Advantages of a Prime Lens

I have mentioned earlier about the advantages of prime lenses while traveling overseas but I will reinforce it in this article.  I find that all the same advantages apply even while walking around town or on country lanes or on the paths here in Homewood at Plum Creek.  Having a prime lens on the camera reduces the weight and bulk of the camera-lens combination and increases the quality of the images.  This is due to the design advantages for a prime lens.  They use less glass and don’t have the built-in zoom mechanism thus enabling the designers to better optimize the image quality (IQ) while keeping the weight and size smaller.  But, I need to remind you that to take advantage of this you need the higher number of pixels in late-model cameras, and if you are taking it to the extreme, you need to view the pictures on your computer or projection device and not make large prints.

I took the following picture on my Pentax K-5 which with 16 mp gave me a picture of 4928 x 3264 pixels.  The picture was taken with a prime 50 mm lens (effective 75mm) at ISO = 100, f/5.6, and 1/1000 sec.

Assume for the purpose of this article that I was curious about what was at the base of the trees.  Since I didn’t have a zoom lens on the camera, I couldn’t zoom in closer, and since the farmer was working right close to me I didn’t want to tramp across his field.  My alternative was to crop-zoom the picture on my computer after I had down-loaded the picture.  The following picture is a 1018 x 674 crop of the above picture.  As you can see it really makes a difference and I went from an area of 16.08 mp to 0.686 mp … quite a reduction with very little, if any, perceived reduction in IQ.  You can click on the pictures to see them larger, but they have still been reduced for display in this blog.

And there are other benefits.  The 50 mm lens is an f 1.8 lens and my 55 – 300 mm lens is an f 5.8 at the far zoom range so I achieve a significant increase in low light level capability with the prime lens.  In addition, the 50 mm weighs 122 grams and the 55 – 300 weighs 440 grams … and the 50 mm lens only protrudes about 1.6 inches in front of the camera while at 300 mm that lens protrudes about 7 to 7.75 inches.  Which would you prefer to carry … or have pointed at you if you were on the receiving end?

Don’t get me wrong, I don’t always use a prime lens.  I enjoy the ability to compose my shot with a zoom lens.  I can also crop zoom pictures taken with my long zoom lens even at 300 mm, but the quality isn’t as good.  If I’m walking where it is likely that I will see wildlife, I prefer to have a much longer lens than the 50 mm, but lately I have had back problems and have been almost exclusively using my prime lenses to reduce the weight of my camera-lens combos.  I either use my Fuji X100 with its effective 35 mm lens or my Pentax K-5 with the 50 mm (effective 75 mm) prime lens.  I’ll also mention that it has occurred to me that if I get a new camera with even more pixels, and/or a larger sensor, and a prime lens, that I might even do better. … maybe the new Sony RX1 ?

But don’t forget that I am talking about viewing the pictures on a computer monitor.  If you were to print the picture at 240 px per inch, the resulting size of the print would only be roughly 4.25 inches by 2.8 inches.  I don’t print my pictures but even I would be concerned about the small size of the picture in some cases.  For example, the newer tablets and monitors have much higher resolution.  There may come a time in the future that you would find the above picture too small.  That is one reason that I have generally limited my pictures on this blog to a minimum of 2000 px long on the widest side … and I may increase that in light of the latest Mac Reticular screens.

If you are interested in using prime lenses to reduce the weight and bulk of your system, I urge you to read about  street photographers since they tend to use primes lenses.  You might wish to first read my article about the similarities of street and travel photography by clicking here.  I would also encourage you to check out other articles on the web.  A recent good summary of street (urban travel) photography can be found by clicking here.

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