Risks of cropping/rotating

S

Set_Nights

Suspended / Banned
Messages
387
Edit My Images
Yes
I crop and rotate a lot of my images when PPing without really understanding much (or anything at all really!) about how the images work... i.e. about how what comes out of the camera relates to the sensor size or how using different image sizes within the camera can make a difference in relation to number of pixels?! I don't actually know what I'm saying ^ but I have a rough idea that it all fits together somehow :p.

BASICALLY... what I am asking is does it matter? Should I be thinking about these things when taking a photo or is it all just kind of useless beyond a geeky interest? Does cropping or rotating run the risk of reducing image quality at a noticeable level?
 
It depends how much you crop but yes every time you crop you are throwing away pixels and the fewer you are left with the more you limit the quality of the image. It is always better to get the right crop in camera if you can although sometimes when you think you have it right you realise afterwards it looks better cropped differently.

Simply rotating an image won't reduce size or quality.
 
Cropping just removes some of the image (pixels) but what's left is unchanged so there's no loss of quality. In a sense it amounts to shooting with a lower megapixel camera but wouldn't be a concern unless you were cropping heavily (eg most of image). Potentially reduces the size you could print the image at without a perceived reduction in quality.

Rotating on the other hand could theoretically reduce image quality. As the pixels (dots that make up the image) are laid out in a grid, if on rotation a pixel didn't fit into a square in that grid then the software must interpolate (make up essentially) what the pixel in that box should look like based on the surrounding pixels.

In reality, with such high resolutions these days any possible effect from this would be all but imperceptible. The aesthetics and quality of the image is affected much more by an appropriate crop and orientation (eg straight horizon) than any theoretical/insignificant reduction in quality.

Short answer, don't worry about it! :)
 
Last edited:
AndyB said:
It depends how much you crop but yes every time you crop you are throwing away pixels and the fewer you are left with the more you limit the quality of the image. It is always better to get the right crop in camera if you can although sometimes when you think you have it right you realise afterwards it looks better cropped differently.
Click to expand...

So how do you crop in camera? I mean the obvious is just deciding on the composition and how it should look when you shoot but why do camera have different inbuilt output sizes (if that makes sense :p)? For my 450D its not too drastic: 3 sizes ((L) 4272x2848, (M) 3088x2056, (S) 2256x1504). Why would you ever pick smaller sizes? Just to save space? I guess I'm asking more about the P&S I'm thinking of buying. It has output image sizes of:

4:3 - (L & RAW) 3648 x 2736, (M1) 2816 x 2112, (M2) 1600 x 1200, (S) 640 x 480, Resize in playback (M2, S, 320 x 240)
16:9 - (L) 3648 x 2048, (M1) 2816 x 1584, (M2) 1920 x 1080, (S) 640 x 360
3:2 - (L)3648 x 2432, (M1) 2816 x 1880, (M2) 1600 x 1064, (S) 640 x 424
1:1 - (L) 2736 x 2736, (M1) 2112 x 2112, (M2) 1200 x 1200, (S) 480 x 480
4:5 - (L) 2192 x 2736, (M1) 1696 x 2112, (M2) 960 x 1200, (S) 384 x 480

Why so many :eek:? Does it make a difference?

dfawkes said:
Rotating on the other hand could theoretically reduce image quality. As the pixels (dots that make up the image) are laid out in a grid, if on rotation a pixel didn't fit into a square in that grid then the software must interpolate (make up essentially) what the pixel in that box should look like based on the surrounding pixels.

...

Short answer, don't worry about it! :)
Click to expand...

This is what I thought was the case but it's good to know that it doesn't really make enough difference to worry about :D.
 
Cropping in-camera just means composing correctly.

Rotating in some software does reduce the quality of the image but I believe that use of higher end software like Photoshop (and even elements) will not reduce quality
 
Set_Nights said:
So how do you crop in camera?
Click to expand...
It's not about changing the size of the recorded image in the camera but framing the image you want as you want it using the camera. Eg if you don't want that tree in the picture, then adjust your position/zoom/etc using the camera so it's not in the captured image so you don't have to crop it out later. Similarly it's better to have a level camera for a level horizon so you don't have to fix the slope using software.

Both are easier said than done (or remembered!) hence why the tools exist to sort them. But AndyB's quite right for absolute optimal image quality you would get your framing and rotation correct before pressing the shutter release.
 
EOS_JD said:
Cropping in-camera just means composing correctly.

Rotating in some software does reduce the quality of the image but I believe that use of higher end software like Photoshop (and even elements) will not reduce quality
Click to expand...

I use Lightroom 3, I assume its decent enough?
 
I'd be surprised if even a critical eye would note much in the way of degradation. I'd suggest you're fine and can quite happily rotate away in LR3 (I know I do!).
 
dfawkes said:
I'd be surprised if even a critical eye would note much in the way of degradation. I'd suggest you're fine and can quite happily rotate away in LR3 (I know I do!).
Click to expand...

Woop woop :).

Any comments on why cameras have so many size presets? I assume its best to shoot with the largest size possible assuming that the crop is right?
 
Because they can :)

It's a bit silly the range of options they give really. However for whatever reason some people may not need higher resolutions - eg if you're only shooting something for Facebook, etc then a low res is arguably fine and saves you storage space on memory card (more shots) and hard drive.

My advice would be to always shoot the largest unless you have a good reason not to.

With respect to 'crop' (the framing of the image, what it looks like in the viewfinder/LCD) it's unaffected by the image size. The image size just determines how many pixels are used to record the image. Pretty much the same as if you had a larger image and resized it to be smaller, it looks the same but has fewer pixels (data) making it up. Apologies if that's not what you meant!
 
Last edited:
dfawkes said:
Cropping just removes some of the image (pixels) but what's left is unchanged so there's no loss of quality. In a sense it amounts to shooting with a lower megapixel camera but wouldn't be a concern unless you were cropping heavily (eg most of image). Potentially reduces the size you could print the image at without a perceived reduction in quality.
Click to expand...

That was what I meant by reducing quality - in terms of the size at which the image can be reproduced, by cropping off some of the image you can no longer print to the maximum potential quality offered by the camera.
 
Of course sometimes you may want to crop to achieve a different format - e.g. you might want the final image to be square, or letterbox. It's best to have this in mind when you shoot, so that you don't have to crop more than necessary, though.
 
Rotating on the added duke could apparently abate angel quality. As the pixels are laid out in a grid, if on circling a pixel didn't fit into a aboveboard in that filigree again the software have to admit what the pixel in that box should attending like based on the surrounding pixels.
 
As for why manufacturers offer multiple image sizes as an option on their cameras...it's an inexpensive option for them to supply and it helps meet the needs of a diverse clientele. Not everyone has the latest, fastest computer, and they don't want to try to manipulate huge files for everythihg they shoot.

A realtor, for example, for the most part really doesn't need a 12 mp file, and can easily get by on a 5 mp file.

Also...smaller files take less space not only in the computer and on the card, but also in the buffer, so someone wanting to take a large string of photos, again, may be more concerned about quantity than quality. A photojournalist holding his/her camera above the crowd trying to get that one great shot of a key person about three feet away, is likely taking 8-9 shots/second for several seconds in a row.

And there are many, many more examples of people who need less than the maximum quality a camera can produce for at least some of their photography.
 
paulwalker said:
Rotating on the added duke could apparently abate angel quality. As the pixels are laid out in a grid, if on circling a pixel didn't fit into a aboveboard in that filigree again the software have to admit what the pixel in that box should attending like based on the surrounding pixels.
Click to expand...

Sure your name isn't Stanley Unwin? :shrug:
 
You must log in or register to reply here.
Back
Top