Need a little image help

[Albert Nix]

I have to do some plaques for the local Chamber and they want the chamber building engraved on the plates that I use on the plagues if possible. I am using AlumaMark for the plates.I have a pic taken with an 8 megipixel camera so I have a decent image. But where is the best place to start. Do i open it in corel and change it to black and white or will gray scale work better. Or would I be better of to open it with photo grav. I need as sharp out put as possible. This is the first and I hope not the last work for the Chamber so I need to wow them. The finished image will be around 5" x 4". Would a small lens work the best? I will try to post the picture. Any help would be appreciated.
Thanks Al

[Bill Cunningham]

Hi Albert.. That image will not really resize to 5x4" unless you distort it.. Here it is in a photograv .bmp sized 5x2.3 (natural size) 300 dpi The original is converted to 8 bit gray, resized, enhanced, then run though protograv (cherry setting)
.. Don't do photos on Alumamark at a higher res than 300 or they turn muddy, mark with your focus off (up) by 1/8"
Don't resize the photo in the attachment or it will go bad..

[Albert Nix]

Thanks Bill. Did you take take the image straight to photograve or another software first? When I set photograv up I used 300 dpi as a standard setting. I keep hearing do not change dpi unless you us multiples of like 150,300,600 and so on. My driver only supports 200,250,300,500,600 then I think it jumps to 1000. So if I drop the dpi from 300, it will not be good right?

[Bill Cunningham]

Your picture was 72 dpi and big, so I took it to photopaint, (image button) re-sampled it to 300 dpi, and resized it to 5" wide, (the 2.3 high was the result of natural resizing..) I then converted it to grayscale, and under the Adjust button, chose Brightness/Contrast/Intensity, and manipulated the sliders until I found it pleasiing (gut feelings), then saved as a .bmp (I use the old photograv) and ran it at 300 dpi (cherry setting) This was just a very quick conversion, I'm sure if you play around with it, you will be able to improve it greatly.. I think the new Photograv will accept .jpgs for input, but be aware, eveytime you work on a .jpg, AND resave it as a .jpg, it will get crappier and crappier with every re-save.. If the customer gives you a .jpg, Use it only 'once' for the input, and never save it as a .jpg again.. The actual engraving file will 'never' be a .jpg, there is no such thing as a black and white binary .jpg..

[Bill Cunningham]

Thanks Bill. Did you take take the image straight to photograve or another software first? When I set photograv up I used 300 dpi as a standard setting. I keep hearing do not change dpi unless you us multiples of like 150,300,600 and so on. My driver only supports 200,250,300,500,600 then I think it jumps to 1000. So if I drop the dpi from 300, it will not be good right?

I forgot your main question.. ha.. comes with age I guess..
Yes only use multiples for binary files .If the binary file you create in photograv is 300 you can etch at 150/300/600/1200 etc.. If you use a odd setting, you will get banding or some other weird artifacts.. Photos in Alumamark should be etched at 300 dpi .. Try a few scrap pieces until you get the settings for your laser right..

[Larry Bratton]

How do you enter that building? I don't see any doors.
Albert, just my two cents worth here, when you shoot a picture with a digital camera, for the purpose of graphical use, always shoot it as large as possible. Also, as Bill said, if you can save it in anything other than jpg, do so. JPG is what is referred to as a "lossy" format and everytime you save it, it loses more data. 72dpi, as your image is, is fine if your only going to display the image on a computer screen. You'll want to get it to 300dpi if your going to engrave it. Although Photograv 3.0 will convert color to greyscale, I always start out with any image in Photoshop and change the Mode, size, and do any adjustments there. I usually save as a TIFF format, as it maintains all the data and it ready to use in Photograv. If you don't have Photoshop, you can do the same functions in Corel Photo Paint which comes as part of your Corel Graphics Suite. Good luck.

[Albert Nix]

Thanks a lot guys. I this is a long learning curve for an old auto mechanic lol but I am getting there thanks to guys like you.
Al

[Richard Rumancik]

. . . but be aware, eveytime you work on a .jpg, AND resave it as a .jpg, it will get crappier and crappier with every re-save..


. . .Also, as Bill said, if you can save it in anything other than jpg, do so. JPG is what is referred to as a "lossy" format and everytime you save it, it loses more data. . . .

I am aware that jpg format uses compression to reduce file size, but what I have often done when re-saving a jpg after minor editing is to set the compression to zero on subsequent saves. (When you save a jpg, PhotoPaint allows you to set the compression level to zero as well as adjust "smoothing".) I have found that with the zero compression setting the image does not seem to degrade. The file size does not reduce either which seems to support this theory.

Although for major editing converting to tif might be a safer approach, the file sizes can get very large (>10x the size of a jpg). I think you can get away with minor jpg edits as long as you don't keep compressing. Some programs might not allow you to turn off compression.

[Tim Bateson]

Albert, What brand of laser are you using?

[Albert Nix]

GCC MII 40w.

[Richard Rumancik]

Albert, what is the size of your "good" photo (in pixels)? The photo posted only shows the second floor of the building - is this what you want to laser? You can find out the size in PhotoPaint by clicking on Image -> Resample and then viewing the current specs. (Change it to display pixels instead of inches if needed.) Then you can exit out without actually resampling. Or do File -> Document properties.

To answer your question at least partially - you want to convert it to grayscale in PhotoPaint, not black and white. PhotoGrav needs a grayscale input. Probably the safest is to save as a .bmp (older version of PhotoGrav only accepted .bmp formats.) Often, after converting, I will lighten the image using Image ->adjust ->tone curve. You can lighten it by tugging (dragging) on the straight line. How much to lighten takes a bit of experience. Also it may depend on the material. I would do any cropping, mode change (to grayscale) and any other fixes in PhotoPaint.

If you want 300 dpi: I would take the 72 dpi file and "resample" to 300 dpi but make sure the size or number of pixels does not change. (The resampling dialog box will tell you original size and new image size. Resampled size should be 100% of original and the size of the data file should not change in this step.)

Save copies of the file as you go with different names (building_a.bmp, building_b.bmp etc.) so you can backtrack if needed.

You need to resample again to get the optimum final size. This is a real resampling of the image.

My camera generates an image with the following specs:

2848 px by 2144 px
39.5555" x 29.7777" at 72 dpi.

After "resampling" to make the image show at 300 dpi, the specs would be

2848px by 2144 px
9.493" x 7.146" at 300 dpi

Note that the number of pixels did not change in this step as the data is exactly the same.

Then I would try to figure out how to make a 9.493" x 7.146" image into a 5" x 4" image. Probably what I would do is resample at 50% to get an image of 4.746" x 3.573" image. If this is not "close enough" then you could try a different % but you may get some image degradation. It is best if you can resample 25%, 50% etc, even 33% or 60%, 80% often works well enough even if it is not "recommended". You have to experiment. If you plot on a laser printer it will give you an idea if the quality is suffering during the resampling process. I have had to resample images for publishing (newsletter) and you can sometimes get away with resampling values that may break the rules.

When taking the pictures it is often a good idea to shoot several at different distances/zoom so you have more choices to make the re-sampling "work" well with a nice fractional resampling value.

For some materials 300 dpi is too high. For marble and granite I think a few people have recommended 200 or so. I don't know about AluMark.

[Larry Bratton]

What Richard said :). All good advice. When performing those re-samples, be sure your software is set to "proportional".

[Albert Nix]

Thanks all. You ever heard leave well enough alone well I think I need to.
I learned a lot from all of the advise. I went back by the building this morning and took a better picture while the sun was in a better spot. Loaded it on the computer, imported to photo paint, adj. to 300dpi, resized, cut out some unwanted background, adjusted light/dark--contrast--intensity and saved as tiff, opened in photograv and save two images one for cherry and one for alumamark.
I then imprted into lasermaster and after a few test pieces ended up with the following driver settings--manual color fill--300dpi--90s--20p and used the 2" lens.
I am posting a scanned image of the last test piece. I think the detail turned out pretty good. The final size ended up needing to be 3" x 1.9". And like most scanned images the real one looks even better
Thank again guys.
Al

[Bill Cunningham]

Yup!! that look pretty good, AND there is a lot more building in this picture than the original posting..:D

[Larry Bratton]

Albert:
You follow directions well! Looks good (and now it's got doors too!)