More Exposure testing and Dot Testing

[jsheridan]

Fired up Freehand 10 last night and made myself some new test films. It's the only program that allows you to assign different screen angles and line counts on the same document page. I made this back when I had 300 screens with 15 mesh counts. Took us a few weeks but we were able to narrow down the dot ranges that our screens could handle. This helped the artists when they made films as they knew where to pull and push levels to reach the desired dot. Our prints got better over night and it removed a variable.


The goal of my plan is to find the best dot that is as wide as three threads of the mesh counts that I use. The only way after math to determine if you have the right dot, is to look at it through a microscope on the film, the screen, some paper and then a shirt.

I did that today. Started with a DOT frequencies test to find what tonal ranges and line counts work best with my equipment. Started with my 255/40 mesh @35n today and here are some of the results. The biggest finding is that my printer is a POS and drips horribly.  under 100x zoom my films are nasty.. they burn good but I'm getting an exact duplicate on screen with a corrupted edge that is effecting my 1/2 tones. After seeing this I'm not going to attempt to pull films here for any sim process or any series kind of tonal blending until I can control my dots a little better.

Have plenty of testing still to do but here's some pics of my test. Just put the smartphone up to the viewer on the scope in B&W mode and got some great pics.

Test film and 60x - 100x scope.
 

41 line 5% dot on Film
 

41 line 50% dot on fillm


41 line 50% dot on Screen


41 line 50% dot on Paper


41 line 50% dot on Shirt

[Fluid]

Very nice.

I did the same here just a little bit ago with one of my printers.  I did both round and elliptical dots ranging from 15 - 75 LPI

Best way like you said and helps both the production dept as well as the artists. Knowing your limitations helps for better prints and maximizes production. 

[blue moon]

very cool! Make sure you keep us posted on your progress. While you might not see a lot of responses, this is the stuff that all of us here can use and see more than once!

thanx!

pierre

[jsheridan]

I dove in the deep end with this when I should have waded into the shallow end first.

Trying to see what dots I can hold is almost pointless w/out first calibrating my dot curve inside AccuRip, I've got to get my hands on a Densitometer so I can read my output films. Once I calibrate then I can make the proper films and re-test.

Holding my camera to the scope has been cumbersome as well and it takes multiple shots to get a good one SO.. I ordered a USB microscope. The results are easier to see, photograph and document. It has 20x to 400x zoom with a stand so I'll be able to see the stencil wall vs the direct overhead look I have with my current scope. Then when not looking at screens, I can use it with my son to look at bugs..

Here are some results from the 205 mesh. Not sure of the micron yet but the 45 line 50% dot is my target 3 thread dot.

The edge detail for a 45 line 50% dot


45 Line 50% Elipse dot @ 25 degree. Notice the 3x3 grids.



Plenty more to come as more testing tools come in.

[bimmridder]

I wondered if anyone here has used a densitometer. When we first got out direct to screen,we adjusted our curves in the rip. We knew that the dot we said was 27% would actually print as 27% on press. It took a long time to dial this in just right, but talk about controlling a variable. It was a matter of starting at ground zero with the settings as they were. Making a screen and measuring the dots. Making adjustments to the curves, make a new screen,print and measure, over and over until what we said was 27% printed as 27%. I had an expert doing all  the work. I just made the screens and printed.

[blue moon]

I wondered if anyone here has used a densitometer. When we first got out direct to screen,we adjusted our curves in the rip. We knew that the dot we said was 27% would actually print as 27% on press. It took a long time to dial this in just right, but talk about controlling a variable. It was a matter of starting at ground zero with the settings as they were. Making a screen and measuring the dots. Making adjustments to the curves, make a new screen,print and measure, over and over until what we said was 27% printed as 27%. I had an expert doing all  the work. I just made the screens and printed.

I've dialed in my films to print exactly (+/- 2%). Even tried measuring the shirts, but the readings were too erratic and in the end I concluded that it might be more trouble than it's worth. Now that you have me thinking about it, maybe I should test it for the particular type of shirt and make the customers with critical color pay for those.  hmmm . . .

pierre

[bimmridder]

The tough part is finding the time,someone with the knowledge, and the actual meter. It is very cool to see the results.

[jsheridan]

make a new screen,print and measure, over and over until what we said was 27% printed as 27%.

This is exactly what and why I'm doing this, to control my dot.

This will be my third time linearizing the film output devices so thankfully I know how to do it. It just takes some time and a few screens to dial it all in.

[brandon]

Thank you for posting this John! This is awesome and very, very informative!

[mk162]

Now, not to throw a wrench into things, but linearization and dot gain compensation are 2 different things.

Linearization is adjusting your films to print the correct dot size and to allow for ink spread for your films.  Maybe your printer compensates for this, but mine doesn't I needed a transmission densitometer to measure it.  Mine was between 10-15% high.  i am next going to start working on true RIP dot gain compensation, rather than separate settings between corel and photoshop.

I can't wait to see how it works out.  The RIP adjusts for all of this, I just haven't been using it to it's fullest.

[ScreenFoo]

Great thread here people.  I'm with bimmridder--just wish I knew someone around here with a densitometer.  Anyone have brand recommendations?  I used an ancient X-rite back in the sign days, but that was worse than programming a VCR...

John--Nice pics.  What kind of scope are you using?  I keep looking for a higher power USB scope that isn't biological style...

I've been measuring dots with a less optically accurate Celestron USB rig than John has--and although it's tedious to make 'linear' adjustments, it's produced marked results. 

[mk162]

i have a couple, where are you located?

[inkbrigade]

Wow! This is the kinda thread i'm always looking for. Thanks for posting John.. Although your expertise makes me hate everyone that comes in to interview for a job and can't even explain to me what squeegee durometer is. ugh.

[jsheridan]

My buddy's shop has an imagesetter... the quality of the films.. droooolllll... 

I'll take some cell phone pics today and compare it to our inkjets.. prepare to enter the 'I wish i had that' world

[Dottonedan]

These shots are very telling. Very educational. Very beefy.   emmmm. good food.

Thanks!!!!