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DCP
member
Reged: 07/07/06
Posts: 98
Loc: Paducah, KY
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I have done some sketching, and definitely am no artist. What confuses me is when I invert an image to give me white on black, sometimes the results look really *Gosh, dang dibbity dag nabbit* . Some of the black on white looks bad but the inverted looks good. What gives, am I doing something wrong or does the subject matter? I have posted several pictures to the sketching gallery as examples. Most of the globulars and planetaries I like better as normal, white on black. Most of the galaxies please me more in black on white and look pretty pitiful in white on black. Check them out and see if you can help shed some light on my deficiencys.
thanks,
David
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16" custom dob/12.5 custom dob/ 10" dob travel scope
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cildarith
Carpal Tunnel
Reged: 08/26/04
Posts: 2173
Loc: San Diego, CA
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Hi David! Welcome to the sketching forum. 
I'm not quite sure how to answer your question, but I'll go out on a limb and try anyway. Faint objects (like most of the galaxies you're dissatisfied with) will be easier to see in the "negative" (black on white). Brighter objects will still look good when inverted to "positive" because there are still plenty of interesting details to see even if a little of the faint detail is lost.
If, after inverting your sketch the result does not seem to match what you saw at the eyepiece (either in intensity or angular extent) you might try lightly touching up the sketch in a program like Photoshop. I most cases, though, the details aren't lost, but the glare of the bright computer screen surrounding the sketch tends to spoil the faint parts of the image. If you can view you're inverted sketch on a black background in a darkened room, you should find all the faint details are still there.
Personally, though, I've looked through the images you've posted and I think they all look really nice rather they're inverted or not.
Also, even though posting sketches here as "positives" (white on black) seems to be the popular thing to do, there are many advantages to a negative sketch. I often download the sketches folks post here and re-invert them as it often gives a little more insight into how the original was created.
I look forward to seeing more of your (excellent) observations.
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Eric
6" f/6 Parks Newtonian
10x50 Bushnell Binocs
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DCP
member
Reged: 07/07/06
Posts: 98
Loc: Paducah, KY
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Thanks Eric,
I have been mulling this over since posting the message and may be on to something. When I get one I don't like, it is usually because the image looks flat (no detail) like the positive of the galaxy group. When I view a sketch in the negative I guess my brain knows it is a sketch and makes allowances. When I see a positive, my brain (critique) jumps to photo mode and I expect to see details like pictures posted (not gonna happen with me at the pencil!) Maybe I need to work on some of the finer details next time I do a galaxy group. After the Herschel list and Herschel II list, they all look like insignificant blobs, guess I need to see if I can tease any more details from them next time. Thanks again for the comments on the others, I especially like the way the globulars and planetaries came out, positive or negative.
David
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16" custom dob/12.5 custom dob/ 10" dob travel scope
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Erix
Toad Lily
Reged: 12/25/04
Posts: 20808
Loc: Ohio, USA
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Welcome to the sketching gallery, David!
I struggle with this too, and sometimes have had to either take a photo of the sketch so I don't lose contrast or actually go over it by hand after the initial scan to make more contrast on the sketch itself and then try again.
I don't like to go back over the sketch by hand because then the sketch as a black on white doesn't look like what I saw at the EP with regards to brightness. But then again, once I scan it, it looks fine as an inverted image. It still gives me fits!
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Erika
10" LX200 Classic, ETX70-AT, DS Maxscope 60mm, 12" Truss Dob, Orion ED80, WO Binoviewers, 10x50's and 7x50's Binoculars, Rebel XT 350
Having Fun in the Sun!
2007 July - tracking NOAA10963
We make a living by what we get, we make a life by what we give. ~ Sir Winston Churchill
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Jeremy Perez
Carpal Tunnel
Reged: 08/12/04
Posts: 1757
Loc: Flagstaff, Arizona, USA
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Hi David,
I agree with Eric, the sketches you've posted to your gallery are very nicely done. The planetaries really do look excellent. I was also impressed with how well you handled the subtle appearance of Palomar 11. That sort of gentle fade is really very hard to capture. Although your PN sketches sort of steal the show, the galaxy sketches are still excellent.
I think you are on to something with how the mind tries to put a white-on-black positive image into 'photo' mode and becomes more critical of the minute details. I recently did a couple sketches of NGC7009 that in my opinion turned out awful once I inverted them to positives. I think one potential problem is that it's even harder to get a soft, shaded transition to look good on smaller, threshold objects that have very gently brightness profiles...which makes the small, faint galaxies tough customers.
Galaxies aren't currently one of my strong suits, so take this with as many grains of salt as you would like =).
If I have time, one of the things I like to do when a sketch confounds me is to play with it in Photoshop (or other paint program). It allows me to lighten, darken, blur and sharpen different areas to see just what about my original graphite sketch was hurting its believability. Then the next time I'm sketching a similar object, I can try to compensate. Would you mind if I posted an experiment I did with your galaxy cluster sketch to this thread? Your sketch is already very nice in my opinion, but it might demonstrate a couple things. Let me know how that sounds to you.
Jeremy
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DCP
member
Reged: 07/07/06
Posts: 98
Loc: Paducah, KY
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Thanks for the comments, Eric and Jeremy, I was looking for constructive critisism for improving the process. Jeremy, I say go for it and see what you can pull out. If it ever does clear up here I will have to work on some more galaxy groups and try for more fine detail in them. Not much to see detail wise using heavy averted vision sometimes... Yes, the small planetaries are much easier to get "right", I won't dare scan my Helix however. It is gonna take a lot more practice before the big objects look acceptable to me.
thanks,
David
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16" custom dob/12.5 custom dob/ 10" dob travel scope
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stevek
Pooh-Bah
Reged: 04/16/06
Posts: 1246
Loc: west michigan
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Hey guys - I dont usually post in this forum - I havent 'earned the right' yet. but my season for clear skies and sketching will come. I still come through thoughn and look to admire and read and learn. David, your white on black gal cluster sketch looks OK! to me. I like your ?s and enjoyed the answers. I'm looking forward to what Jeremy will do with the same sketches... BUT for some reason the other attachments dont show up for me when I hit the link bar on your orig post. I'd really like to see them. Anyone know where I/my computer lost them? It says 14 attachments but when I hit the link, it only shows the same one. 
Steve
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DSO 8" f6 DOB w/ 8x50 RACI & 2"Crayford
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Jeremy Perez
Carpal Tunnel
Reged: 08/12/04
Posts: 1757
Loc: Flagstaff, Arizona, USA
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Hi David,
This galaxy sketch is really very good, so any difference I show will really be pretty minor. One of the things I usually do after scanning is to adjust the luminosity of the sketch so that the stars brighten up and the black background also gets brightened just enough to allow the faint nebulous regions to show up on various monitors. To do that, I usually use "Curves", but "Levels" will work for most adjustments too.
Below is what the Levels dialog looked like for your image. I moved the white slider (C) over to the left quite a bit, and this helped to brighten the stars. The black slider (A) for the darkest areas was fine as-is. I adjusted the mid-tone slider (B) a little bit to help darken the galaxies back up since brightening the stars had brightened the galaxies too much in the process.
Finally, I adjusted the black output level slider (D) to the right a bit to lighten the deepest shadows. If you look at the Info palette to the right, it shows the before & after values of the background. The "4-4-4" before value is almost totally black. Bringing it up to "11-11-11" lightens it up just a bit. I usually shoot for values from 10 to 15. I haven't turned it into a science, but if the background is too dark, then people with lots of light glaring off their monitors, or with less than ideal settings may miss a lot of the fainter details in the sketch. If the background is too bright, then the whole thing can look washed out.
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Jeremy Perez
Carpal Tunnel
Reged: 08/12/04
Posts: 1757
Loc: Flagstaff, Arizona, USA
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This shows the difference before and after the levels adjustment. Depending on how the observation looked to you, I may have left the galaxies brighter than they should be. To fix that, you would play with the midtone slider (marked 'B' above) to darken them.
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Jeremy Perez
Carpal Tunnel
Reged: 08/12/04
Posts: 1757
Loc: Flagstaff, Arizona, USA
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The next thing I did was to see what some blurring would do for the galaxies. There appear to be some pencil swirls atop a few of the galaxy cores. They are really subtle and aren't very distracting, but blurring that out seemed to help a bit, as well as smoothing the transition along the outer fringes of the galaxies. I also use dodge and burn tools to keep the brightness profiles of the galaxies smooth in areas that blurring didn't get. After that, I added a bit of noise to the sketch to make the artificial smoothness of the blurring look more like a regular pencil sketch on slightly rough paper.
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Jeremy Perez
Carpal Tunnel
Reged: 08/12/04
Posts: 1757
Loc: Flagstaff, Arizona, USA
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One other thing I did, was to differentiate the magnitudes of the stars a bit more. This part is a total guess, and would depend on whether there actually were noticeable magnitude differences in the star field. Trying to convey this aspect is something I've really been enjoying when sketching, but it's obviously up to each individual observer how much to fret over it.
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Jeremy Perez
Carpal Tunnel
Reged: 08/12/04
Posts: 1757
Loc: Flagstaff, Arizona, USA
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Finally, I inverted the sketch back to black on white to see how it would look as-sketched. That helps me to know how the blending and density of the shading would look while sketching. The difference is really pretty subtle, and I'm not sure whether it's necessarily an improvement. The main idea is to just play with the sketch in positive format until it's more to your liking, then inverting to negative format to see what the pencil version of that would look like.
Sorry it took so long to get back here and post this. I'm looking forward to your future sketches!
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DCP
member
Reged: 07/07/06
Posts: 98
Loc: Paducah, KY
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My hats off to you Jeremy. That is exactly what was wrong with the pictures. I guess I need to use scrap paper to put lead on and smudge stick it over to the drawing. The swirls were lead from the pencil put on the paper and then smudge sticked around to try to get the look right. As a negative, they are not all that noticable, but in a positive, they really detract from the drawing. Only thing I can see to critique on your rework of the galaxy drawing is I only wish they were that easy to see at the eyepiece. They were much fainter and a couple took heavy averted to pull out. Guess that is hard to represent in a drawing? I need to print out this thread and your reworks to study before trying another one. THANKS GUYS, that is exactly the kind of help I was hoping to find here. Us non-artists have a hard time putting this stuff to paper, my 19 year old however could do it in his sleep, he has the gift, I however have to work hard at it. Gotta work on them some and post a few to see if I have improved any, the mere thought of posting them here will push me harder! 
thanks again,
David Paessler
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16" custom dob/12.5 custom dob/ 10" dob travel scope
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Erix
Toad Lily
Reged: 12/25/04
Posts: 20808
Loc: Ohio, USA
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Quote:
BUT for some reason the other attachments dont show up for me when I hit the link bar on your orig post. I'd really like to see them. Anyone know where I/my computer lost them? It says 14 attachments but when I hit the link, it only shows the same one.
Steve
Hi Steve! You most certainly don't need to earn the right to be in this forum. We're glad you popped in.  Regarding your question, if you mean the area that I've circled in blue in the image below, that means how many times that attachment has been downloaded. If a person isn't logged on CN, they have to click on that link for the image to download. So there aren't actually 18 images in this example. But it has been downloaded 18 times.
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Erika
10" LX200 Classic, ETX70-AT, DS Maxscope 60mm, 12" Truss Dob, Orion ED80, WO Binoviewers, 10x50's and 7x50's Binoculars, Rebel XT 350
Having Fun in the Sun!
2007 July - tracking NOAA10963
We make a living by what we get, we make a life by what we give. ~ Sir Winston Churchill
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Jeremy Perez
Carpal Tunnel
Reged: 08/12/04
Posts: 1757
Loc: Flagstaff, Arizona, USA
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David, the stubborn ghosting of pencil swirls bugged me on my sketches for a while before I switched to shading with a blending stump dipped in a graphite palette off to the side of the sketch. Here are a couple links to observations I made where I originally sketched the shading of the object onto the paper using a pencil and then blending it afterward (see bottom half of each observation).
M8
M17
The pencil scratch marks were hard to eliminate and I personally didn't care for them. So those observations also show recent new sketches I made with the blending stump/graphite palette method (top half of each observation).
Here's another version of your sketch that's darkened up a bit to convey the subtler view you described. It's hard to come up with a happy medium between making the objects reliably visible, and making them appear as subtle as they really were.
Also, I hope you keep on posting those sketches, even if they have tenacious pencil marks. They are very nicely crafted nonetheless.
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Edited by Jeremy Perez (01/10/07 11:51 PM)
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CarlosEH
Post Laureate
Reged: 01/19/05
Posts: 3259
Loc: Pembroke Pines, Broward County...
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Jeremy,
Thank you for taking the time out to help a fellow observer on the forum with a problem. Very helpful pointers given.
Carlos
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Jeremy Perez
Carpal Tunnel
Reged: 08/12/04
Posts: 1757
Loc: Flagstaff, Arizona, USA
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Thanks Carlos. I should also mention that varying your pencil and paper choices can make a big difference in how blendable your pencil marks are. Although I prefer the blending stump/graphite palette technique, it's not the only way to overcome that issue.
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Orion SVP 6LT (6" f/8 Newt) || Orion XT8 (8" f/6 Newt) || 15x70 Oberwerk Binoculars
The Belt Of Venus || Astro-Sketch Gallery || Astro-Sketching Resources || Astro-Photo Gallery
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DCP
member
Reged: 07/07/06
Posts: 98
Loc: Paducah, KY
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Jeremy, maybe it is my drawing equipment that is making things harder than they need to be. What are you using or what do you mean exactly with "blending stump, graphite pallete"? I am familiar with the blending stump, my graphite pallate is some pencil scrubbings on some scrap paper. For large area shading, a fingertip is useful to me. Is there better stuff out there I should be using?
thanks again,
David Paessler
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16" custom dob/12.5 custom dob/ 10" dob travel scope
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DCP
member
Reged: 07/07/06
Posts: 98
Loc: Paducah, KY
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Steve, sorry for the late reply. Thanks to Erix for answering your question. I too like looking through other people's sketches here. You can go to the sketches picture gallery (at the bottom of the forums list) to see all of the sketches loaded there. If you are looking for the other sketches of mine, you can search them for the user dcp and see the planetaries and globulars I have done also. It is definitely a learning experience for me. As in anything, there is a lot of room to grow our skills. A special thanks to Jeremy for helping me through some issues I was having with my sketches! Hope you can pick up some tips too Steve, and post some of your work.
David
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16" custom dob/12.5 custom dob/ 10" dob travel scope
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Jeremy Perez
Carpal Tunnel
Reged: 08/12/04
Posts: 1757
Loc: Flagstaff, Arizona, USA
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Hi David, sorry about talking in shorthand up there. Yes, I was referring to a spot of paper where I've scrubbed in a dark patch of graphite. I then dip my blending stump into it and apply that directly to the sketch. Also, I think the quality of your large globular sketches testify to the usefulness of fingertip blending. As to any other tools you could use, you may want to grab a Kneaded Eraser from an art/drafting supply store. It can be balled up like clay into just the right shape to gently lift graphite from a sketch and get some very controlled blending effects.
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