Weird Photo Problem

[George M. Perzel]

Hi Gang;
I thought I would do a granite tile photo for a friend whose daughter is graduating- great photo, good resolution, should be a snap. Six hours later (yesterday) I finally quit banging my head against the keyboard and opted for an India Pale Ale, which greatly helps to quell my frustration.
See pics below.
In Photoshop, I took the original (Pic 1)(480 dpi-1.1M), changed it to grayscale, slightly changed the brightness/contrast , resized it to 300 dpi and 12x12 ", softened the lower edge to get rid of the hard line-maybe 5 minutes total. Saved it as a bitmap and opened it in Photograv with the granite prm and saved the engraved results (pic2) and imported them into Corel X4.
Being the cautious type, who has been burned many times before by what looks good may not be good, I opted to trial a section of the photo on a piece of black plexi scrap-results are Pic 3. Not good- horrible wide slanted lines across the face. Inspected the engraving bitmap at high magnification and can see no lines.
1. Thought it might be the material -nope, same results on wood
2. Tried a different granite prm in Photograv-no appreciable change
3. Tried inverting photo and used cherry prm-no appreciable change
4. Kept original size-300 dpi-no change
5. Had my first IPA to help me think clearer
6. Kept original size and original dpi (480) -no change
7. Tried another photo- no problem-no lines
8. Had 2nd IPA- gaining courage, we can solve this
9. Took original photo, only changed to grayscale and 300 dpi, then Photgrav with granite prm- no change
10. Being an engineer (retired) who is highly trained to solve problems quickly and efficiently, I gathered all the trial images and results and, with my third IPA, carefully analyzed the info and found nothing obvious- other than the lines seem to vary in angle and width from the first trial-Pic3 and later ones (Pic 4).
11. Said the heck with it and quit to watch reruns of Gilligan's Island (with another IPA).

I would certainly appreciate any advice, suggestions, ideas, thoughts, etc regarding this-really got me stymied.
Thanks, gang
Best regards;
George
LaserArts

[Frank Corker]

George sometimes reducing the size will result in a moire on your image, which might explain that banding. This might sound a bit weird, but I do it in the old windows 3.11 art package I use, I resize at 75% and then keep resizing 75% each time, until I am close to the dimensions that I want, then make the final adjustment to the exact size. It does seem to stop that type of thing happening.

[George M. Perzel]

Frank;
Thanks for quick response.
I tried it with no resizing, either size or resolution-same results. You did trigger thought. I recently upgraded Photoishop to CS3-will try it with CS2 and check results
Again, thanks
Best regards;
George
LaserArts

[Scott Challoner]

George

I had this same problem a few months back. It turned out to be the bearings on the carriage. There was a flat spot on one and it would hicup everytime it rolled accross it wich resulted in diagonal bands. Replaced the bearings and it went away. Try inspecting them. If that doesn't work, grab another IPA.

[George M. Perzel]

Hi Gang;
Would you believe the problem turned out to be the new version (CS3) of Photoshop??
Ran the same file the same way using the same settings/etc in the older version of Photoshop (CS2) and the lines disappeared!!
Didn't quite believe that could be true so reran the process in the new version- with the same bad results!
Now I understand why some folks are still running Windows 98. It is a major frustration to pay a lot of money for an upgrade and find its worse than what you had and there is really no avenue for recourse as you would waste a ton of time (and get even more frustrated) trying to explain the problem to some customer service rep in downtown Mumbai.
Scott- thanks for the tip. Thought of that early on but dismissed it after running other photos/jobs OK.
Now I have to go and restock my supply of Sierra Nevada IPA-so all is not lost!
Best regards;
George
LaserArts

[Dave Johnson29]

This might sound a bit weird, but I do it in the old windows 3.11 art package

Morning Frank,

Is that art package the one that came with win3.11 or is it 3rd party? I am running win3.1 and using Corel 5 which is clunky at best and frequently crashes with Font GPFs. Would you tell me the name of the software and I will see if I can get a copy somewhere.

Thanks

[Scott Challoner]

Now I have to go and restock my supply of Sierra Nevada IPA-so all is not lost!
LaserArts

I can also recommend Big Sky IPA. I like their Moose Drool Brown Ale too.

[George M. Perzel]

Hi gang;
Please ignore previous statement that problem was solved and culprit was new version of Photoshop.
I initially rejected Scott's suggestion (flat bearing) as problem did not appear on other photos- until you looked very close! Funny, as I just changed the horizontal carriage bearings a couple months ago as preventative maintenance-old ones were OK. Again the old adage- don't fix it if it ain'y broke!
Anyway, major investigation will get under way this evening-got a full case of Sierra Nevada so should be set.
Any other ideas still appreciated.
Best regards;
George
LaserArts

[Scott Challoner]

Hi gang;
Any other ideas still appreciated.

Try Dogfish Head IPA too.
But seriously... Measure the distance between the bands and figure out the circumference of one of your bearings. If they are the same, you have more evidence pointing at the bearings.

[George M. Perzel]

Hi Gang;
First of all, thanks to Scott Challoner for pointing me in the right direction ( and also for the IPA recommendation!).
After reviewing the test results, it appeared that the problem was speed related as the frequency and angle of the lines would vary with changes in the engraving speed. This pointed to a mechanical issue and the most likely culprit was the carriage. I had mentioned in a previous post on this thread that I had changed the carriage bearings about two months ago. Each bearing (see pic) are held in place by a bolt which is tensioned by a spring.
The bolts on each bearing were tightened down too tight, apparently causing the carriage to minutely skid rather than roll on a repetitive basis.

I adjusted the spring tension in stages, and watched the line width decrease and the angle change on the test results, until they virtually disappeared. In retrospect, the problem was not apparent before and was only visible on highly detailed photos- which I seldom do.

Anyway- thanks to all who offered help and advice.
Best regards;
George
LaserArts

[Mike Null]

George

Glad you have solved your problem. More importantly you've improved your beer as well. However, the best kept secret about beer is the St. Louis Brewing Co., otherwise known as Schlafly's. Try their IPA as well as their Kolsch (only brewed in St. Louis and Cologne, Germany.)

[George M. Perzel]

Hey Mike;
Thanks for IPA info- problem is that many of the small distribution out of state (NY) brands are tough to find here. This crazy state (legislature is currently locked out of chambers as they argue as to who's in charge) must have laws against import of anything which threatens a state industry-will check next time we go down to PA for a visit.
Best regards;
George
LaserArts

[Scott Challoner]

As long as your in PA, you may as well stock up on Yuengling too.

[Scott Shepherd]

As long as your in PA, you may as well stock up on Yuengling too.

I've stocked up so much, they send me Christmas Cards