Editing cellphone images

[GaryMarsh]

Hello again and a Very Happy New Year to all Cambridge in Colour members!

My first question for 2013 is how best do I edit a cellphone image?

A work colleague has asked me to try and improve a couple of photo's of a dear friend who is unwell which were taken on a Samsung mobile phone, the image properties are as follows: width 3264 pixels height 2448 pixels a resoloution of 72 dpi and a file size of 2.63Mb per image.

From my understanding of digital images 72 dpi is ok for viewing on a monitor but if I was to edit any of these files would I start to lose image quality and see artifacts creeping in because of such a low resolution. What is the best approach? could I go into photoshop and increase the resolution or in technical terms I think this is known as (upsampling) and if so how far could I increase the resolution before adversly affecting quality, also my colleague said that she would like to have them printed out at about 7 x 5 inches. I would be very grateful for any help on this topic.

Regards
Gary

[Manfred M]

Don't worry about the dpi as it has no bearing here; the important statisitic is the 3264 x 2448, i.e. you are working with an 8MP image that have been compressed down to 2.63MB, which is not too bad. These should result in quite acceptable 5 x 7 prints, assume that the images are fairly good in the first place.

Most photo printers are 300 dpi, so 3264/300 = 10.9 inches and 2448/300 = 8.2 inches; so rather than worrying about upsampling, you will actually be downsampling to print at 5" x 7".

[GaryMarsh]

Thank you for your swift reply to my post GrumpyDiver, your input has been very helpful and has helped clear up my mis-understanding of the dpi issue.

Many thanks
Gary

[Manfred M]

The whole ppi issue confuses a lot of people; including me until I did the math. I believe the 72 ppi may original with the NTSC television standard, where displays were 720 x 480. I think there may still be some link with browsers that are designed to handle 72 ppi. With modern LCD monitors this goes right out the window as display formats are much more variable. My 27" monitor has a native resolution 1920 x1200, and the width of the screen is 23" so it is natively 1920 / 23 = 83.5 ppi. If I replaced it with a current model, its native resolution would be 2560 x 1440 or 111 ppi.

Printers are a bit different and I have read some claims that the cleanest images come about if they are fed images that are either at the "natural" setting, or a ratio of that setting. Both Canon and HP run at 300 DPI, while Epson uses 360 DPI. This means building images for HP or Canon printers that are 150 , 300 or 600 dpi. I haven't tried this, so can't comment as to how valid this view is.

[AgfaB2]

Hi Manfred

The whole ppi issue confuses a lot of people; including me until I did the math. I believe the 72 ppi may original with the NTSC television standard, where displays were 720 x 480. I think there may still be some link with browsers that are designed to handle 72 ppi. With modern LCD monitors this goes right out the window as display formats are much more variable. My 27" monitor has a native resolution 1920 x1200, and the width of the screen is 23" so it is natively 1920 / 23 = 83.5 ppi. If I replaced it with a current model, its native resolution would be 2560 x 1440 or 111 ppi.

The best explanation of the ppi/dpi lark I found here:

Say no to 72 dpi.

http://www.scantips.com/no72dpi.html

It's a bit long but written without to much jargon.

You know and I know (now ) but it may help someone who is new to the business.

cheers
Wolf