Hi
For the first time I got my negatives scanned. I had no idea how to go about it and lab that does it did at 72dpi. I had told them I want to create photographs of dimension of 8x10 size but when I opened scanned images, this is what I observed.
Size of image 1544 x 1024 pixel at 72 dpi , when I try to resize it to 8x 10 using dpchallenge’s tutorial I get following values 8 x 12.063 @ 128 dpi, hence now I have to interpolate it to 300 dpi and also say crop 12.063 to 10 .
My point is that when I get next negatives scanned at what dpi should I get them scanned so as to avoid interpolation altogether
Secondly in some rare cases where I have to crop a lot due to poor composition or the subject I need enlarge is small than what would be ideally setting to get it scanned at
As these snaps have been clicked a my cousin who portraits using auto focus camera and as result cause too much useless background , simply speaking awful composition and I simply cannot make enlargement with that composition
Sounds like they are used to scanning for folks who only want to print 4x6. They should re-do it for you. If the image came out at 1544px, they originally scanned at about 1100dpi. That's too low to capture all the detail in a 35mm negative. For your intended print size, they should scan at a minimum of 2400dpi. They probably have the capability to scan at up to 4000dpi.
Also, many places which scan for others charge by the ending file size.
For a 35mm neg you should end up with about 4096 x 2732 pixels or about a 32MB file -- that yields an image about 9 x 13.5 at 300 dpi.
As kirbic says, most transparency scanners (especially pro versions in a service bureau setting) should have an optical resolution of about 4000, and could give you a file about 50% bigger than that, if you want to pay for it.
If you are going to interpolate, you will have to have dpi loss.. 150 dpi for the maximum printable size is generally accepted. I woudn't try to upscale from 128-300dpi that will give some bad results. I'd try to get a lab that will scan at 300 dpi or higher so that you can down size instead of upsize to regain clarity instead of lose it.
I think the moral of the story is get a film scanner and do it yourself, particularly if you plan to scan a lot of negatives and slides.
The feedback I get from most people who have anything done digitally by commercial photo labs is of general disappointment. Of course this is nothing new, most commercial labs never did a very good job processing and printing film either.
