EF-S 18-55mm STM kit lens is sharper than 17-55mm/2.8 - Photozone.de data

The 17-55mm/2.8 is a fast, high quality and expensive lens that came out around 9 years ago. A lot has happened to lenses since then. In particular, Canon has come out with a line of very sharp and well performing STM lenses, including the humble and ubiquitous 18-55mm STM kit lens.

Photozone.de has tested these lenses (and many more), and published resolution figures for them. I decided to plot the data up on graphs to make it easier to compare them. The graphs are included at the end of this post.

For those who are not at home scrutinizing graphs, I summarize the findings in words below.

The first graph shows the results for the center of the image. It shows sharpness curves for both lenses for a range of apertures and for a selection of focal lengths, which happen to be the focal lengths tested at PZ. The curves show that at a focal length of 17 or 18mm, the 17-55 is slightly sharper. The peak sharpness of the 17-55mm happens at f/4 whereas the 18-55mm lens peaked a stop smaller, at f/5.6. For all the other focal lengths, the 18-55mm kit lens was a bit sharper. In each case, the optimal (sharpest) aperture was one stop smaller for the 18-55mm lens.

Now on to the graph for the border of the image. At the border, the 18-55 kit lens again is generally a bit sharper for all focal lengths. The optimal apertures of the two lenses are closer together, differing by around 1/3 stop.

So overall, the expensive 17-55mm lens is a bit less sharp than the 18-55mm kit lens. To get the best center sharpness from the 17-55, shoot at f/4. For the 18-55, shoot at f/5.6. For best border sharpness, stop either lens down another 1/2 or full stop.

I own both lenses and have compared them in shoots. I can affirm that my copies behave essentially as described by the PZ data. A couple of example shots are included in my POTN review of the 18-55mm STM lens.

Reminder: There are many properties of lenses that are important besides sharpness. They include build quality, light transmission, color, bokeh, chromatic aberration, vignetting, and distortion. Fortunately, these days the latter three qualities are easy to correct in post-processing, and therefore less importance can be accorded them. Autofocus performance is also important, and it should be noted that some users have reported problems with the 17-55mm/2.8 when shooting at distances.

I think most people would be better off with the 18-55mm STM kit lens, unless they require the fast aperture of the 17-55mm/2.8.

Archibald, thanks for posting this. I have the 18-55 STM lens and I've been very impressed with it. I also have its "big brother", the 18-135 STM, which I recently took on vacation. It's no slouch either.

Many of the consumer grade lenses Canon has introduced within the past five years have been truly amazing. It's a testimony to their optical design and manufacturing processes that these lenses can provide such high image quality at such affordable prices. They're challenging many old stereotypes about the optical quality of "kit" lenses.

Mike

Archibald,

I am happy you did the investigation for yourself, when I mentioned the 18-55mm STM was actually outdoing the 17-55mm USM, other than not being able to do F 2.8. I really like your easy comparison graphs! Good show! https://photography-on-the.net …showthread.php?​p=17520364

anscochrome wrote in post #17680495
Archibald,

I am happy you did the investigation for yourself, when I mentioned the 18-55mm STM was actually outdoing the 17-55mm USM, other than not being able to do F 2.8. I really like your easy comparison graphs! Good show! https://photography-on-the.net …showthread.php?​p=17520364

Thanks for the reminder. There is little new under the sun.

But even after all this time, after all the reports, we still get members complaining about poor sharpness from their kit lens and wanting to buy an expensive replacement EF-S or an L lens. The purpose of the graphs was to try to make the comparisons more approachable.

Archibald wrote in post #17680499
Thanks for the reminder. There is little new under the sun.

But even after all this time, after all the reports, we still get members complaining about poor sharpness from their kit lens and wanting to buy an expensive replacement EF-S or an L lens. The purpose of the graphs was to try to make the comparisons more approachable.

I would say it is high time for Canon to give the 17-55mm F 2.8 a refresh, especially considering the 18-35mm F1.8 Sigma exist, which for about the same money, kicks the Canon across the pond! (yes, I realize it does not do 36-55mm) For me, I'd rather switch to a prime ( like the 24mm F 2.8 EF-S) id I really needed the aperture, but I am so pleased with the ISO 6400 performance of the Rebel T6S, I have not felt the need to resort to primes.

The Rebel T6s is pretty noisy at ISO 6400, but it does not have purple blooming in the shadows like my 5D2, so I have been living with F5.6 and assistance from IS on the three kit lenses. A bump of +20 Noise Reduction in Lightroom (Luminance), has made ISO 6400 shooting with it right as rain for me

How many of these threads did you make? Next time maybe just make one thread. Which one is sharper @ f/2.8. Oh right...