From stitching big to cropping small: Where the images in the panoramas of my previous post featured a multitude of the MP (Megapixels) found in normal dslr images, today’s image, a female Costa’s Hummingbird, only has a fraction of my D300’s 12.3 MP:
To crop or not to crop
This image is a 22% crop, which means that it’s only 2.7MP. As you can see, even such a significant crop still produces an image that’s usable for web purposes. Some photographers try to convince others that cropping is bad. They think that you should just frame the image right from the start. While I agree that it would be ideal to do so, often it’s not only difficult, but simply impossible.
In this case for example, I had to work with my 70-200mm 2.8 lens. It’s the longest lens I own, and due to the low light conditions, I could not use my 2x teleconverter: Adding the extra glass cuts down the light reaching your sensor, resulting in two stops slower shutter speeds, which you can’t really afford with these lightening fast guys. Since the 200mm didn’t give me enough reach to get an image with a hummingbird filling the frame nicely, I had to the choice to either crop in post processing, or not take the shot.
Other than finding someone willing to give me a nice 400mm 2.8 to work with (please leave a comment), cropping is the only real solution for me in such cases. I couldn’t get any closer, as I was already hovering around the minimum focus distance of this lens.
As you can see, the amount of background in the original image is too much compared to the small subject. Although the eye is still drawn to the main subject, it’s too small and also placed dead centre (which is aesthetically not very pleasing, more on that in a post on composition later).
Although we’re all trying to get the best composition from the start, we don’t always succeed. Luckily you can shoot many images at hardly any extra cost in these digital days, but even then you might occasionally find yourself back home, looking at the screen and realising you didn’t get it right. Rather than having an aesthetically not so pleasing image, you can sometimes turn it into a great one by re-framing it in post processing. In today’s example I chose to shoot the subject dead centre, since the central autofocus point has the best performance in low light conditions and I knew I would crop the image later anyway.
Different aspect ratios
Most digital reflex cameras have a sensor with an aspect ratio of 2:3, just like how the film reflexes measured 24 by 36mm. However, for creative purposes it might sometimes be nice to have a different aspect ratio. The headers of my blog have a ratio of about 1:3 and some of the featured images in my second post 1:1 (square), simply because it works better from a creative point of view. Just because a sensor has a certain size, does not mean all our final images should have that same size.
Resolution vs. high ISO performance
Although the ability to do more aggressive cropping is one of the reasons to like cameras with a higher MP count, you should keep in mind that higher MP sensors perform less well at higher ISOs. On a higher MP sensor, each pixel is smaller than those on a sensor with less MP, making them less light sensitive and resulting in more noise at higher ISOs.
Nonetheless I’m really looking forward to the upcoming Nikon D800 body. It’s rumoured to have 36MP, which means that it’s low light performance (i.e. high ISO) will probably not be nearly as good as the Nikon D3s and D4. However, sensor technology and software have made huge advances in the last few years and the ISO performance will probably be at least on par with the 12MP D700. When you would shoot the full frame D800 in crop mode (DX camera size), you still have 16MP, 30% more than I have now on my D300!
If you haven’t got any alternatives, if it’s the only way to save an image already shot, or if you need to do it for creative purposes, cropping can be a great post processing tool. If you’re a professional, needing to print life size posters for a big client, this wouldn’t work of course, but for most other purposes I would suggest to add cropping to your creative toolbox. Do you agree?