How can I crop a photo without losing quality?

Question

Level 1

8 points

How can I crop a photo without losing quality?

I am trying to crop photos and then have them printed to poster size.

The pictures are all 1.2 mb or larger. When I crop them the resulting picture (jpeg) is so small it lacks the resolution for enlarging to poster size.

Is there a way to crop a picture while retaining the quality so it can be enlarged?

Thanks

Macbook Pro, Mac OS X (10.6.4)

Posted on Oct 25, 2010 12:02 PM

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Answer 1

Yer_Man

Level 10

162,308 points

Oct 25, 2010 12:09 PM in response to pd2

No. In fact, I'm not sure that a 1.2MB file will print at Poster size terribly well. But think abiout it. Cropping is removing portions of the data. So the file will be smaller. Then you have the additional level of compression...

What's the Pixel size of these images?

Regards

TD

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Answer 2

pd2 Author

Level 1

8 points

Oct 25, 2010 12:53 PM in response to Yer_Man

TD
Thanks
How do I find out the pixel size?

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Answer 3

Yer_Man

Level 10

162,308 points

Oct 25, 2010 1:06 PM in response to pd2

Click on the wee 'i' lower left and it will show you the Info Pane. Then click on the pic and it will tell you the pixel size.

Regards

TD

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Answer 4

pd2 Author

Level 1

8 points

Oct 25, 2010 1:45 PM in response to Yer_Man

TD
Wow - thanks for your help.
So the little icon "i" is in my lower left picture and when I click on it I go to geographic location.

I think I have drilled down another way to find that the "Dimensions" for the photo are 844 X 1421.

Is this indeed "pixels? And is this large enough for a OK quality poster? If not - what size should I be looking for to get an ok poster size image?
Thanks again

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Answer 5

Yer_Man

Level 10

162,308 points

Oct 25, 2010 2:07 PM in response to pd2

Yes, those are pixels and no you've no hope of getting a poster out of 844 x 1421, I'm afraid.

Here's how it works.

The rule of thumb is that you need 300 dpi (that's "dots - or pixels - per inch") for a high quality print.

Your photo has 1421 pixels on the long side. Use 300 of those into every inch (1421/300) and you'll get a high quality print of about 4 and 1/2 inches on the long side.

So, if you want a poster size of about 40" x 30"... you'll need 12,000 x 9,000. That's about a 10 megapixel camera.

Regards

TD

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Answer 6

Old Toad

Level 10

207,409 points

Oct 25, 2010 2:56 PM in response to pd2

iPhoto has a dpi limit that it uses for alerting users that the resolution of the photo may not be enough for quality prints. The screenshot below are those limits in iPhoto's preference file:

Click to view full size

However, when ordering prints thru Apple that limit seems to have been raised a bit.

The following are the resolution limits and warning that Apple has put on 4 different sized images I prepared for printing to give you an ideal of what to shoot for. Remember, many have used image smaller than what iPhoto warned at and were happy with them. It's all subjective.

Click to view full size

OT

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Answer 7

Old Toad

Level 10

207,409 points

Oct 25, 2010 3:14 PM in response to Old Toad

The following is what Apple recommends as a minimum:

Click to view full size

It's from iPhoto & Aperture: Warning icon when ordering photo products

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