Granite Speed Power Test

[Steve Clarkson]

I have attached three photos showing the results of my first speed power test on granite.

In the first picture, the top row shows a picture processed through Photograv using the Cherry setting. It was processed and engraved at 300 dpi and 100 speed. The first picture is at 30p, then 40p, 50p, 25p, and finally at 33p to appease Frank. Clearly, the best setting was 100s and 30p.

The second row of the first picture shows increasing the dpi to 600 at 30p, 40p and 50p. Then decreasing it to 150 dpi at 100s and 25p and 30p. The last picture of the row was done at 25s, 20p and 300 dpi just to see if slowing it down would help. It didn't and none of the pictures in this row were better than the 100s 30p and 300 dpi.

The second picture shows a repeat of row 2 of the first picture (sorry, I should have cropped that out). The second row of the second picture shows the photo processed through Photograv using the Granite, Gray Spectrolite (hey, do you spell grey....g-r-e-y or g-r-a-y?). In the first five pictures it was processed at 300 dpi and 100s. Starting in the first photo the power was 30, then 40, then 50, then 25 then 20. The last picture in the row was at 600 dpi 100s 20p. I was kind of undecided if the best one was at 300 dpi, 100s and 20, 25 or 30 power.

The third picture shows kind of the final results. The first picture was at 1200 dpi 100s 30p and it was completely washed out. The next two were SUPPOSED to be just repeats (100s 30p 300 dpi cherry and 100s 30p 300dpi grey) but I accidently got amour all on them AFTER I engraved them. It turned out to be an interesting effect.....it kind of toned down the whiteness. Pictures 4 and 5 had the same exact settings as 2 and 3, but I put amour all on the tile BEFORE I engraved them. The result is that the engraving was no better than it was without putting the amour all on first. The last picture had the same settings as pictures 2 and 4 but I tried to smear on oil based titanium white paint. It made the picture whiter, but it was alot more work trying to rub it in evenly, and I'm not sure it looks that much better than without the paint (or even better than the one with the amour all put on after the engraving).

The last picture is the original.

Now clearly I could have done a better job processing the photo in PhotoPaint (changing the tone, etc.) and I think that's why her nose is kind of faded out. But regardless of the pre-engraving photo processing, I think the results are clear enough.

The best settings from this test were 100s 30p and 300 dpi and it was a toss up whether the photograv cherry or Gray Spectrolite were better.

My next test will be to compare the 2" lens to the 1.5" lens.

What's your opinion? Feel free to post a picture of your own tests.

[Margaret Turco]

Very thorough test Steve, thanks for posting. Is there a noticeable difference in the engraving depth with different settings, as you mentioned in another post? In any case, the quality of the image is very apparent.

p.s. I spell it GRAY

[Tim Bateson]

Steve, Try your test again with a different image and you me well get different results.

[Dee Gallo]

Steve- I'm curious to know if you did anything at all to the photo before processing or did you just put it into Photograv "as is".

If you changed it to greyscale first, could you post that picture so we can see the contrast before it got processed? This is the crux of the matter as far as I can tell. I could be wrong...

thanks for posting those interesting tests, dee

[Frank Corker]

Steve,

Run this one through. Choose Stucki. Set your speed to about 43.
I'd be interested to see what it looks like alongside your other ones.
I haven't processed it through photograv, I haven't altered the dpi
setting, all I've adjusted is contrast and brightness. I ran a test here
and it came out extremely well.

[Steve Clarkson]

Is there a noticeable difference in the engraving depth with different settings, as you mentioned in another post?

Absolutely no difference in depth whatsoever. That tells me that more power is NOT the solution to getting a deeper image.

[Steve Clarkson]

Steve, Try your test again with a different image and you me well get different results.

You're right.....this image was alot brighter than the one I used the other day. If every image engraves differently, we may never get to the point of standard settings.

[Steve Clarkson]

Steve,

Run this one through. Choose Stucki. Set your speed to about 43.
I'd be interested to see what it looks like alongside your other ones.
I haven't processed it through photograv, I haven't altered the dpi
setting, all I've adjusted is contrast and brightness. I ran a test here
and it came out extremely well.

Thanks for reminding me.....I meant to run a test with Stucki, Jarvis and the other guy. I'll try it later today. Speed of 43 or Power? If 43 speed, then what power?

[Frank Corker]

Speed of 100 power of 43. I'm guessing on that power Steve.

[Steve Clarkson]

You guessed pretty good....because yours blew mine away.

I re-engraved my two best from yesterday, then yours, then three others that I was messing around with.

My two best almost look like caricatures (who am I kidding, I can't even get THOSE right!). The only thing I didn't like about yours was the background. I think if you had made it black, her hair would not have gotten lost in the granite.

Actually.....I think I forgot to pick Stucki.....so I'll do it again.

So.....are you going to teach me how to fix the contrast and brightness so I can get close to what you did?

[Frank Corker]

Good way to describe the difference, in fact it is the same thing I said, the differences are amazing. With the Epilog driver on it's own, a picture. Regarding the contrast Steve, just take it into any editor, increase the contrast and darken the picture. The one that I posted is still just a picture, to see just how dark I made it, make it back into a positive.

[John W. Love]

hmmmm...wait...you are darkening the picture??? Dang it don't tell me I've been doing it all wrong lol...I've been lightening the pictures considerably...and adjusting the contrast

[Margaret Turco]

OK, I just took Steve's original picture and tried to duplicate what Frank got. Converted to grayscale, adjusted brightness, contrast, intensity. Then in Effects, adjusted Tone Curve by grabbing near the middle of the curve and pulling down a little. It made the middle darks darker and came out pretty close. When inverted, those tones will be lighter than they were before. This has helped me a lot!

[Tim Bateson]

I don't think Fank literally meant that the picture should be darkened. Adjusting the contrast gives you a wider variance between the light and dark areas. As I've stated before contrast needs to be high on Granite as the subtle gray areas will be lost in the engraving.

[Frank Corker]

Tim, no I did mean it needed to be darker. The contrast is put up and the brightness has to be brought down. The Epilog driver seems to need it. It looks a little uncomfortable doing the picture, but it does do the trick.

[Steve Clarkson]

So Frank......you don't touch the tone curve?

Margaret, that's interesting that you adjust your tone curve that way. The photograv book shows almost the exact opposite! They suggest going about 1/3 up and pulling it NW and then going up to the 2/3 spot and pulling it SE.

Here are a few more tests...both pictures are the same.....but when I scanned the second one, I increased the brightness so you could see the detail better.

The first photo is Frank's picture with the same settings (100s 43p), but I changed the background to make her hair more noticeable. The second photo is Franks. The third photo is the same as the first....at the same settings (100s 43p).....but with my 1.5" lens! Yes! I finally pulled it out of the box! It appears that its a little more powerful than the 2" lens, so the fourth picture is the same as the first, but at 100s 30p. It looks just like the 2" lens at 100s 43p.......

When I put in my 1.5" lens.....was I supposed to change anything in my computer to let the laser know there is now a smaller lens in there?

[Scott Shepherd]

When I put in my 1.5" lens.....was I supposed to change anything in my computer to let the laser know there is now a smaller lens in there?

Focus level should have changed by 1/2" or so.

[Frank Corker]

As far as I am aware with the shorter lens, it allows you to get a finer detail so it may well be that you could go 600 or 1200 dpi and a smaller picture. Whether the granite could take the explosion I'm not so sure. But anyhoooo if you get bored with that new lens Steve, you can send it to me, they are hellish expensive over here.

[Tom Cole]

the focus level on the epilog mini does not change from the 2" lens to the 1.5" lens. the lens carrier itself positions the lens so the focus point on the table is the same for both lens carriers. all you have to do is change the carrier and burn away!

[Martin Boekers]

Steve,

What testing you did is what I used to do for years in the photo industry we called the "Test Strips" duh.

What I suggest is when you have and image that engraves well save that so it's easily accessable. That will be used as a benchmark (make sure that this was just a corrected B&W image before any adjustment through Photograv or halftoning)

Try to make the new one look as similiar in contrast & tonality as you can.
This should get you in the ballpark.

The laser is just like a camera and film, except cameras whether digital or film are much more advanced than the laser. They have settings that can correct your exposure automatically. Making the photo look good under a variety of conditions. The laser on the other hand is like using a manual camera. You have to hand set the focus and work out the speed , power and frequency. These are similar in functions of the camera's shutter setting, aperature, sensitivity and syncronization.

Just like a camera if you settings aren't right you image degrades.

Photographs do have a wider latitude for error then the laser though.

Hope this helps.

Marty

[Belinda Barfield]

Thanks Mad Scientist Steve, and others for sharing all this great info!

[Devon Jones]

this is semi off topic but not really.

i am using the gold method action on my photos (because i do not have the money to buy photograv) and i have decided to try a pic of a white tiger on black granit. i understand why you have to invert the image but do not understand why the action also flips it or mirrors it. does anyone know if you have to or why the action does this. thanks

[Frank Corker]

Devon, that was my fault, I originally intended the main use for it to be used with mirrors. You can just flip it horizontally after you have placed it, but do not resize it because that affects the image. I have sent you a PM (Private Message).

[Devon Jones]

well here was my first try. 100 speed, 42 power, 600dpi and on a 12x12 piece. the right side looks a little faded for some reason but other then that for a first time i think it looks ok. i would love to have it look great though. i used the gold method action to process the image.

[/URL]
http://img264.imageshack.us/my.php?image=imgp2762q.jpg (http://img264.imageshack.us/my.php?image=fullpic.jpg)
this is the full pic

[URL]http://img4.imageshack.us/my.php?image=imgp2765.jpg
this is the right side (not faded)

http://img264.imageshack.us/my.php?image=imgp2763.jpg
this is the left side (faded)

[Tim Bateson]

Looks good Devon. Did you try various settings? The fading may be due to too much power. Have your tried it at 300-400 DPI?

[Marc Myer]

Also, check the table bed alignment. Seems that granite is more sensitive to focus, and if the surface is not perfectly level, it will cause fading.

[Frank Corker]

Devon. Reasonable first attempt. Your power settings are too high which is why you are getting the obliteration in the highlighted areas. Lower the power to around 22/30 with 100% speed. You have a high powered machine there, at the moment it's just gouging.