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DPI Pixels Printers and Scanners
There are two main areas that we must consider when you are using BlackMagic to color your photos or when you are using VideoSnaps to extract images from film. These are scanning and printing.
Luckily VIDEOSNAPS users do not have to worry about the scanning side of things as the software will automatically load up a movie from your hard drive ( getting a movie onto your hard drive will be the subject of a future tutorial)
However at the end of the day both pieces of software need a means by which you can show off your work, sure you can keep the images on your hard drive or post to the web, but at the end of the day I am sure many of you will want to see have copies of the colorized or extracted images.
Most of us know HOW to print and hopefully most of know HOW to scan, fear not if you are a real newcomer to these topics as we will go into them later. However there are some concepts that even the most seasoned digital artist find confusing and these are DPI, Pixels and Resolution - sometimes I think quantum physics is easier to understand that these three !!
Pixels
So what are Pixels ? Baby Pixies ?. Well if you were to look very closely at a television screen you will see that it is made up of what appear to be cell like structures each capable of being in either one of three states of color, Red, Blue or Green. From a distance these “cells” blur together to produce the illusion of a smooth colored image.
The same is true in print, look closely at a color image on a magazine and you will see that the image is made up of individual colored dots that from a distance merge to give the illusion of an image.
These concepts were the core of the Pointillist technique of the Neoimpressionist painters and if you ever get the chance to study Seurats’ work you will see the technique in all it’s glory
In digital imaging terms the “cells” are called pixels and a typical digital image is made up of millions of these pixels and each pixel is given a Red, Blue and Green value, known as RGB, the levels of each chanle decide on the final mix and the color outcome. Typically images are stored as either 8 bit 16 bit 24 bit or 32 bit images. Most home users should be content with 24 bit images and these consist- of 8 bits red 8 bits blue and 8 bits green ( a bit being the smallest unit in a computer storage- compare to bytes which are 8 bits and megabytes etc) Obviously the more bits an image has the more color information that it can store..you see its all down to the binary system of mathematics. If you look at any color picker on your computer you will see that the Red Blue and Green components can be anywhere from 0 to 255, this is the limitation of 8 bits..you see I told you particle physics was easier !!
DPI
DPI stands for dots per inch it is commonly used when referring to printers, scanners also use the term DPI and also a similar term SPI (samples per inch) there is also PPI (Pixels per inch) but as we are all getting a headache now we will stick with the more common DPI
So what exactly are DPI ? DPI when used with a scanner means that a scanner will create so many dots or pixels for every inch of the image scanned. So lets say we scan a 8x10 photograph at 300 DPI we would get a digital image that is 2400 pixels wide and 3000 pixels in height. 8 x 300 = 2400 and 10 x 300 = 3000.
This gives us an image with the resolution of 2400z3000, the higher the resolution of an image the more detail it has and the larger the file size.
What does that all mean in MegaPixels ? well we simply multiply the height and width to get that, so the image would be 2400 x 3000 = 7200000 or 7.2 MegaPixels
In general when scanning photos for later enhancement I would suggest scanning at 300 DPI, this should capture more than enough detail to work with, if you are going to be printing out at greater than 8 x 10 then perhaps you could scan in at 600 DPI. If however you are trying to enlarge the image say you scan in at 8 x 10 but want to print at 16 x 20 then you will probably loose some detail, in which case it may help to scan in at even higher DPI if your scanner allows
Scanning and Printing With BlackMagic
Scanning
To scan images into BlackMagic you need to have a TWAIN compatible scanner connected. Most scanners today are plug and play and if you have any issues then please refer to the documentation that comes with your scanner product.
Once BlackMagic is running simply click on the SCAN button. You can choose to scan a color image as color if you wanted to enhance it or maybe just scan it in as black and white to do a complete color “overhaul”. From the information above you can decide on the DPI resolution you want to use depending on the limits available to your scanner.
Printing
Most of the settings in the print options are self explanatory and well covered in the help manual however the options for print resolution are relevant to our discussion and I will quote from the manual:
Screen to Print Resolution Translation: The screen resolution (number of pixels in an inch of space) is mostly quite different that that of a typical graphics printer. as a result, when you print an image, it may not appear on paper to be of the size that you expected. Having this Check-box in the "Checked" state tells BlackMagic to try and translate between the two resolutions, so that the printed output size resembles more to what you see on the screen. For very high resolution image printing on high resolution professional photo printers, this may sometimes be un-desirable; in that case "Un-check" this box. On the other hand, not having this option selected for printing on an average home printer may provide only a very small size print out. Note: this setting does not have any effect when the "Scale to Fit Page" option is selected
Here endeth the first lesson..in later tutorials i will go into more detail about DPI and resolution so you can get the best end results when you color your black and white photographs
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