Cropping
What is important in your picture
Cropping is a very interesting processing skill to learn. Normally you try to frame your pictures right. But if you are aware of how you might crop the picture, you may stop obsessing about framing (or zooming).
The first thing to realize is that you will not need all the pixels that you acquire in your image. Just take a look at Images for Print and Posters to get an idea. While there is nothing wrong with taking properly framed shots, sometimes you can realize that if you can not get close or you do not have the right focal length with you, just mentally being able to accept that you will crop the image later is a key skill that will help you.
In this way, you will be able to frame the picture so that it can be later cropped rather than actually trying to get it right at the time.
Of course people also crop pictures to get rid of things they did not want in their shots, there is nothing wrong with that, but once you realize that a 20 Megapixel camera takes shots that are if not 5 times at least 2 times larger than most needs, you will be more free. Once you experiment with this, you will realize that a zoom while practical is not that necessary.
Basically, when you use a 20 Megapixel camera:
- crop by 2x results in a 10 Megapixel image, focal length goes up by 1.4x
- crop by 4x results in a 5 Megapixel image, focal length goes up by 2.0x
As long as you have a sharp image, these are still more than you need for most purposes. So if you have a 24mm lens, you also cover pretty much anything up to 50mm just as well. And unless you are a bird watcher fanatic, a 200mm lens is just as good as a 300mm lens from a practical point of view.
This is a shot made with a Nikon Z FC using the Nikon Z 16-50 of some small chips in a carrier tray.
Take a note of the rectangle that shows the crop I have used. The resulting picture is below
The original cropped picture was 1529 x 1122 pixels (it is slightly scaled for this site), this is actually only 1/12th of the original picture. In the end, I needed a picture for a social media feed and this one had more than enough resolution, had good colors, good light, good angle and was just as sharp as pictures I took with a macro using a tripod. If you look at the numbers, the crop is what you would get from a 200mm to 300mm lens.
In the following table, I compare the resolution of a crop from a Nikon D700 with 12 Megapixels using a Nikon 35 that would correspond to the same field of view of different focal lengths.
| Focal length | X pixels | Y pixels | Megapixels |
|---|---|---|---|
| 50mm | 3098 | 2061 | 6.3 |
| 70mm | 2253 | 1499 | 3.3 |
| 85mm | 1869 | 1244 | 2.3 |
| 105mm | 1525 | 1015 | 1.5 |
| 200mm | 805 | 536 | 0.4 |
This means that I can crop a picture out of the one taken with a 35mm lens using a relatively old digital camera that corresponds to what I would see with a 105mm lens and still have a larger resolution than I use on these webpages (1280x850) and I would have to resize, who needs a zoom, when you can crop. Of course this requires that your 35mm shot is quite sharp if we need to make every pixel count.
This should give you a scale of what is possible with cropping.
This is maybe a forced example. I sometimes try to challenge myself, and take interesting combination of body and lens for a day trip. This time I had a manual focus Nikon 180 on a Nikon D850 which has over 40 Megapixel resolution. On a hike I ended up with this picture
It does not really look that interesting at first sight. The Nikon 180 is an excellent lens, but with a minimum focus distance of about 2 meters it is the furthest thing from a macro. But if you have a calm hand, good light, a bit of luck and maybe some experience, you know that you can get a pretty usable picture of the blue flower when you crop this. Question is how good can a tiny piece of the image be
Now this crop is 1280x1280 from the center which is pixel for pixel from the camera, no enhancement nothing. This is as good as I could get if I was using a macro as well. Now the question is, where will I use the picture. For a 2m poster probably the macro would be better, but for everything on social media, the web even reports and presentations, this is more than enough.
These pages are for Amateur Photographers and not really for seasoned photographers and professionals. I have no affiliation or commercial interest with any brand/make. I write from my own experience. I ended up using mainly Nikon, so I am more familiar with this brand than others. See price for notes on pricing as well as photography related links.