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View Full Version : Banding - why?



Steve Busey
08-21-2012, 6:08 PM
Been trying to laser a good pic on this black marble - finally got the face density the way I wanted it, but now the top of the sleeve, which is VERY WHITE, shows banding when I burn it. Any ideas as to the cause and/or fix? There's no banding in the graphic, none on the "face" along the same latitude. Seeking your collective wisdom...

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Thanks...

Steven Cox
08-21-2012, 6:54 PM
As you say the sleeve is very white whereas the face area has varying tones hence doesn't show banding. Try doctoring the sleeves in Photoshop and tone it down and or use the air brush tool and add in some ripples in the fabric areas to help give it some variation.

Scott Shepherd
08-21-2012, 7:35 PM
First, that's granite, not marble. It's sold as marble, but it's granite, in my opinion, from seeing the photo. Second, that's very odd for banding. That's horizontal banding. Vertical banding is common in this situation. I can't tell you what the answer is to fix it, other than follow the directions of Steven and edit the colors on that, it's too white and give that a try, but I'd check a couple of things. First, how are you processing this? Are you using Photograv or just hitting print on the photo and letting it engrave?

If you're doing that, to me, I personally believe that it's critical that your engraving resolution matches your photo resolution. Check your photo resolution and see what it is (Pixels divided by size will give you the number), for instance, if you have a photo that's 3000 x 2000, and it's 9" x 8", that would be a DPI of 333. You wouldn't want your laser set to 600 because there would be a mismatch, which, in my opinion, can cause some serious issues.

Second, don't process or send the photo over at more than 250-300DPI. It looks like you might be set higher than that because that photo is really blown out. I don't recall how that works on the Epilog, but set it at 300 if you can and try that.

Third, don't overpower it. It doesn't take a lot to give you a good image. The difference between 100% power and 40% power might not even be visible. If you overpower it, you can get issues as well. Not saying that's causing this, but I'd make sure I wasn't overpowering it.

Unpredictable results can be caused by all of those things listed above. Once I had them all dialed in, I'd have a better starting point on figuring it out.

Hope that helps some.

Can you list your photo size and also the pixel size of it? Then let us know how you're processing it, and it what program.

Steve Busey
08-22-2012, 12:42 PM
First, how are you processing this? Are you using Photograv or just hitting print on the photo and letting it engrave?


Original scanned at 300dpi, brought into photoshop, cleaned up bkgnd, converted to B&W BMP. Run thru PhotoGrav, then imported to Coreldraw, printed at 300dpi. Engarving size matches original scan size (6.88" x 4.xx").


Third, don't overpower it. It doesn't take a lot to give you a good image. The difference between 100% power and 40% power might not even be visible. If you overpower it, you can get issues as well. Not saying that's causing this, but I'd make sure I wasn't overpowering it.

I'll take a look. Was using recommended 25S 100P for my 35W laser. Don't have the system in front of me, will check again tonight.

Thanks for the input - any other insight out there?

Cindy Rhoades
08-22-2012, 4:08 PM
Have you tried cleaning your lenses and mirrors/ I had the same issue a couple of different times and I had missed cleaning my mirrors. The second time I recalibrated my beam because it was off a little bit so it went out of focus the further down the piece I went. I use a lot different settings for marble and granite on my epilog 45 Watt Mini 50 speed 40 power at 150 - 200 dpi. My original artwork is at 300 dpi

Steve Busey
08-23-2012, 9:26 PM
Check your photo resolution and see what it is (Pixels divided by size will give you the number), for instance, if you have a photo that's 3000 x 2000, and it's 9" x 8", that would be a DPI of 333. You wouldn't want your laser set to 600 because there would be a mismatch, which, in my opinion, can cause some serious issues.

My BMP is 2064x1464, the image is 6.88" x 4.88", scanned actual size at 300 dpi. It was lasered at 300 resolution.

I tried to post it here, but it won't upload (size limitation??) :( - so here's just a portion showing the sleeve area.

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Steve Busey
08-23-2012, 9:27 PM
Have you tried cleaning your lenses and mirrors/ I had the same issue a couple of different times and I had missed cleaning my mirrors. The second time I recalibrated my beam because it was off a little bit so it went out of focus the further down the piece I went. I use a lot different settings for marble and granite on my epilog 45 Watt Mini 50 speed 40 power at 150 - 200 dpi. My original artwork is at 300 dpi

I guess I'm due for a cleaning & lower power test this weekend...

Scott Shepherd
08-23-2012, 9:40 PM
Steve, I think it's due for a call to Epilog. Horizontal banding is not very common and there is a cause for it. I once saw a service document that explained various problems and I know banding was broken into horizontal and vertical. The solution was different for each and I don't recall what it was. It's been years since I saw it.

I'd call and email those photos to Epilog. If anyone can help quickly, it will be them as I'm sure they will have seen it before.

Wish I could help, but I'm stumped.

Let us know the solution. It's really got me scratching my head.

Chuck Stone
08-24-2012, 2:01 PM
Can you try a small part of the file again at lower res?
it would be interesting to see what happens if you crop the photo and resample at 200dpi,
then engrave at 200dpi. I wonder it if would go away

Steve Busey
08-24-2012, 3:13 PM
Can you try a small part of the file again at lower res?
it would be interesting to see what happens if you crop the photo and resample at 200dpi,
then engrave at 200dpi. I wonder it if would go away

Worth a shot. I hope to do some more testing this weekend, but am running out of test pieces, so am looking for all the great ideas I can get!!

Chuck Stone
08-24-2012, 5:50 PM
any little corner of a piece that was already discarded will do nicely..

Mark Sipes
08-24-2012, 6:19 PM
Don't need to laser the entire job, just cover up the upper portion with white bars. Layout the full size (300, 200, 125 dpi) and relaser as described above to see if the white banding section is corrected.

Steve Busey
08-25-2012, 2:44 PM
Epilog told me to "manually focus" and try again. :confused: Worth a shot...

Steve Busey
08-26-2012, 6:52 PM
Epilog told me to "manually focus" and try again. :confused: Worth a shot...

Well, I tried three things at once (since I was down to just a few corners of testable material...).



I went from 25% speed to 15%

I went from 100% power to 50%

I manually focused on the sleeve portion of the engraving.

(OK, four things...) And I did the engraving from the bottom-to-top, in case my laser tube was getting old and weary by the time it reached the high intensity part of the pic. Aside from the sparkle from taking this flash picture, all is well. Until the next adventure. Thanks for everyone's input!

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