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Using Photoshop Cs4 for sketching

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#1 cpl43uk

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Posted 23 July 2009 - 06:11 PM

Hi everyone - have been a lurker for a while while I honed up my attempts at sketching through my Nexstar 8SE with this site as my inspiration (and indeed it was about time Astronomy Now added a "sketching" feature to its monthly magazine - a great section). I am new to the world of Photoshop CS4 however and have been using this tool to transform my sketches. In this regard I wonder if there are any astro-sketching digital tutorials that go beyond "invert" and "levels"? I usually "redraw" my star fields digitally using a brush tool for different star magnitudes (using duplicate copy of the original scanned drawing) and "rotate" the sketch circle to align for North/West axis etc but have never really cracked how to recast my galaxy or nebular "smudgies" with the sponge tool etc nor how to "digitally" capture my planet sketches. Even my "stars" could do with a bit of improvement (I use a standard brush palette but wonder if there are any better ways to digitally "sketch" a star with diffraction etc). Any tips would be a great help.

Chris

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#2 Jeremy Perez

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Posted 23 July 2009 - 06:58 PM

Hi Chris,

There is definitely a lot of inspiring work here--and based on the sample you posted, it looks like we'll be enjoying some very nice material from you too!

Re-creating an entire star field digitally hasn't always been easy for me to pull off. If enough differing magnitudes aren't used, it can look artificial. I created a fully-digital version of the Double Cluster in Perseus for comparison with a regular pencil sketch here:
Sketching the Double Cluster in Perseus - Pg 3
Putting a subtle bit of a halo effect on bright stars can really help pop them out (like described in this double star tutorial). Although if you put it on too many stars, it might start to look like overkill. For the fainter stars, experiment not just with smaller brush sizes, but with using a light gray instead of pure white. Also, see how differing the softness of your brush looks. A lot of times I'll use 60-80% softness on my brushes for stars. I think there's a lot of personal taste involved & eventually it comes across as looking like your particular style.

Creating diffraction spikes can be done with the smudge tool by clicking in the center of the star and the using the shift key to click another point further out. Or you can set up a custom paint brush that fades out after a certain distance and shift-click a fading line from the center. The tough part is making sure they meet at right angles. It might help to draw them perfectly vertical/horizontal and then rotate each one by a set amount afterward.

Painting nebula, galaxies & planets from scratch is a different critter altogether. Using a soft brush that is set to a low opacity and gradually building up lighter values with different size brushes is a good start. Following up with the smudge tool can help drag values you like into other areas where they are needed and can help beef up the form of the object instead of it being completely soft everywhere. Sometimes all the soft edges can look a little too CGI-ish and one option is to add some very subtle Noise from the Filter menu can help it look a little more natural. There are a LOT of ways to skin this cat--but it's really fun to experiment with. (I plan to introduce a variety of digital techniques in upcoming columns wherever I can.)

I hope you're enjoying the process. Thanks for sharing M17 & I look forward to seeing others when you're ready!

#3 cpl43uk

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Posted 24 July 2009 - 03:36 PM

Thanks so much for replying - love the work you do in AN. The halo link is great - I will try this out - but one more question if I can. Have yoyu ever managed to create a decent "stipple" effect in CS4? I'm thinking of Globulars and the need to create such an effect for the core. The "stipple brush" in CS4 does not offer circles but randomised square pixel blocks which of course can be blurred... unless I miss something.

Chris

#4 Jeremy Perez

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Posted 24 July 2009 - 04:30 PM

Hmmm...that's an interesting question.

I haven't tried that specifically in Photoshop. But what does come to mind, is that you could get a nice randomized effect by messing around with your paint brush settings. I'm using CS3, so I don't know if some of the menus are significantly different in CS4.

You could try to:
1) Select a small, round paint brush
2) Go to your brushes control palette (Window > Brushes)
3) Click the Shape Dynamics option and bump up the "Size Jitter" value try 50% & evaluate from there (this will randomize the size of your brush dots)
4) Click the Scattering options and bump up the "Scatter" value pretty high--maybe over 600% (this will cause the dots to fly around in various random directions relative to your brush stroke)
6) Click on the Brush Tip Shape option and raise the "Spacing" value to around 500% & vary from there (this will cause the dots to not bunch too close together & allow you to maneuver your brush stroke to spread the stars around better without huge clumps forming)
7) You might also try clicking the Other Dynamics option and raising the "Opacity Jitter" over 50% to vary the transparency of the dots.

Then just play around by varying your brush size and varying those settings to see what you get. It might provide some nice effects.

I made a quick test of that below. That is 4 separate brush strokes swirled around. 3 pixel brush size for the center, 2 pixel brush for most of it, and then dropping the overall brush opacity to 50% for the outer fringe.

I'm sure there are a variety of other ways of making that work too.

Let us know how it goes!

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#5 Jeremy Perez

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Posted 24 July 2009 - 04:35 PM

Oh! A quick word of caution. The 'random' effect might still generate some unintentional patterns in the image (like the sample I made above). That could lead to the impression that you saw star chains that aren't actually there. Keep an eye on those & delete out some of the stars if necessary to keep from giving the wrong impression. Probably the subtler you keep the effect the better. And then specifically place stronger (non-random) stars to represent the ones you directly plotted at the eyepiece.

#6 cpl43uk

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Posted 24 July 2009 - 05:11 PM

Thanks - I'll look at that.

Meanwhile I readdressed my M37 image with your suggestion of offwhites for the fainter stars- do not know why I'd never thought of that! Gives more depth in the result. I attach the before and after. Really interesting!

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#7 cpl43uk

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Posted 24 July 2009 - 05:12 PM

and after depth

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#8 cpl43uk

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Posted 24 July 2009 - 05:18 PM

before depth change

Chris

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#9 CarlosEH

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Posted 25 July 2009 - 04:14 AM

Chris,

Welcome to the Cloudy Nights Sketching Forum. The suggestions given by Jeremy above are excellent ones. As he points out it is a matter of experimenting with the brush size/softness and color in order to arrive at something that you (the observer/artist) is happy with. Your M17 and M37 observations are excellent. Thank you for sharing them with us all. We all look forward to your future observations on the forum.

Carlos

#10 Jeremy Perez

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Posted 25 July 2009 - 11:12 PM

Chris the before and after comparison on your M37 sketch is excellent. It's a little hard to tell in this post, since the 'after' image is quite a bit larger, but I brought it into Photoshop and scaled it down to the size of your original and looked at them side-by-side. It looks VERY nice. I'm looking forward to your next batch.

#11 WadeVC

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Posted 26 July 2009 - 03:57 AM

Sketching...with PhotoShop? No way! ;)

Here are a few tutorials that I posted here for members which may help you as well:

http://www.cloudynig...5/o/all/fpart/1


http://www.cloudynig...5/o/all/fpart/1

#12 Jeremy Perez

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Posted 26 July 2009 - 01:41 PM

Wade, those are outstanding tutorials. Chris, be sure to check those out.






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