It seems that the more that is written about any subject the more misleading things get. I read an article last week about a guy who did some testing with zoom lenses and prime lenses and a lot of what he said was true, but a lot was misleading so I wanted to go through what he said and clarify it.
First what is a prime and what is a zoom lens? A zoom lens is exactly what it sounds like, it is a lens that allows you to zoom either closer or further away when shooting. Some zoom lenses are 10-20, 24-70, 70 – 200, 150 – 600 and a lot of sizes in between. A prime lens is a lens that is not able to zoom they are lenses like 18mm, 75mm, 100mm, 400mm, etc.
So now to the article…. the article was about how prime lenses are sharper than zoom lenses, a fact that really has never been in question. A prime is so much sharer that in some situations it is scary when compared to cheap zooms. This fact is a fact and really cannot be argued. But instead of leaving it at that the article went on and on about charts, test results, etc, etc. This is where I get really upset… as a photographer WE ARE NOT SELLING TEST RESULTS!!!! We are selling images and if a zoom lens allows you to get a picture that a prime would not then WHO CARES ABOUT THE TEST RESULTS!
Many years ago a report came out from an expert about digital photography, part of the report read “In order to achieve the same quality that film offers in a digital print you will need a 400 megapixel camera for an 8×10 print AND if you want to go larger then 8×10 you will need a camera that is in the 1000’s of megapixel range”. When this report came out I was already printing up to 16×20 with my 6 megapixel camera and they looked great!! I went to a number of meetings that this scientific study was quoted as being 100% true and was even called a liar at one meeting when I showed a print from my digital camera.
At the same time another expert was talking about using the histogram on your camera and how you needed to have a perfect bell curve when shooting a image or the image should be deleted. I remember hearing a speaker at a meeting tell how he had yet to get a perfect bell curve so he had deleted all his images that he had shot digitally. I was shocked and when I tried to explain the histogram I was ignored.
Now I am not saying that in a perfect world that the two above situations are not true, but these are reports from a lab not the real world. Sure if you shot medium or large format negs, professionally developed them, and printed in a professional lab the resulting resolution when viewed under an electro-microscope may come out to 400mp for an 8×10 but how many people do this – I would say nobody in the real world. Likewise the perfect bell curve for a digital image is ideal but there are so many variables that to get that is impossible 99% of the time.
So it goes with this report on prime vs zoom lenses. In a perfect world using a prime is going to be better, but if using a prime means that you are not getting the correct cropping or you simply cannot afford to carry a bag full of primes then what good is this???
Once again we need to take more into consideration then the scientific tests, we need to take real world work into account before we come up with these reports!