Beginner resize vs crop

Carpy2001

Carpy2001

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256
Name
Andrew
Edit My Images
Yes
Hi all, when trying to shirink an image file to post on here, should you crop the image or resize it??, it is just that the images I have are all 2.5mb and bigger, a little to large to post on here lol. I have been cropping them down to under 500kb, but I have noticed a lot of the images seem to be grainy.
thanks Andy
 
You want to resize the image.

Cropping an image means that you remove part of the image or to recompose the image. Eg you take a photo of a bird but want the bird to appear larger in the frame then you can crop into the image, removing the unwanted part of the image around the bird. When you crop into an image you are essentially zooming into the image digitally, this will reduce the resolution and while the image is not getting any noisier you are zooming into it which makes it look worse than it was.

Resizing does as it says on the tin. It resizes the image in its entirety.
 
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You can resize a cropped image but it will still be the cropped shape. Cropping simply changes the shape. Resizing changes the pixels somehow, don't ask!
 
Carpy2001 said:
I have been cropping them down to under 500kb, but I have noticed a lot of the images seem to be grainy.
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When you shrink an image in an editor, it deletes adjacent pixels that are the same as their neighbours, so you're taking data out of the file. This is fine if the image is then displayed at the size to which you've shrunk it.

If the image is displayed at a larger size, perhaps because the user has a bigger screen than you, the image will be, as you put it, grainier. It's the same effect as blowing up a small negative too much.
 
Carpy2001 said:
Hi all, when trying to shirink an image file to post on here, should you crop the image or resize it??
Click to expand...
Resize the whole image to (IIRC) 1024 pixels on the long side. Anything larger gets reduced anyway.
 
Cropping will reduce the max print size without losisg quality, as most cameras are 20mp this is not such an issue anymore, and its an optical crop, ie no Changes in the pixels, if an image is resized it alters the pixels count up or down
 
Cropping is changing the picture you have taken.

Resizing is reducing the size of your original picture, but does not change the image.

If you're cropping your pictures a lot to get the image that you originally wanted when you took the picture, then you either need to go closer or get a longer focal length lens.
 
Cropping is like taking a pair of scissors to a print of the image.

Resizing is like squeezing the image onto a smaller piece of paper.

As mentioned above, resize to 1024 pixels on the long side usually works fine for reducing the file size for sharing images on here (and other forums).
 
Ed Sutton said:
Resize the whole image to (IIRC) 1024 pixels on the long side. Anything larger gets reduced anyway.
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If you wish to upload the image to the TP site's server (e.g. because you don't like Flickr or suchlike) you are limited to 850 pixels on the longest side.

Unless something has changed?
 
AndrewFlannigan said:
If you wish to upload the image to the TP site's server (e.g. because you don't like Flickr or suchlike) you are limited to 850 pixels on the longest side.

Unless something has changed?
Click to expand...
I upload pics as attachments at 1200 pixels on the longest side and they work fine, being automatically reduced.
 
Ed Sutton said:
I upload pics as attachments at 1200 pixels on the longest side and they work fine, being automatically reduced.
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For some reason I've long thought the limits were 850 pixels and 500KB.

Just goes to show that I couldn't have been paying attention! :whistle:
 
WELL LOST AGAIN! PIXELS AND kb'S jUST DON'T GET IT. iF i WASN'T SO CHEAP i'D GO BACK TO FILM. ALL i NEEDED TO KNOW THERE WAS GET CLOSER AND WHERE TO TAKE THE FILM TO GET PROCESSED! :) See what I mean. Hit that cap lok key and never noticed it till I got done!
 
Don Fischer said:
WELL LOST AGAIN! PIXELS AND kb'S jUST DON'T GET IT. iF i WASN'T SO CHEAP i'D GO BACK TO FILM. ALL i NEEDED TO KNOW THERE WAS GET CLOSER AND WHERE TO TAKE THE FILM TO GET PROCESSED! :) See what I mean. Hit that cap lok key and never noticed it till I got done!
Click to expand...

It's a bit like driving - feels like there's so much to learn, but after you learn then it becomes instinctive.
 
Don Fischer said:
WELL LOST AGAIN! PIXELS AND kb'S jUST DON'T GET IT.
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I'm not surprised, the word "pixel" gets used in so many different ways.

Originally, it was the name of a single light emiting diode on a display unit. Then the word began to be used as the name for a single light sensitive unit on a digital sensor, After that, it was used to define an element of a grid structure used to store a digitised image...

The relationship between a pixel and a byte is somewhat variable. In the earliest digital image capture and display systems, one pixel's data was stored in one byte of RAM and when written to disk, one byte of a file. Then the data captured by the individual sensors grew, so the information defining a pixel may require several bytes. At the same time, the data required by display units also grew, but in different directions, so 1,000,000 captured pixels will probably use a very different amount of storage than the 1,000,000 pixels to be displayed on your screen and both will be different from the storage for the 1,000,000 pixels on your printed page.

If by this time, you aren't screaming and wrapping your head in your underpants, you clearly haven't been paying attention... :sulk:
 
Depending on what software your usingit's usually worth making a duplicate picture (in photoshop)then cropping that and or resizing. That way you dont affect your original image. If your using Lightroom or a RAW file ignore what I've just said as it's not really loosing anything.
 
swanseamale47 said:
...it's usually worth making a duplicate picture (in photoshop)then cropping that and or resizing.
Click to expand...
Excellent advice,

I always preserve the original file and work on copies.
 
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