Dead Fish

Scanning 35mm film

About why to design before implementing

Yesterday I gave a shot at trying to scan some of the 35mm negatives of my old Black&White photos using a 1200 DPI flat-bed scanner. It failed misserably:

• The scan showed severe Moiré and other kinds of noise in the pictures.
• The sizes of the TIFF files were enormous.
• At 1200 DPI the flat-bed scanner picked up dust and stains from the glass.

Although it was just an experiment, the terrible results led me to do some research. Unless otherwise stated, the following numbers come from the article about Digital Photography at Wikipedia.

Resoluiton of 35mm film

The Wikipedia article says that a DSLR resoluiton of 6 to 14 megapixels aproximates that of 35mm film, and that one of 16 megapixels exceeds it, so lets asume that the resolution of 35mm film is 14 megapixels.

To compare with the scanner resolution we need to translate that to DPI. Megapixels are calculated as the product of the vertical and horizontal resolutions:

M=x*y

The Aspect Ratio of 35mm and DSLRs is known to be (3:2), or 1.5. Thus:

x=1.5*y
y=x/1.5

and

M=x*(x/1.5)
M=x^2/1.5
x=sqrt(1.5*M)

So, at 14 (actually 14.7) megapixels, the number of horizontal pixels in 35mm film is about 4693. If we divide that by 1.38" (35mm translated to inches), we obtain 3405 DPI for 35mm film.

Required resolution

With that result it is not surprising why scanning 35mm with a 1200 DPI scanner produces terrible results: 65% of the information in the negative is not captured. Even more, according to Information Theory, the sampling density must be the double of the information density, which means that the scanner should have a resolution of at least 6810 DPI to sample a 35mm negative without bias.

Guess what? The resoluiton of specialized 35mm film scanners is of above 7000 DPI…

RAW Mode

The less, the better

According to Wikipedia:

A raw image file contains minimally processed data from the image sensor of a digital camera or image scanner. Raw files are so named because they are not yet processed and ready to use by a bitmap graphics editor, printed, or displayed by a typical web browser. The image must be processed and converted to an RGB format such as TIFF^? or JPEG^? before it can be manipulated.

Actually, today many image browsers and editors are able to process the RAW image formats of leading camera vendors.

• Microsoft's "RAW Image Thumbnailer and Viewer for Windows XP" allows you to view thumbnails and use the Picture Viewer application over RAW files.
• Google's Picasa now supports various RAW image formats, from indexing to editing.
• Adobe's Lightroom project will provide professional-quality cataloguing and editing for images in RAW format.
• The latest versions of the software that comes bundled with digital cameras allows for basic editing of RAW images. Such is the case with my camera^?.

As I see it, the digital RAW is the equivalent of the film negative, and there's no way to go if you're serious about your photography than to shoot and transfer your pictures in RAW format.

For a nice explanation of the whys and the trade-offs, read the Understanding Raw Files article by photographer Michael Reichmann.

Black and White

The lost beauty

My first serious attempts at good fotography where with black and white. I cannot tell now if it was the artistic nature of B&W of photography or it's easiness over budget which dominated, but I'm sure both were involved.

Today, I'm getting my self ready to try B&W again using a My Camera^?, so I've been doing a bit of study.

If you like B&W photograply, you should stop by photographer Keith Cooper's site and read some of his excellent articles about digital B&W photography. They are all hyperlinked, and almost any article is a good starting point.

Dicho eso, Marcelo dice:

Lamentablemente, las sutilezas que hacen el B&W ser tan bello, se perderan con el pasar del tiempo, como se perdio la belleza del daguerrotipo, como se perdio lo rico del los bajas frecuencias de los discos de vinyl, lo agradable de los instrumentos barrocos. Asi es la vida.

Yo no he experimentado mucho con blanco y negro en photoshop, pero he jugado un poco con lo de los filtros. Pero me refiero a filtros de colores (como el anarajado) que se ponen en el lente de la camara, para resaltar los tonos grises… bueno me puse a jugar en photoshop poniendole un layer anaranjado casi transparente, encima de una foto a color, y luego la converti a grayscale, y le salieron unos tonos grises bellos.

Como en muchas otras expresiones de arte, no hay reglas precisas de como hacer las cosas. Depende del artista, de como usa las herramientas que tiene disponibles.