Prime versus Zoom: Can You Tell the Difference?

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The first zoom lenses were not very good. Manufacturers of early zooms made optical concessions in the name of convenience and flexibility. The ability to change your lens’s field of view—eliminating the need to carry numerous prime lenses and swap them on the go—was, and still is, enticing to many photographers. Ever since the birth of the zoom, photographers have debated which option is better: fixed focal length prime lenses or variable focal length zoom lenses?

Note: This article was originally published 10 years ago. The text and images in this article have been updated.

Why did early zooms underperform and create an indelible reputation for not being as good as their fixed focal length prime siblings? Well, to get the light traveling through a zoom lens to behave properly when the focal length changed, optical engineers had to add more lens elements along with mechanical systems to move the glass physically. The greater number of elements and glass-air interfaces you have in a lens, the greater the chance for some undesired optical degradations, such as chromatic aberrations, distortions, softness, and more.

Today’s zoom lenses are better than ever, and many pros use zoom lenses exclusively—often never employing fixed focal length prime lenses. One can argue, however, that the same technology and manufacturing processes that have made the zoom lens better are likely making new prime lenses better, as well.

It was hard (impossible?) to “pixel peep” in the days of film, but now pixel peeping is a mainstream digital sport. If we compare a photo taken with a zoom lens to one taken with a prime, do we need to pixel peep to see the difference? Or is this a moot comparison in the modern photographic era? Is a zoom lens just as good as a prime?

Let’s take a look!

Example 1: Here we compare the FUJIFILM XF 35mm f/1.4 R against the “kit lens” FUJIFILM XF 18-55mm f/2.8-4 R LM OIS. For those unfamiliar with the Fujinon lenses, the XF 35mm is known not for its sharpness, but for having great “character,” and the 18-55mm is referred to, by some, as the “non-kit lens” as it outperforms entry-level kit lenses from other manufacturers. The images below were shot in raw format and processed identically—no unique adjustments to sharpness or color. Can you spot any difference between the two lenses?

FUJIFILM X-T3 with the XF 35mm f/1.4 (left) and XF 18-55mm f/2.8-4 (right) lenses, set at f/8, ISO 160. Identical processing of raw images.

100% crop

200% crop

Example 2: Here is another pair of images from the same two lenses.

Again, the FUJIFILM XF 35mm f/1.4 (left) and XF 18-55mm f/2.8-4 (right) lenses.

100% crop

100% crop

200% crop

Example 3: Here is one more pair of images from the same two lenses with a crop to show corner detail.

One more time: the FUJIFILM XF 35mm f/1.4 (left) and XF 18-55mm f/2.8-4 (right) lenses.

100% crop

Example 4: Just to mix it up a bit, here is the Nikon AF DC-NIKKOR 105mm f/2D lens going up against the Nikon AF Zoom-NIKKOR 80-200mm f/2.8D ED lens (no longer manufactured).

Nikon D300 with the Nikon DC-NIKKOR 105mm f/2 and the Zoom-NIKKOR 80-200 f/2.8D ED lens, both at f/8, ISO 200. Identical processing of raw images.

100% crop

Can you tell the difference? I cannot.

Even with the 100% crops, the images look identical. At 200% you might see a tiny bit of difference, but we are literally splitting pixels at that point—an absurd level of “pixel peeping.” There is nothing in these examples that would be discernable on a print, on the screen, or even on a billboard.

Granted, I am presenting images that were created in the heart of both the prime and zoom lens’s sweet spots (midrange aperture setting), but the results at other apertures were very similar.

So, if you cannot tell the difference between a prime and a zoom lens, why would you ever want to carry a prime lens (or multiple prime lenses) in your bag? I will give you a few reasons.

  1. Wider aperture. While there are exceptions, many prime lenses will have a larger maximum aperture when compared to even the most expensive zoom lenses. This wider aperture will allow you to create images with shallower depth of field, as well as photograph in conditions with less light.
  2. Smaller and lighter. A prime lens is likely smaller and lighter than a zoom lens of a similar focal length, albeit with only a single focal length. If you are trying to travel light and know the focal lengths you need, a bag full of primes is lighter than a bag full of zooms.
  3. Unique lens designs. There aren’t too many zooms around that can replicate the specialized effects of tilt-shift, macro, fisheye, soft focus, or other specialized lens types, which are integral to certain niche shooting applications.

My allegiance to the prime lens (see this article about the venerable 50mm lens) is public, but I still own and use zoom lenses from time to time!

What are your thoughts in the age-old debate of prime lenses versus zoom lenses? Let us know in the Comments section, below!

2 Comments

If you're going to compare lenses, don't do it at f/8.  Even a bargain-bin M42 zoom lens can look very good at that aperture.  Try these again at f/2.8 (or at least close to it) and differences in lens quality will become much more apparent.

Hi Ian,

You make a valid point there. This article was an update to an existing piece with, honestly, a horrid pair of photos. I did not know if the hundreds of comments left on the original article would remain, so I tried to keep the camera settings similar to avoid confusion.

This was not meant to be a scientific comparison as there are variations in lens performance of identical lenses due to manufacturing variations, so an apples-to-oranges test just shows the results for the lenses I have in hand.

To add a bit of variety, the second set of images were shot at f/4 (the maximum aperture of the zoom at that focal length) for a more "real world" comparison on the fringes of the lens's sweet spot.

Thanks for reading and thanks for the comment!

Best,

Todd

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