Halftones (part 1 of 3)
Author: Christopher Haney
Revised: August 03, 2005
Let me start by saying, right of the bat...”Anything and Everything that can go wrong, will go wrong! The most important step in creating “halftones” is your own mind-set! Be determined and diligent and don’t give up...you “will” make frustrating mistakes.
With that said, let’s move on!
For a very long time glass carvers have been searching for methods to improve detail. Reproducing photographs has always been a challenge, even to the most gifted artist. With the introduction of “Photo-resist” to the industry it has now become possible for the less gifted craftsman (such as my-self) to create beautiful recreations on glass with all of the detail the original photograph has to offer. This technique is being referred to as Halftones. Halftone by definition is; “an illustration printed from a relief plate, showing light and shade by minute dots”. It is a very exciting addition to anyone’s arsenal of techniques and combined with your imagination...the sky's the limit!
This is a bit tricky...new improvements to techniques and equipment are being introduced every day. It’s difficult to say what’s best for any given situation. Get as much information as you can from other carvers who do halftone work and compare. I will list the equipment I use and what it is for. This is just a guide line, you can make any adjustments you deem fit!
1). HP 4050/Laser printer w/ PS driver (will discuss later in document) / 1200 res.
I use this printer to create my film positive.
2). 26-1K Mercury exposure system w/vacuum chamber. Approximately 25 inches Hg vacuum.
I use this to expose the photo film.
3). Karcher 330 pressure washer 600psi / modified to a short handle
I use this to wash the film
4.) Blow dryer / common house-hold / two settings - high heat / low heat
I use this to remove water from the film after wash-out (very important)
5). Film Dryer unit / four shelf
I use to rapid dry the film / 15-20 minutes
6). Custom built cabinet
7). Pressure pot / I do not recommend a siphon system for halftones
1). Ultra-Pro 3mil self adhesive film / no glue needed
2). Apollo clear film transparencies / non-striped / Number #CG7060
This is for the film positive
3). Krylon Crystal Clear spray
This is to enhance the film positive
4). 12” x 12” mirror
Used as wash board
5). Bankers clips / 5 inch
Used to hold film to wash board
6). Burnishing tools / roller and squeegee
7). 220 grit Aluminum Oxide or SC
180 will work, I prefer 220!
Corel Draw / Photopaint Version #9
Other photo programs will work just fine, check with others for details on different software applications. All the descriptions that follow will be for Corel Draw!
Note: If using Corel Draw you should upgrade to Version #9 or better...you will have problems in the lower versions. Radical changes were made in 9 and 10 to improve halftone conversions from Corel.
Below, you will find a step by step description of the method I use to create photographs on glass. It is a very long and involved process. However, when you develop your own method or system you will find that it can become a common routine.
Say in your mind “I will make a mistake” (LOL)
Select your image (photo) the better the quality of the picture, the better the results. Try and get the client to provide you with a selection. (Oh, by the way...good luck on that one!) What you are looking for is contrast, even balance and the “lack of shadows”. You will probably never find the perfect picture, but it helps to start with the least problems. Once you have selected the picture it is time to scan it into your computer. I use a color scanner set at 1200 x 1200. It takes longer to work with the finished file because it is so large. However, the detail is very helpful for the next steps. I usually scan in the color mode for more detail!
Now that you have the picture it’s time to start making changes. This is very difficult at first, because you do not know what to look for until you have seen the results from previous mistakes. This will come in time and with practice. The changes you will make will be the contrast, bright and darker. Whites need to be toned down and blacks need to be lighter. I wish I could say every picture uses the same settings...but in truth, every one is its own little monster. After these changes I then convert the picture to grayscale (if working with a color photo). Again make any adjustments needed. At this point I crop the picture, unless I have chosen to keep the background. This is between you and the client. If cropping the picture I will select the freehand crop tool from the menu and proceed to edit the picture. I do this at a very high magnification and am careful to follow curves accurately. A bad crop job will ruin even the best blasting job! When I am finished cropping the picture I copy it and then open a “New File”. Set the background to black (important step, because we will invert the picture later) and adjust the size of the file to the size of the glass that I will be using. (in most cases it is an 8X10). I then paste the cropped picture into the new file. At this point, I resize the picture with the dragging tool. An important step here is the copy and paste, when you do this step the computer treats the artwork as an “object” now when you drag the picture to resize it there will be no distortion. This is very helpful when resizing Vector-Art also! Now we have the cropped photo re-sized to fit the glass and it is on a black background. (important...save the file now!) Be sure that the photo is the actual size that you need...once you convert the picture to a half tone image any alteration will distort the dots...not good!
Now...to convert the picture (Corel Draw-PhotoPaint) you select the black & white setting under the image then mode menu. You will see a pop up window that lets you make selections & changes. Choose Halftone...then round dots...then 90 degree angle...and finally your dpi. I recommend in the beginning to stay low...around 20 - 25. This will let you see what it is suppose to look like. You can change this setting in the future as you progress with your ability. On this note...I would like to say that most of my halftone work is done in the 30 to 40 dpi range. The reason for this is volume...I do a lot of halftone work and have many samples that clients view. If some are at a higher resolution then others the client will expect it. The quality of the picture is very important when working with higher resolutions. Find a range that you are comfortable reproducing with confidence and you and your clients will be very happy! I have had several people come to me and say with their first or second try they achieved 85 dpi....that’s wonderful...now let me give you a normal picture that a client will give you for a fiftieth wedding anniversary that is fifty years old and give me that 85 dpi! The other reason that I do not work with such high resolutions is that the blacks disappear and the whites look like over blast. I strive for uniform dots...this gives the final work a sense of order and control. Most high resolution halftones that I have viewed appear to be sloppy craftsmanship! That’s of course just my opinion! Now we move on to the 90 degree angle verses the 45 degree angle. Some people prefer the 45 degree setting...I do not! Here’s why...your eyes (by conditioning) view objects a first glance horizontally (side to side) then up and down! The 45 degree setting puts diagonal lines in the image...I find this to be very distracting at first glance...however, you should try both and come to your own conclusions.
At this point you are ready to select the OK button...a pop-up menu will come up asking you if want to merge the image to the background...select yes...because this will smooth the cropped edges of the image and give you a much cleaner appearance on the glass! Now you can add words or borders or what ever else your imagination will allow!
It’s now time to print the “film positive” You have several options here. You can save the file to a disk and take it to a print shop that is capable of generating a “Genuine Film-Positive” which will be done on acetate or Mylar...this is by far the best method but very costly and not practical. The other method is to print your own, this is referred to as just a plain “film positive”. Before we continue let’s talk briefly about printers and drivers. Until recently you were limited to only using Laser printers to create a film positive that was black enough to handle the small dots of a halftone image. With the advent of a new product called Accuart from Photobrasive you are now able to use a standard ink-jet printer...however, with out the Accuart-film an ink-jet printer will not work well for your film positive. If you do not want to be reliant upon one product that can be rather expensive then you should invest in a moderate size Laser printer. Now we get into the issue of “Post-Script drivers” I just don’t know what to say on this subject! So, I will just tell you my experience...the driver is what reads the language between the computer and the printer...Post script drivers convert line art and halftones into readable information that the printer can understand. With out the PS driver your computer will not interpret the dots correctly...it will print, but what you get is not true to your settings! If you have never seen a halftone film-positive before your first print job you will probably think that what your non-postscript printer is printing is correct...I assure you it is not! I know this can be very confusing but one easy way to tell is that you will see what appears to be faint little X’s that run through-out your halftone...this is not good...you need a post-script driver for your printer. Of course this is just my own experience! OK, let’s move on...material for your film positive. You again have several choices. However, I use regular old clear transparencies. (for Laser printers) Try several different types if you want to experiment! What you will notice is a bleed from the black (kind of looks like a hallow around the printed area) this is not good. At first you might think it’s your printer, it is not (in most cases) change to a different transparency, until you find the one that gives you the sharpest image. Make sure that your printer is set at it’s highest density and it’s highest resolution. (note: two different things) check your printer manual for the correct procedure. Also, be sure to check those settings before you print each film positive. They sometimes have a tendency to revert back to the default settings.
Now, we’re ready to print...
End of part one!
(to be continued)
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