Photographs on wood - need your advice folks... (using photograv)

[Harry Radaza]

I bought my Universal VL300 50 watts 6 months ago. Upon opening my shop I went into a thousand different directions. After a few months of playing around we focused on two things -

1) gift items on wood with photo engravings and text
2) industrial engraving / cutting of different materials for the fashion industry (for export)

Needless to say, #2 has done us some pretty good business; while the photo engravings on gift items (#1) has really taken off and we have since added a second machine ( Laserpro mercury 25watts)

We are anticipating more photo engravings on wood as the holiday season approaches and we are opening another satellite branch.

The problem is this... I bought Photograv months ago and followed the instructions to the letter. We get excellent results but only AFTER processing the BRIGHTNESS/CONTRAST on Photoshop. This photoshop process alone took at least 20 to 30 minutes. And still we were not exactly guaranteed results. Sometimes the engraving would come out burnt.

I have since read others in the forum saying that in photograv it was point and click and no other external adjustments needed. Is this true? Am I wasting 30 minutes for each photo job (at least 10photos a day) ? If so how am I able to achieve those results without adjusting in photoshop?

And while we are at it, how do I find out what the optimal settings is for my laser for wooden photographs?

with the holiday season onslaught coming up, I want to be able to open the file, resize it and orient it correctly, process in photograv, open in corel and print! however, right now we are having to process in photshop for 30 minuts sometimes up to an hour if bad picture, then process in photograv, and still not get guaranteed results.

How are you guys able to do it?

What am I doing wrong ?

Tell me what I need to supply ( laser settings, photograv settings etc ??) so you can help me.

BTW, I followed the Tone Curve settings that was suggested in the manual but did not work out for us. Would come out too dark or too light depending on the picture.

[Rodne Gold]

It's basically point and click , provided you realise what the laser does to wood to create the image. If the laser worked "properly" on wood , you would get a real clean engraving with almost no contrast. To engrave wood the laser actually has to rely on a heat affected zone that actually "damages" the substrate rather than vaporizes it -IE it burns the wood or burns the resins contained in it.
However one has to realise the laser is representing shades of grey using a single colour , the burn mark. These burn marks have got to be clumped and the spacing between burn marks fools the eye as to a shade of grey. Problem is , the laser is affrecting a whole lot more than just the spot its supposed to vaporise , IE its affecting adjacent areas. the common mistake folk make it to have too high a resolution both in lasering and scanning. The spot size of a laser using a 2" lens makes it impossible to achive a resolution of 300 burns per inch unless the burns overlap. the fact that wood has dot gain (dots get bigger than the laser spot size) makes this even more problematic and using a high dpi when lasering and a high dpi with scanning results in a very messy "overburned" picture. the delicate shades of grey will not come out. Add to this the fact that wood has a grain , ie a non smooth surface which makes it even more difficult to hold a resolution (kinda like trying to speckle blotting paper with fine droplets of paint , the droplet wont hold its shape and will soak into the blotting paper to create a much bigger paint mark than the droplet is , making for a messy picture)
So to put it in perspective , when using wood , tell photograv you are using a laser with a bigger spot size than you actually are and tell it you are using a low dpi - I would suggest 200 dpi.
When scanning , scan at a high ppi resolution but after resizing the pic down to the engraved size , then REDUCE the resolution to 100 pixels per inch or so - DOWNSAMPLE the image. You want to lose info.
Photograv will represent the "engraved image" as little black specs with variable spacing, If this spacing looks too dense on screen , it is. So the strategy you need to adopt is to have a "grosser" image in terms of the dot spacing , more like a poorly printed newspaper image than a fine black and white photo. As I say , the major problem is the resolution the media and the "printing" process can resolve and unless you get that right , you have very little chance of getting the best results regardless of what substrate you use.

[Dave Jones]

I can't imagine adjusting contrast/brightness in Photoshop taking 30 minutes, unless you are using a 386 and Photoshop 3.

If the original image is large, resize it first and then adjust the brightness, contrast, and curves. I can prep a photo in Photoshop in 2-3 minutes, including starting the program, loading and saving the image. The actual contrast/brightness setting takes only seconds.

[Harry Radaza]

Rodney - thanks for the reply. will try your suggestions and hope it gives me a more consistent result in one process without having to do B / C adjustment.

Dave Jones - yes it actually takes us that long. and no I am not using a 386! we have learned that area's in the pic that are too dark will end up burnt on wood. These very dark area's remain dark even after adjusting B/C. So we usually have to lighten these dark areas to make it gray using photoshop (dodge tool ? or is it the other one ? ). Then convert in photograv. And after seeing the bitmapped or processed image we then adjust again if needed. We can tell from the processed image if some area's will end up being too dark when engraved.

I hope others can give us tips.

[Dave Jones]

Have you tried using the "curves" adjustment? It's sort of like a gamma control. It can shift the dark grays without affecting the light grays much. If you have several dark areas and only want to affect one of them, then you would need to select that area and adjust seperately. But if it's a matter of shifting the dark grays to be lighter, then curves might be a much simpler way to fix it. Lasers are non-linear, and the curves allows you to adjust the grays in an image to be non-linear. So it works well for lasers.

[Roy Brewer]

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We get excellent results but only AFTER processing the BRIGHTNESS/CONTRAST on Photoshop. This photoshop process alone took at least 20 to 30 minutes.

Harry,

You'll not get better details than those offered by Rodney, but I'll emphasize you should probably not be using Brightness/Contrast controls but rather the Tone Curve controls.

If you are using CorelDRAW, the new X3 Image Adjustment Lab allows you to adjust the Tone Curve without running a raster editor. I often use one of DRAW's error diffusion algorithms (Jarvis, Stucki or Floyd-Steinburg) "temporarily," to see how it looks (then undo and save out for PhotoGraV).

We typically, however, spend 4-8 minutes knocking out the background in PhotoPaint, so max time in raster editor shouldn't be more than 9-10 minutes. Also, I think we've all learned that some pics simply don't lend themselves to being laser engraved; I've started recommending to my clients that they keep a "portfolio" of photos which illustrate what will and won't "turn out" when laser engraved. This "portfolio" is helpful to "train" both customers and employees.

[Brent Vander Weil]

I don't have the funds to make the PhotoGrave purchase at the moment... does anyone out the use Corel 12 to Engrave photos? I would love to get some input on the techniques ans proceedures for photo engraving directly from Corel. Thanks in advance to all...

[Joe Pelonio]

Brent, use bitmaps, mode, greyscale to change a color pic to BW. Then use effects / adjust to manipulate the contrast, brightness, tone curve etc. None of that can really be explained in detail here, you'll have to experiment with it. I found these tools to be more work than using
photoshop but it can be done in a few minutes with practice.

[Brent Vander Weil]

Joe -

I have access to Photoshop... if this will make my life easier I will load it up and play with it. Thanks for the tip... When you scan a picture in should it be at high resolution B&W then crop resize etc.?

[Joe Pelonio]

Scanning software differs, but my best results are to scan in B&W mode
at 400 dpi and save as a tif. The file is big but the output is better. I don't
scan over 400 dpi for wood. For things like a photo of a face on a name badge or a photo on a tile or coated metal where a higher resolution output is going to look good I may go 600. One job I'm working on is antique photos scanned at 1200 dpi by the customer.

[Barbara Buhse]

Harry,

Before I reply to your post, I'd like to ask... how have you managed to get all that photo business so quickly? Do you have a store front? I have been trying to expand and find the craft shows slowly building clients, but not very fast...

anyway, in answer to your post,
Forget phtoshop (egads!) and get yourself something simpler just for processing the brightness/contrast on scanned photos... I use Microsoft Picture It.
I always turn to black and white first, THEN adjust brightness and contrast, usually increasing both, (In rare cases, not so). The photo looks much lighter than you'd want to print it on paper, but always comes out "normal" looking in photograv. Takes only a few seconds.

Barbara

[Rodne Gold]

Key to engraving photographs is the halftone pattern you generate , this is how the dots are clumped to represent grey.
Start with the scan , do NOT scan at anything more than 300 ppi (sometimes called ppi) if you are not going to enlarge the image for engraving , ideally you want 100 pixels per inch at the final output. At 300 dpi/ppi scans , you can effectively engrave at 3x the size of the original photo. Garbage in = garbage out - poor scans , poor photos etc cant really be fixed without a huge amount of post processing work. Get a top notch scanner and use the scan tools provided with it to remove moire etc - a good scan is what you need. DO NOT scan in colour , this will only serve to increase file size and will not give you a preview of what the greyscale image will be.
Insipid pics or pics with colours that approximate shades of grey will never engrave well , for example a medium coloured dog on a green grass background will have both the dog and the background approximating the same shade of grey , you need pictures with "POP" , the main subject MUST stand out against the background and be isolated from it. Large dark areas will be problematic depending on what you are engraving. Extreme detail will not engrave on some substrates.
In terms of adjusting brightness and contrast , overdoing this to make a pic engraveable will lose huge amounts of detail , should you wish to do this , you need to adjust shadows , midtones (18% grey areas) and highlights (bright areas) indivdually. Once you have an acceptably contrasty image (you need more contrast than if you are going to print) then the next step is to sharpen the image. For sharpening you use "unsharp" mask. The normal setting would be something like 300% , 1 pixel radius but for engraving , oversharpen , like 500% and a 2-3 pixel radius. what this does is define and isolate edges and will allow these to be engraved darker. Oversharpening in printing will make halos around the oversharpened objects , but whats bad for printing is good for engraving.
Once all that is done , resize the image to exactly the size you want it engraved and reduce the resolution to about 100 -150 pixels per inch (often called DPI) if you are engraving on a substrate that wont hold fine detail (like wood)
The final step is to convert the whole image to a 1 bit (black and white) image using one of the halftone algorithms , make sure that the distribution of the dots is pretty even and no "patterns" are visible , remember that spacing should look further apart on screen than you would think it should be as the laser has "dot gain" , the dots you see on screen will be a lot bigger engraved on certian materials than they appear and thus will tend to look closer together. You will have to fiddle with the various conversion routines to get this right for your laser
Bear in mind that on materials like acrylic , black engraving will appear white and thus the WHOLE image must be inverted.
You should also have a look at Corels powerclip function as you can define shapes and the shapes are used as clipping masks for the graphic , like you can draw an oval and place the bitmap in it using powerclip and only the oval and the bits of the graphic inside it will be output.

[Ed Lang]

I too have Photograv and am not getting results that are good at all.

Would it be possible for someone to scan a picture of something and make it available to us who are having trouble? Then those of us could have a known good picture to try and do the Photograv work on.

So how does Photograv tell my print driver what speed and power to use?

I just scanned at picture after reading this thread and I did get better results but they still look real bad. I think I am still missing something.

[Mike Mackenzie]

There are some important set-up features that you must do when configuring photo grave.

System type (Universal, Epilog, Etc)
Len's spot size (0.003, 0.005, Etc)
Max Speed ( Inches per second )
Turn Time (how quickly the system stops and starts this usually is set automatically once the system is chosen)
Laser wattage (25, 30, Etc)
Output resolution (1200, 1000, Etc. this is what you will engrave the final picture with.)

To do this open photograve click on FILE and then Preferences.

Make sure that these settings are correct.

Another note scan at the same resolution that you will be outputing (scan in at 250 DPI engrave out at 250 DPI) Also very important do not change the size of the processed photo grave image this will mess things up.

ED,

To get the suggested power and speed settings go to the INFO tab once everything is processed it will give you the suggested power and speed settings to use for the material you processed.

[Ed Lang]

Thanks Mike!
Here are my setting.
ULS 50W
Max Speed 25.0 inch/sec
Turn Time 0.142 sec.
Lenses .003, .005 and .007 I have a check in Always use .005 since I have a 2.0 lense and I think that is the right one.
DPI's listed are, 1000, 500, 333, 250 and 200.

The last one I scanned I scanned at 200 DPI on the scanner.

With a little more work and a few suggestions, I just might get this thing going.

Ed