Black marble test

[Alan Young]

Well I tried to engrave a photo on black granite as a test. I used settings of 35 p and 70 s and 250 dpi ppi Auto. IT came out OK but it looked like little dots on a grid pattern. I guess this is called dithered? My goal is to have it come out like Jerry Allens', Nice work by the way. I placed it in Corel draw and sent it to the laser using black and white mode and a 4x4 dithering pattern (this might be my problem) I have a mercury 30 watt laser. I did not use Photograv because I do not have it. Any advice on doing this will be appreciated.

Alan

[George M. Perzel]

Hi Alan;
Use Error Diffusion setting, not dithering. I've had my unit for 2 years now and still can't figure where to use the Dithering settings! You should get decent results even, without Photgrav, but may have to play with the brightness and contrast a little in Photoshop or another photo editing program.
Use Jerry's setting which have been posted before as he has the same unit you do.
George

[Kevin Huffman]

Hey Alan,
Yea, you should use the Error Diffusion or change the 4x4 to 8x8. Either one should get rid of those dots pattern.

[rich shepard]

Hi Alan
Convert your photo to 8 bit Greyscale not black and white,it should work better that way. The laser will pick up on the grey tones better that way
good luck
rich

[Alan Young]

Thanks for the advice. On my driver there are the options to use black and white mode of manual color fill. I have convereted the image to gray scale in photo shop and then imported into Corel draw. If I select manual color fill on the driver then the raster tab becomes inactive. Thus diabling the error diffusion so I do not think I want to use this by your advise. You mention brightness control do I want it to look what you might consider perfect or is one side better for output (brighter or darker). Also I fail to mention that I was inverting the photograph is this correct? I have it on a black background that I want to remain black. I can post the file but it is 2.7 megs.


Alan

[Kevin Huffman]

Hello Alan,

Manual color fill is if you are using different colors to obtain different depths. But these have to be a vectorized image, it can't be a bitmap. If you draw a green square, a blue triangle and a yellow polygon, in manual color fill you will be able to set different power/speed settings to achieve different depths.
When working with a photo on marble, you will want your color mode set to Black and White. Refer to post http://www.sawmillcreek.org/showthread.php?t=19358 for a better explaination of photographs.

Normally a little lighter is always better (in my experiences).

You are doing the right thing when inverting it. Marble is oppisite of most other materials, it turns white when engraved. Most others get darker.

I don't think you can post a file that large.

[Alan Young]

Thanks Kevin, I will try some more tonight. Am I correct that the image will not look as good on solid black granite as a posed to solid black marble? I believe I read some where that marble will give a better white to black contrast.

Alan

[Jerry Allen]

Alan,
Sounds like you pretty much had it right to begin with.
Some more info that you might find useful:
Black marble is a two color medium, black and white. You can change it only by creating white dots, or vectors lines. To do a picture, you want tiny dots that are arranged to give the illusion of shading. That's what the screens are for and what Photograv does for you. I will be disucussing Corel PhotoPaint here, but the same ideas apply to PhotoShop, etc.
Load your photo into Photopaint. Go to the Image menu/Color mode and change it to grayscale if it is not already. Clean it up and take out distracting background or dust and dirt specs, etc. From the image menu use the Brightness, Contrast and intensity tools to jack up the contrast which will generally help with marble. We'll test it later.
Do your resizing and cropping and set the resolution to 250 or 300 DPI using the Image menu/ Resample and the Crop tool.
Grayscale is not going to engrave well on marble because you cannot get more than one depth and one color--white pits, so go back to the Image menu when you are done cleaning and sizing and change the Color Mode to Black and White, one bit which is basically what you did except you chose the wrong screen. Try using the Floyd-Steinberg or Stucky screens and adjust to between 75 and 100 %. You will have to zoom in and out to see what changes are taking place. A few dots here and there can make a lot of difference. When satisfied, click okay. Make sure you have resampled before changing modes. Start over if you decide to resize or resample because the dots will get messed up.
At this point, go to the Image menu/Transform and you can invert the photo. Check for stray white dots and toggle back and forth, zoom in and out, to make sure everything looks good. Then save the file in the negative form. That's the one you will import into Draw.
When you finally get it into Draw, make sure you set the resolution on the General Tab to the same or a multiple of 250 or 300 in the Mercury driver. Don't mess with the grayscale settings because you are just burning white dots. On the Advanced tab, set the laser to burn bottom to top. Set your black pen to somewhere between 25-35%S and 70-80%P.
Don't resize or scale the bitamp in Draw. If you want to change it go back to PhotoPaint and make your changes. You can add some borders in vector and/or bitmap using Draw.

[Alan Young]

Well I tried what you suggested and have a couple more questions. After I edited and changed my drawaing and then converted it to a 1 bit black and white image it looked all black on the monitor. Now if I zoomed in I could see the dots and at certian zoom levels it did not look to bad. I have not burned it yet but is this normal. Second, What is your take on PhotoGrav? , I would think one should be able to do this as you have suggested but it does seem to take a lot of minipulating to make it work. I have no problem purchasing the software if it will indeed save some time. Alan

[Jerry Allen]

Alan,
I don't know what kind of monitor or resolution you are using. But generally speaking, I would say there is some point where you should be able to recognize the photo either by looking at it in it's positive or negative version. When you zoom in and can see the dots clearly, you should be able to make out an eye, cheek, or some king of detail that lets you know you got it right. Adjusting the percentage for the black and white filter either adds or deletes detail in the photo. Kind of something you just have to learn to understand, but you should be able to see the overall components when you view the whole thing, even though the dots will be distorted and it might look too dark.
Photograv does save a lot of time, but is not cheap. And, junk in, junk out applies. You still have to clean up a photo to remove busy backgrounds, dust, etc. It is just efficient at one trick which is to apply the one bit filter and uses a lot of calculations to do so. It is not foolproof and will not eliminate the need to have a good photo editor.

[Alan Young]

Jerry thanks for all your advice along with all the others. I have spent several hours tweaking and re tweaking my picture and think I have it to where it will work. At least as a test run on some scrap. I agree that the picture will only be as good as the one you start with so a good photo editing software is a must. I use Photoshop but am starting to get used to Corel photo paint. I found for the black granite which I bought a Lowes 70s and 15p, 200dpi and 1000ppi gave me the best results. I have some text I added in Corel Draw but at those settings it come out a little faint so I just painted with a little silver leaf and rub off the excess and it made it stand out better. I will post a photo when I do the final piece. My plan was to do this on black marble but the granite looks pretty good.

Thanks again to all the sawmillcreek users. Your help has been invaluable.

Alan

[Alan Young]

I am trying to post a picture but it will not upload. Any idea's? file size is under 1 meg.


Alan

[Shaddy Dedmore]

Couple things... you can zip it, and have people download it and open it... you can resize it so it fits, or you can find an alternate place to upload it then link to it.

If you want... I have a website where you can put up a pic, you cant really have people browse the gallery (I'm keeping the traffic down) but you can hot link to it from this site...

http://theoak.shaddysengraving.com/photo/

I have a tutorial for a different forum on the home page, but the basics still apply. After you figure out the link to your large pic, there's a "insert image" in the tool bar above where you can instert the link and the pic will show up like normal here.

Register your name, check your email to initiate account, create album, upload pic, look for pic and find out address of it, then post here... there are step by step details in the tutorial...

Members of this group can use it, just don't get carried away. :)

Shaddy

[Jerry Allen]

Alan,
I know this info must be around somewhere and I think there is a Help forum. But who has time to read the manual?

Here's what I know:
First of all the picture should be less than 500mb, I think, and that's still pretty big. Use Photoshopor Photopaint to resample to 96 DPI and about 5" or less in the greatest dimension. Then use .jpg and compress it 10-20% when you save it. That should yield a file in the 50kb or less range, which is efficient for opening the thread page, and saving space on the server.
When you click on reply choose "Go Advanced"--you probably knew that.
Don't ever click Preview Message while you are editing. Just Submit and fix it later if necessary.
I suspect your file was just too large.

[Alan Young]

Well I don't know what was harder,doing the engraving or trying to take a photo of it after it was done. This picture does not do it justice but you can get the idea of the photgraph engraved in black granite.

Alan

[mike wallis]

Looks good Alan. I've been trying to refine the granite as well and have some granite from Lowes also. Did you do any paint fill on the photo or is the contrast naturally that good? Also what power and speed settings did you end up with?

[Alan Young]

I did add a fill to the letters I used a liquid silver leaf. I applied it with a q-tip and then rubbed of the excess. I did a couple of lines at a time. The photo is untouched after I engraved it . I found that a lower power setting made the best engraving. The higher the power the less detail showed up, it almost was like it made too big of dot with more power. My final setting were 70s and 15p, 200dpi and 1000ppi .

Alan

[Al Curatolo]

Another thing that I've found works is to keep the image as greyscale through the entire process. Darken it significantly in photopaint and then cut at a higher power in coreldraw. Let the driver convert/dither at 300 dpi. With a 35 watt laser I cut with 60% speed, 40% power on granite. I never convert to black and white throughout the process and although I have Photograv I find that I do a better job prepping the image than it does.

You can see my results in the gallery on my website.

Al
http://www.handsonimaging.com

[Alan Young]

Excellent work Al.

When you do the glass are you mirroring it on the back side? I do not have photograv but do use photshop and photopaint.

Alan

[Al Curatolo]

Yes, I do mirror it and cut on the backside, it diplays nicer that way. When the piece is complete I usually mount it in a frame and then put another piece of glass on the back to protect the paint so what you really have is the paint sandwiched between two panes of glass, make sense? Just mount in a regular picture frame using glazing points...

Al

[Al Curatolo]

Just an FYI for glass:

The first piece you cut is guaranteed to look like crap, don't be discouraged. Your image will probably look over-exposed with no detail, just darken the photo in your software of choice and remember to invert your image so that it is negative before cutting.

Al