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If we advertised this:

Mica - Grayscale

And sent you this:

Mica - Bitmap

I bet you would send it back.

The following is taken from our 'Bronze' page.

Many manufacturers we've reviewed do etch bronze and other metals. Plaques&Letters distributes products by Matthews Bronze and Gemini. Following are two quoted paragraphs from their Web site.

Gemini Signs & Letters

“The etching process allows you to replicate your photograph, line drawing or complex artwork. This method utilizes a halftone dot pattern made from a 50-line screen. Halftone portraits resemble newspaper photographs, and have visible dot patterns. The recessed dots are black infilled to contrast with the satin finished metal background.”

Matthews Bronze

"Cast Bronze Plaque Etched Portraits Appliqués:

This process utilizes a halftone dot pattern acid-etched on .100" thick bronze plate. The etched, recessed dots are infilled with black to contrast with the satin-finished background. The best photographs for etched portraits have high contrast tones with bright white areas, dense black areas, and minimal gray tones.

Gemini says they use a 50 line screen, about what they use on silk screen T-shirts. Newspapers use an 85 line screen. Magazines use 133- 150 line screens. There's a big difference, especially when we talk about image resolution. On their Web site Matthews recommends 72 - 300 dpi images. Keep the two figures (in yellow) in mind as you read on.

I have prepared the following so you can better understand how we differ and why we call our imaging 'High Resolution' no matter what the competition calls theirs. There is a difference!

For this demonstration I used three grayscale (8 bit) scans, one @ 72 dpi (dots per inch), one @ 300 dpi, and one @ 1,200 dpi - the resolution we use. I then converted these to black & white bitmap (1 bit) images in Photoshop using one of three line screens - 50 lpi (lines per inch), 85 lpi, and 133 lpi - the line screen we use. I used the image below for this demonstration. The red box around the eye was the sampling area. I had to use a small area because putting the large images on the site would be impractical. The small area serves the purpose.

As I mentioned, I did the line screens in photoshop. During production we use an imagesetter to produce a halftone screen at 2,450 dpi. The imagesetter is superior to using Photoshop for that procedure. But these Photoshop screens will show you how dpi and lpi relate to final halftone resolution. defines a halftone as:

"A picture in which the gradations of light are obtained by the relative darkness and density of tiny dots produced by photographing the subject through a fine screen."

The imagesetter takes the place of the photographic equipment and the screen. Photoshop is a less expensive substitute. Halftones are simply made up of solid black dots. A grayscale image can reproduce 256 shades of gray, the most the human eye can distinguish. So to get the maximum shades of gray using a halftone one must use a high resolution imagesetter. The formula for obtaining shades of gray is: number of gray levels = (printer output resolution / line screen) squared + 1. If you try to print a 133-1ine screen on a 1,200 dpi imagesetter you would only be able to achieve 82 shades of gray (1,200/133 = 9.02. 9.02 x 9.02 = 81.36 + 1= 82.36). By using an imagesetter printing film @ 2,450 dpi we can achieve the maximum 256 shades of gray in our images. By using a 1,200 dpi image (termed Archival Resolution - a minimum 1,000 dpi) to begin with we have more information to feed the imagesetter.

Mica - Grayscale

Click any of the nine images below for enlargements.

Eye Sample
72dpi - 50lpi
Eye Sample
72dpi - 85 lpi
Eye Sample
72dpi - 133 lpi
Above you see the section of the snow leopard's right eye (red square). They are identical. Why is that? At a low resolution, like 72 dpi, there is not enough information in the grayscale image for the program to interpolate a round dot, so it uses what information it has to produce a screen. For a detailed definition of a grayscale image you can click here.

Eye Sample
300dpi - 50lpi
Eye Sample
300dpi - 85lpi
Eye Sample
300dpi - 133lpi
In this series of images a 300 dpi photo was used. The program can do better at determining a round dot in the first image, but at 85 lpi it breaks down. You can see quite a difference between the 50 lpi screen and the 85 lpi screen - more image detail. There is virtually no difference between the 85 lpi and the 133 lpi screens. There's not enough information in the image.

Eye Sample
1200dpi - 50lpi
Eye Sample
1200dpi - 85lpi
Eye Sample
1200dpi - 133lpi
You can see a big difference in the 1,200 dpi image. There is a very distinct difference in all three screens. The image resolution in the third frame is superior. That's why we use it. That's high resolution. Some of the dots in the third image are 11 thousandths of an inch. We've actually imaged a dot of 1/10,000".

Dot Detail Willie Reduction

To give you a better idea of how an imagesetter differs from Photoshop I scanned an actual piece of film - left picture above. The film was set at 133 lpi using a 1,200 dpi image. Click on the image to see how the dots look. The picture of Willie, on the right, is a reduction of that larger image.

Product Dispaly & Web Images

Now I want to address the issue of reproducing halftone images on the Web as it pertains to product display. The rendition of products that feature halftone images can be deceptive. We fall into this predicament ourselves. Fortunately our final output is represented quite faithfully through the images you see on htis site.

When I visited a competitor's site I saw a small picture of an etched portrait on bronze. I discuss these on our 'Bronze' page. That small picture appears photo realistic even though I know the company is using a 50 line screen and at most a 300 dpi image. They did not offer a high resolution download or a large photo link so one could more closely examine the detail. Although I've found that a larger photo does not necessarily give you the information you seek. Why do these pictures look like photos? The answer lies in the digital reproduction and the reduction.

When we reproduce products for presentation on the Web or in catalogs we either take photographs or perform scans. The common denominator for all of us is that we cannot accurately reproduce an image that is made using a black and white halftone. Those images have 1 bit per pixel information. If we take a digital photo (RGB) the pixel information is 24 bit. If we scan a photo in grayscale the pixel information will be 8 bit. If you try to scan the image as a black & white bit map the result is not representative, to say the least. Below is a bit map scan of a small section of our soldier tribute. What a mess. That does not represent the image.

Bitmap Scan

If we take a grayscale scan and try to convert it to a bit map you get something like this:

Bitmap Conversion

I want to show you how the additional information in a grayscale can affect the resampling of an image. The image below is 72 dpi that's been screened at 50 lpi creating a halftone (bit map). Even though it looks like there are gray areas in the image, it's all black dots. (See the 72dpi - 50lpi cut out in the group of nine images at the start of this presentation.)

Mica - Bitmap

If I take this same image and resample it down to a smaller version (42% of the original - dpi remained the same) this is the result.

Bitmap - Reduction

The program attempts to interpolate the limited information available when forming a new image. Below is a 200% resample of the eye area. When performing the enlargement the program added small black dots. Resampling upward is not recommended in most cases.

Eye Detail

I took the same bit map image of the snow leopard, 3rd above, and converted it to grayscale. The resulting 8 bit image looked exactly the same as the 1 bit image. However, when I reduced or enlarged it the program used all that additional information to render a different result. Below is the grayscale image reduced to 42% of the original - dpi remained the same.

Grayscale Reduction

Quite a dramatic difference, wouldn't you say? Those nine small images of the eye area at the beginning of the presentation are all grayscale reductions of the larger .gif images. The .gif format can render bit map images. The .jpg format cannot. When I reduced the large 1 bit images to make smaller representations the results were unsuitable - carved out dots all over the place. So, for better thumbnails I had to convert to grayscale.

When we take a higher resolution 8 bit or 24 bit digital image, reduce the dpi and dimensions, and use it for a Web presentation we get the effect represented above. The higher resolution image that revealed the dot pattern, even though its been endowed with more pixel information than the halftone, looks like a continuous tone photo when reduced. Refer to the two samples of Willie. The greater the reduction the tighter the image gets. (The reason we scan at higher resolutions, or use a descreening option, is to remove the moiré patterns you get when scanning halftone images. Pronounced "mor-ray" and spelled "moiré." In computer graphics, a visible distortion. It results from a variety of conditions; for example, when scanning halftones at a resolution not consistent with the eventual printed resolution or when superimposing curved patterns on one another.)

So I now know the small thumbnail image of that etched bronze plaque produced using a 50 lpi screen I saw on the Web would not be representative if I could see the actual product.

The option I chose as most enlightening - one where you can see a representation of the image's halftone - was to do a high resolution scan (1200 dpi) of the film used in the production of a tribute. Even though the scan produces a grayscale representation, the high resolution reveals the dot pattern quite nicely. Ask other manufacturers to provide a similar scan (1200 dpi) of one of their films so you can compare apples to apples.

The Gallery images do represent our tributes very well. They actually look like our scans. Our Archival Resolution images coupled with a 133 line screen yields photo realism on our metal tributes and jewelry that others have not achieved. Immortal Memories™ tributes will faithfully represent our loved ones and immortalize your thoughts for ages to come.

Never Forget!

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