7 Cropping
Most
phones and cameras will have a built in function for cropping. Many
will also have the option to change the aspect ratio of the photos
they take.
The
default aspect ratio for cameras is generally 4:3 but they usually
have options to take pictures in 3:2 and 16:9.
Personally,
I keep it simple and take every picture in 4:3, which uses the most
pixels and gives me the biggest image. True, I crop them all anyway
so I could save myself the work and shoot in 16:9 but I don't. Why?
Because
I don't always crop the top and bottom equally. I photograph moving
things and if they're in the bottom half of the frame, all the
cropping will be at the top. If the camera was set for 16:9, I'd have
a lot more shots I had to throw out because something was flying off
the edge of the frame.
If
we decide on 16:9 in advance, there's nothing we can do about the low
flying duck. Make that choice afterwards and we have a usable image:
Usable but not very good. I'll come back to that in a moment.
Here's
another top tip: Never do anything before the shot that you can do
after. The only part of photography that's time critical is when you
press the button.
The
extra parts of the photo are also handy if you need to airbrush out
something. It's better to copy a detail that's being cropped than it
is to duplicate a detail that's still in the picture. That's another
thing we'll come back to later.
Back
to cropping. Why do it? As I said earlier, I crop to fit the devices
I display my pictures on. The church window was cropped almost
square to make the stonework look like a picture frame but that was
an exception and an aesthetic decision.
Another
reason we might want to crop is to effectively zoom closer to the
subject of the photograph. This is the equivalent of what your phone
does with it's digital zoom function. If, like me, you're going to
display photo's electronically, you really don't need more pixels
than there are on your screen. My phone has about 2 million pixels so
I can crop a lot of my 16 million pixel images and still have a sharp
picture. This is what I actually cropped that duck to.
If
you're going to print your pictures, then you will need to crop them
to fit whatever size paper you're printing on. Cropping isn't
necessarily about size, it's about aspect ratio, but every standard
size of photographic print (and every off-the-shelf frame) has an
aspect ratio.
A
standard small print is 6”x4”,making its aspect ratio 3:2. A
5”x7” print is slightly more square at 2.8:2, 10”x8” is 5:4
and A4 is 2.8286:2.
Whoa!
Too many numbers! And none of those numbers matter to us because
Photoshop will let you crop and size things in centimetres, inches or
pixels.
If
you're going to set a picture as wallpaper on your PC, it's wise to
crop and resize your picture to exactly the resolution of your
screen. This saves your computer from having to hold a bigger image
than necessary in memory the whole time. It'll make a tiny difference
to the performance of your PC that you'll never notice but every
little helps, right?
If
you're going to post a picture on Facebook, aspect ratio doesn't
matter at all but size does so read on anyway.
So
far, I've been using the Crop tool in the 'image' menu. It's just a
button that crops down to whatever you've selected using the marquee
(that dotty rectangle) tool.
Now,
because I want to resize the photo to use it as HD wallpaper, I'm
going to use two different tools. Bear in mind I have already cropped
this picture but I still have 7 million pixels: about 3 times too
many.
First,
the Image Size tool pops up a box with the actual size of the image
(obvious really). My test image is 3560x2072. My screen is 1920x1080
so I'll change the 3560 to 1920. That gives me a size of 1920x1117.
That's fine. I want an image that's exactly the right size in one
direction and not too small in the other. If you do get an image
that's too small in the other dimension, just do it the other way
round: setting the height exactly instead of the width.
Click
on 'OK' and we have a smaller version of the image but it's still not
exactly the size we need.
A
note of caution: If you're preparing an image for printing, check
that the dots-per-inch value is high enough. My pictures seem to
default to 96dpi and I routinely double this to 192dpi if the picture
is going to end up on paper.
Be
aware that when you change the dots-per-inch value, the dimensions
change automatically. A 96dpi image 4000x3000 pixels, when changed to
192dpi, resizes itself to 8000x6000. This is not useful so I always
manually reset to 4000x3000 (or whatever the numbers really were),
before clicking OK.
You
can set a higher dots-per-inch value if your printer is particularly
good but there is very little point in going higher than 320dpi.
After that, you'll not notice any improvement in quality but will
notice it takes considerably longer to print out. The online
printing services generally recommend that you send them images at
300 dpi.
The
second tool we need is the Canvas Size tool. This is an alternative
to the Crop tool that allows us to specify dimensions instead of
selecting free-hand. It'll also allow you to choose to crop all
around or anchored on any one side or corner of the image.
You
can also use this tool to add more width or height as blank space on
any edge of an image. That's another of those things we'll see later.
The
size of the image is shown in centimetres (on my version of PS). No
problem. The units have a drop-down menu. Just change it to pixels
because that's what screens are measured in. Remember, centimetres
and inches only matter on paper. On your phone, your tablet, your PC,
your TV, your digital picture frame, your facebook page or any other
digital medium, pixels are the unit of choice.
Meanwhile
back in Photoshop, we were trying to crop and resize to make an HD
wallpaper image.
In
the Canvas Size tool pop-up window, we should have dimensions of
1920x1117 again. Change the height to 1080 and click OK. PS will warn
you that you're about to lose a bit of the image. It's not an error
message! Click 'proceed' . Voila! A perfectly sized wallpaper image.
 |
| Mallard Duck coming into land on the Brick Pond |
Cropping
is also handy, as demonstrated earlier, after rotating an image.
Conveniently, that's what I'm going to talk about next.