend, so please don't respond to this account.
Respond to: howie@jas1.uoregon.edu
------------------------------------------------------------------------------
Every now and then I've seen postings about how to take photographs of images
on the console; however, I never had any need to do such photography so I
never saved the postings. Now I have a need. We recently bought a molecular
modeling package and I would like to take publication-quality photographs of
the molecular models. The images are generated by the MIDAS software and
displayed on a Personal IRIS 4D/25. Can someone give me advice about the
best focal length lens, the type of film, exposure, etc.
Thanks
Howie
howie@jas1.uoregon.edu3ksnn64@cidmac.ecn.purdue.edu (Joe Cychosz) (04/24/91)
Film:
I use Kodak 100 print film for prints and Ektachrome 100 (Ektachrome
64 is no longer available) for slides.
I have not tried Ektar 125 yet. This is probably the best print film
to use as it has an incrediable grain density and excellent color. The
exposure settings will have to adjusted slightly. The next roll I shoot
will be Ektar 125.
Setup:
This is the longest and most crucial step. It is important to get the
lens as perpendicular as possible to the screen. Things to watch for are
monitors which tilt (like Suns or SGIs). I also try to get the lens as
close as possible to the screen and still be able to focus. This helps
reduce the effects of the curvature of the screen. For a 70-210mm Macro
Nikon this is about 2 ft at 70mm. This contradicts what one might think
in that one would expect the flattest photo to appear by getting as far
away as possible and shooting with as long of a lens as possible. The
problem is in the distoration in the lens system at 210mm. Keep in mind
that a macro lens works on a series of approximations. What results
is concave pillowing which is oppisite of the convex pillowing caused by
the curvature of the screen. The optimal flat picture occurs when the
convexed pillowing of the screen is balanced with the concaved pillowing of
the distortion in the lens system. Since I do not have a straight 200mm
lens, I have not been able to study and measure the distortion in the
macro.
One final note: I tend to shoot images that are either 640x480 or 512x
512 off of the SGI. I have shot full screen images, but the curvature of
the screen gets a bit difficult to control, especially with the 70-210
lens problems.
Exposure:
I use a 1/2 second exposure at f8 with half a stop added in. To bracket
the exposure I also shoot a f5.6 and a f11 exposure. With 100 speed film
the exposure can be fairly forgiving. That is to say, you'll get a
reasonable picture as long as the exposure and f-stop are within reason.
Never shoot faster than the refresh rate of the monitor, 1/60th. A wide
black bar will appear on the screen. This even goes for taking pictures
of monitors sitting in rooms. If you do you will endup with black bars on
the screen. For room shots I use 1/8 second or longer.
I have shot 1 second exposures at f8 and have had similar results.
Again, 100 speed film is pretty forgiving.
I have found the exposue metering systems in cameras to unreliable when
determining the exposue. This is especially true when shooting vector
displays. Also, you want to avoid full white areas such as menu areas
and the like. Change them to a 70 - 80% grey. The pictures will look
much nicer when printed.
Processing:
For prints I usually tell the people that process my film that the
roll contains computer graphics. Many film printers are computered
controlled and are setup for printing people, sky, grass, trees and other
things which you would find in normal photos. These printers usually
lose it when the get a picture with lots of black and fully saturated
colors. Vectors are the hardest to process.
I use a Noritsu and a Fuji machine for my processing. Usually
one or two units of density must be added (i.e., +1, +2) for computer
graphics shots. The process you are going through is to balance the
quality of the color with the quality of black. If you don't do this
you will end up with brown instead of black. The Noritsu and Fuji will
will print on the back of the photo what settings were used. So if you
do reprints bring the old photo in so the processor can see what settings
they used last time. Examples follow below:
Noritsu:
896 45 N N N 6 2
896 = Sequence number
45 = Film code (45 = Kodak 100)
N N N = Yellow, Magenta, Cyan print levels.
N = neutral, there will be numbers -1, +1, etc.
for non-neutral settings.
6 = Density setting.
2 = Ignore.
Fuji:
79 010005 28 +01
+0 -01+02 NN -5 0
79 = Sequence number.
010005= Film/vendor/speed code (Kodak 100)
010205 for Kodak 200 Gold
28 = Daily density setting, results from calibration.
+01 = Density setting.
+0 -01+02 = Cyan, Magenta, Yellow print leves.
+0 = neutral.
NN = Ignore.
-5 0 = Ignore.
One other problem the film processing machines have is alignment.
Lets say you are shooting pictures of some square 512x512 images.
The film processor will more than likely assume that the left edge
of the image is the left edge of the picture. I will not center it for
you. This will also happen with slides. To solve this problem two
things can be done. One: shoot a few fully exposed pictures at the
beginning of the roll so the machine can set where the left edge is
for the rest of the roll. Or two: us an alignment background pattern
like I do. This looks something like this:
----------------------------------
! ! !
! ! !
! ----------------- !
! ! ! !
! ! ! !
!-------! Image ! !
! ! ! !
! ! !--------!
! ! ! !
! ----------------- !
! ! !
----------------------------------
I am in the process of working on a calibration image which will help
the process people make there settings. I am also working on reducing
the yellow edges which appear (especially at red and green boundries).
I don't expect to have any of this done sometime soon though.