Lens Quality vs. Camera Resolution

I have often heard comments such as “Wow, you can take photos of the moon with that”, “That is a really big lens/camera” when people see me with my camera. I most often have my Tamron SP AF 70-200mm F2.8 Di LD (IF) Macro lens fitted to my Sony A900 camera which is also fitted with a vertical grip. The Tamron 70-200 is a big lens for its focal range and when fitted to the A900 the set weighs in at an astounding 2.4kg. This may not sound like much, but carry that over your shoulder all day and you soon realize it is heavy! This makes a big and fairly heavy set, but why do I bother? Why not just use a smaller camera body and a small and light 18-200mm lens which costs less than half the price? Well, it comes down to quality of images I wish to produce with the option to enlarge.

The quality is in the lens

With a cheap 18-200mm lens I could still produce good images which will look identical to photos shot on the Tamron I use when uploaded to Facebook or when printed at 10X15cm (4″X6″), but once you start enlarging the images you soon see a difference. Even when you are perfectly focused on your selected point, a low quality (cheap) lens is never going to provide you the clarity you need for enlargements. A high quality (unfortunately also expensive) lens captures light with less optical distortion and dispersion which, when captured by a high resolution sensor, translates into a clearer image. This fact is not obvious when you print on small sizes or even upload the images to internet media such as Facebook since most of your uploads are low resolution. I could take a photo with my mobile phone and one with my top-end camera and the shot would look identical under certain conditions on Facebook, but as soon as you print an A4 enlargement the difference is huge.

Here is a sample of an image recently captured. The focus point I selected was the grooms left eye (on right of image). At full viewing size the image is good and one could argue that any camera could capture it like this. I could take a consumer grade camera from chain store and get a shot to look just as good, but would it enlarge properly? Click the image to get to the full resolution image to really understand this.

The Camera Body Captures Quality

I am sure you have heard the adage, “junk in, junk out” which is true for camera bodies. Even if you have the best quality camera in the world, if you fit a poor quality lens to it then the images will still not be that good. I would rather fit a great quality lens to a cheaper camera body than fit a cheap lens to a great camera body. The resolution of the camera means nothing if the light is passing through low quality optics which distorts and disperses it. If the optics provide you with excellent light then resolution of the camera will only determine the enlargement possibilities, not quality.

So why do people want high resolution cameras?

Most people want high resolution camera because of an oddity which occurs when you downgrade the resolution for display/print… fuzzy edges seem to become sharper!
What happens is that when you shoot an image with your 16mp camera fitted with a cheap lens and you upload it to Facebook it appears sharp and clear, but in fact the image is slightly blurry. This fact is not apparent because Facebook has dropped the resolution which compresses the pixels together and gives them the appearance of being sharper. However, when you print the image on A4 you soon notice that the image is slightly blurry.

This concept is sometimes difficult to understand so I will give an example. The image below is a representation of what you get with a low quality lens versus a high quality lens. The bottom half of this image shows what you would get from a low quality lens and the top half from a high quality lens. If you cannot see the difference it is because this is small image is displayed in low resolution as it would appear on a small print (10X15cm), but on A4 you will quickly see an image difference. To see this effect, click the image to view the larger size. It is exactly the same image and you are welcome to download this sample and test it at home. First print the image on a postcard size piece of paper (10X15cm) and then print it on A4 and notice the difference.

I hope that this article will give you a little more insight into why professional photographers spend so much money on expensive lenses and camera equipment and don’t just settle for those which you can purchase in a chain store.

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