Hi all,

I have some question about scanning on flatbed scanner, i am trying to scan some of my sketch on flatbed scanner.

I saw the highest resolution of my flatbed scanner is 1200dpi, so i scanned with this option and i got a 132mb TIFF, 14000x9900 pixels.

when i tried to re-size it in photoshop, i saw the resolution is 1200pixel per inch.

I am not sure what i do is correct, but i think it is usually 300 pixel per inch for printing, so i set it to 300 pixel/inch, the size of TIFF change to 3500x2500 pixels, and the files size is from 132MB to 8.3MB.

i am not sure what i am doing, but what setting i should do to preserve the quality? i thought that changing pixels/inch is only a way of calculation and not affecting the image quality, but why such a reduce in file size?

anyone can advise what i should do?

When you open the Image Size dialogue box, uncheck the Resample Image box. Then make the Resolution change.  That's the difference between Resizing and Resampling.

Here's the tutorial:
http://www.photoshopessentials.com/essentials/resizing-vs-resampling2.php

Hi mtkang
The actual pixel dimensions of the image dictate the "quality" (the number of little pixel squares that make up the image). The ppi (or dpi for printing) tells it how to display or print.
If want to just change how it displays or prints by default but keep the image fundamentally the same then you can Open the the Image Size dialogue box, put in the desired ppi then put in the original dimensions in the hight/width boxes, which will have changed with the ppi (do this without closing and reopening the box, or you will downsize then upsize with horrible results).
You will know if you do it right because PS wont have to make any calculations, the change will happen instantly and the image should look no different.

i am not printing it at this moment, my purpose is to prepare a file to sell as a stock like in alamy.

i scanned as 1200 dpi, and this is the file i got
132mb TIFF, 14000x9900 pixels

i want to convert to jpg, i click photo 'image size' and there are pixels dimension and document size, i saw the document size is showed as 1200 pixels/inch

i am not sure what the setting i should get my jpg, do i have to change it to 300 pixels/ inch in the 'document size' setting? and i notice if i change to 300 pixels/inch the pixels dimension change to smaller sizes.

should i just ignore the pixels/inch and only adjust the pixels size to get a jpg size i need?

when i set 300dpi, the whole images pixel size is becoming 3000x2000 something, does it mean I 'shrink' the image and didn't preserve the original quality?

Set the document size to 300 dpi. That should do it.

i am not printing it at this moment, my purpose is to prepare a file to sell as a stock like in alamy.

i scanned as 1200 dpi, and this is the file i got
132mb TIFF, 14000x9900 pixels

i want to convert to jpg, i click photo 'image size' and there are pixels dimension and document size, i saw the document size is showed as 1200 pixels/inch

i am not sure what the setting i should get my jpg, do i have to change it to 300 pixels/ inch in the 'document size' setting? and i notice if i change to 300 pixels/inch the pixels dimension change to smaller sizes.

should i just ignore the pixels/inch and only adjust the pixels size to get a jpg size i need?

Okay, you have scanned a file at 14000 x 9900 pixels, this is what is important. For now, forget about file format, size and DPI. You have a bitmap image that is 14000 x 9900 pixels, you have created an image that is 138 mega-pixels, a huge file. What size file do you want to create?

mtkang,

What are you scanning at 1200 dpi?  A printed image?  I remember HP saying it's useless to scan at above 600dpi because this is the maximum printing resolution for photo prints.  Going beyond that is like using digital zoom.  And even 600 dpi may be a higher resolution than the original print had.

Most sites don't require a specific dpi, but there is one (hmm, which one?) that requires 300dpi. But as Rimglow explained, you have to uncheck the "Resample Image" box, so you change dpi without changing image size in pixels.

Quote from: mtkang on October 22, 2010, 05:15

i am not printing it at this moment, my purpose is to prepare a file to sell as a stock like in alamy.

i scanned as 1200 dpi, and this is the file i got
132mb TIFF, 14000x9900 pixels

i want to convert to jpg, i click photo 'image size' and there are pixels dimension and document size, i saw the document size is showed as 1200 pixels/inch

i am not sure what the setting i should get my jpg, do i have to change it to 300 pixels/ inch in the 'document size' setting? and i notice if i change to 300 pixels/inch the pixels dimension change to smaller sizes.

should i just ignore the pixels/inch and only adjust the pixels size to get a jpg size i need?

Okay, you have scanned a file at 14000 x 9900 pixels, this is what is important. For now, forget about file format, size and DPI. You have a bitmap image that is 14000 x 9900 pixels, you have created an image that is 138 mega-pixels, a huge file. What size file do you want to create?

hi massman, i want a jpg format that's less than uncompressed size 100mb.

i also want to understand what is the way i should do in order not to change the image quality. Just like blufish said it, change to 300dpi? the pixels size will change in this case, any quality change of image?

Open your image and make your 'image size' dialog box the same as this one, start with the resolution and then the pixel dimensions. This screen grab is based on your image size of 14000 x 9900 down-sampled to create an uncompressed file of less than 100MB, you will suffer no loss of image quality. Save as jpeg. This will give you the solution you are after.

ok thanks everyone for explanations..

I read something like 'resample' is like changing the pixels..

I by resample is 'ticked', when i change the resolution of document from 1200 to 300 pixels/inch the pixel dimension shrinks.

I tried to unclick the 'resample' and pixels/inch is not affecting the pixel dimension.

For my understanding the pixels/inch and document document size is just a figure that should not change the pixel information, and the end user can always change it.

I just tried to change the pixel dimension as what massman had suggested 7000x4950 to keep it under 100mb and unclicked resample and change the resolution information.