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emailed photos
Hope someone can help.
What do you do to get good quality prints from emailed photos?
James
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4 Replies
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Hi James
Emailed photos tend to be low resolution 72 dpi and jpg format. Not good for printing. If you can’t get a bigger file emailed to you, try and enlarge them in photoshop and use a blurring/smoothing filter on them.
150 dpi is minimum for printing so a 6 x 4 print needs to be 900 x 600 pixels, still not great, 300 dpi is better.
If you haven’t got photoshop you could email me the small file of a sample and I will see what I can do. If the small photo is good quality, not too compressed, it could work.David
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Thanks for that David will have a go with photoshop.
James -
Hiya
The DPI of the photo is not really relevant , as with women , Size is:)
Essentially a printer cannot map a single pixel to one dot , as it only prints 7 colours , so what it does is maps a single pixel to a cell of dots. This “cell” uses a whole lot of dots overlaid and spaced to fool the eye as to the colour the pixel represents.
Thing is , top quality printers , even at 1440 dpi (thats how many dots it can print per inch not cells) can only manage 125-150 or max 200 cells per inch.(often called LPI)
So essentially you really only need about 120 pixels per inch of printed output to get a really good looking print out of a photo.
The fact that a graphic is emailed has no bearing on the issue.
Lets say you have a graphic thats e-mailed to you that is 720 pixels by 480 pixels. This file will be a 1 meg file (uncompressed – 720x480x3) and most likely a 70-100k jpeg.
You could print this file 6″ x 4″ and have an almost perfect picture , you could most likely scale it by 1.5 and still have a great picture if you are working on a device capable of 120 LPI (lines per inch) and remember a 1440 dpi printer is most likely only capable of 120 lpi (the cells thing)
If you display that picture on a monitor , which is a 72 dpi device , the displayed graphic will be 10″ (720/72) x 6.6″ (480/72) .
But why dont you divided the 720 by 1440 for printing , you might ask?
Well remember that the monitor CAN map one pixel on the screen for one pixel in the graphic , the printer CANT!!!.
So essentially the formula you use is 120-150 pixels per printed inch of graphic , and using that will give you the biggest size you can print to.
This works well for scanning too , essentially the DPI (which is actualy the Pixel per inch) you need to scan at can be worked out like this
Output size/input size x 150(we use 150 to play safe)
IE if you have a 6″ pic and you want to print it 4 ft , the DPI is needs to be scanned at is 48/6×150 which is 1200DPI.
If you dont have enough pixels to print big , you can “interpolate” or resample (guestimate new pixels) the graphic. The best interpolation (or resampling) filter is the lanczos one that comes with the freeware viewer Irfanview.
However this has limited utility as one cant make a silk purse out of a pigs ear. Often adding a touch of Guassian blur at the expense of sharpness smooths things out.
Better printers like variable dot ones and 6 colour ones can actually get close to 250 cells per inch (depending on the media , not all media can even begin to resolve 200 cells an inch , like canvas)
A 300 DPI dye sub printer will outperform ALL those as it CAN map one pixel of the graphic to one printed pixel. -
thanks for that rodney!! 😀
you explained that perfectly, been trying to suss that one out for years!! 😀 😀 😀
Nik
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