Monthly Archives: August 2008
Scanning At The Right Resolution
Most commercial printers print at 300 dpi which is suitable for 150 to 175 lpi. So in order to get a photo printed at 300 dpi the final resolution of the photo after resizing should not be less than 300 dpi. When you resize a photo after scanning the dpi increases or decreases depending on whether the photo is scaled down or scaled up. That is unless you re-sample the photos in Photoshop by clicking the re-sample button. Re-sampling up is not advised unless absolutely necessary and even then the photos should not be re-sampled up more than 10 percent otherwise the quality will deteriorate. Re-sampling down is alright but should be done after the image has been finally edited.
Now if suppose a 7×5 inches photo is to printed at 300 dpi then we have to scan the photo at 300 pixels per inch. However if the photo is to be enlarged to 14 x 10 inches then 300 pixels would not be sufficient as when the size is increased the dpi will go down, in this case, to 150 dpi. So in order to maintain the same dpi the pixels have to be increased. A 14 x 10 inches photo at 300 dpi requires 4200 x 3000 pixels (14×300 = 4200, 10 x 300 = 3000). To get this pixels the 7 x 5 inches photo has to be scanned at 600 pixels per inch ( 4200/7 = 600, 3000/5 = 600).
As a rule when the photo is going to be resized at twice the length and twice the breadth the pixels have to be doubled. So scanning resolution of 300 ppi becomes 600 ppi when the length and breadth of the scanned picture are to be doubled.
Common Book Sizes
Some of the common sizes in which books are published are :
1) 8.5 x 11 inches – 1/4 single demy size used mainly for magazines and souvenirs.
2) 5.5 x 8.5 inches – 1/8 single demy size used for paper backs and other books.
3) 7.25 x 9.5 inches – 1/4 single crown size used for notebooks and magazines
4) 4.75 x 7.25 inches – 1/8 single crown size used occassionaly
5) 4.25 x 5.5 inches – 1/16 single demy size used for very small booklets.
Other sizes
1) 8.5 x 13.5 inches – 1/4 DFC size. used for registers and small threefold brochures.
2) 6.75 x 8.5 inches – 1/8 DFC size used for notebooks
3) 7 x 5 inches – 1/16 of a 22 x 28 inches Board used for invitation cards.
4) 7 x 4 inches – 1/18 of a 22 x 28 inches Board used for invitation cards.
5) 6 x 4 inches – 1/20 of a 22 x 28 inches Board used for invitation cards.
Macro Print Offset Machines
Macro is another mini offset printing machine company based in Coimbatore, India. The first machine that we bought five years back was from them – the 15×20 Macro Deluxe model. We are still using it. During the course of these five years we had to change some parts such as dampening roller and the plate clamp. We have found the machine to be quite sturdy and reliable. It has 11 inking rollers and two form rollers. Some four color jobs can still be run on it and there is no registration problem. The cost of the machine comes under Rs. 500,000/- It does not need a stabilizer like some other machines. and there is no problem running it on generator power.
Some of the draw backs of the machine is that it is a two cylinder machine and scum is a constant problem. One person has to sit on the back where the plate is and keep on wiping the plate from time to time. Another problem with the deluxe model is that it has a motorized feeder table lifting. The problem with this is that the machine operator has to manually press the table lifting button from time to time as the auto lifting function is very difficult to adjust without stopping the machine. All this hampers the production and thus the day’s total number of impressions may come down.
It seems that Macro is not too keen on improving their offset section. Instead it has gone for manufacturing of thermal lamination machines which has become very successful and they received good responses for this even during Drupa 2008.
Visit their website at www.macroprintindia.com