I would say that normally, usually, prime lenses are likely to be sharper than zoom lenses. Not only the sharpness, contrast and other lens flaws are minimized in prime lens. This is due to how prime lenses are designed to work with a specific focal range, contrary to zoom lenses to which the performance is usually varied between the lens' focal range. In other word, it's a compromise between the image quality and the effective focal range. For example, among the zoom lenses, it's well-know that an all-purpose/travel zoom lens like M.Zuiko Digital ED 12-200mm F3.5-6.3 OM (24-400mm full frame equivalent) will not have a good image quality overall. Moreover, a lens like this is usually very dim, as the aperture may run out prematurely, in this case, the maximum aperture is already at F5.6 at just 45mm focal range, even though it starts at F3.5 at 12mm.
However, it's worth mentioning that the lens is not a pro lens by any mean. But there are a few exceptions like Lumix 14-140mm F3.5-5.6, or OM's 14-150mm F4.0-5.6 II and 75-300mm F4.8-6.7 II. Even though these lenses are not pro grade lenses, but their image quality is among the best in m43 zoom lenses. And there's also M.Zuiko Digital ED 12-100mm F4.0 IS PRO OM, which is a pretty sharp zoom lens, if not the sharpest in this focal range (above 100mm, 150-400mm F4.5 TC1.25X IS PRO OM is the king, obviously 😅).
Therefore, with the advancement in modern zoom lenses, using a zoom lens is not a compromise anymore, especially in longer focal range. I would say that it's more practical because you can't zoom with your feet at longer range.
With all that said, today, I will compare one of the holy trinity pro zoom lenses, M.Zuiko Digital ED 12-40mm F2.8 PRO, versus a cheap prime lens, M.Zuiko Digital 45mm F1.8. Let's find out the result.
Foremost, I will not test the lenses for their distortion, chromatic aberration, vignetting, etc., as these issues are fixed automatically by in-camera's JPEG engine, or they can easily be fixed in post if you shoot RAW. On the other hand, lens sharpness and focusing performance can't be fixed. Therefore, I will focus on the sharpness and the autofocus capability. I will also talk a little about the lenses' contrast and their color rendering, as these are important characteristics that, while can be altered in post, could take some efforts and time. Without further ado, let's do this 🥳
Wow! What a surprise. 45mm F1.8, a cheap prime ($399) destroys 12-40mm F2.8 PRO ($999) completely in terms of sharpness. I know that there's no way to compare both lenses directly, since the comparable focal range is different. But the difference in their focal ranges (5mm at the longer end) should not translate to this much of the sharpness difference. And this comparison is around the center of the images, so... the result is pretty clear without any shade of doubt.
To clarify, I bought both the lenses at the same time. 12-40mm came as a kit with my E-M1, and I bought 45mm separately. Both have no issue with dust, fungus, and have never been cleaned due to those issues, so the coating remains intact. I shot the comparison images at the same time, with lens hood and front UV filter on. I also tested the 12-40mm shot without the front filter, but I see no apparent difference. The shots were taken at F5.6, eliminating any focus missing issue.
Therefore, the remaining question, is my 12-40mm copy a dud? As every reviewer on the internet would tell you that 12-40mm is extremely sharp, not a blurry lens by any mean. That's why I compared many of my 12-40mm shots with the sample shots of this lens from Digital Photography Review AKA DPReview. I see no apparent difference in terms of sharpness with my copy. So, my copy definitely is not a dud or a bad copy.
However, I found out that the sharpness of both lenses is nearly identical within close-mid focus distance. Let's see from the example shots below, side by side:
As you can see, when it comes to close distance focus, the sharpness between the 2 lenses is almost identical. I would give an edge to 45mm if an extreme pixel peeping is performed, though. But I find it negligible most of the time. As shown on the above, the difference in sharpness between the 2 lenses are much more pronounced when the focus distance is far away.
It's still amazed me how good the cheap prime from Olympus/OM System is. And the 75mm F1.8 would kill these 2 lenses on the spot, and there are the trinity F1.2 primes. Therefore, I will conclude that there's no way zoom lenses could hold a candle to prime lenses at the same focal range, regardless of the lens' pro status, at least, from within Olympus/OM System standard.
As one of the few 6 lenses that are compatible with OM-1 mark II's and OM-3's 50 fps sequence shooting speed, it's no surprise that 12-40mm destroys 45mm in this category. I have been using the 2 lenses for more than 10 years now, I would say that 12-40mm is noticeable faster in terms of focus speed, especially in dark places where 45mm would hunt a lot before getting the focus, while the gap is closer in well-lit places. Focus speed is everything between getting and not getting the shot. It is, therefore, an important aspect of a good lens.
Both lenses have nice contrast and color rendering. They are almost identical, as expected from Olympus/OM System. But I would give an edge in this category to 45mm.
Each lens has its pros and cons. There's no best lens. Practicality goes to 12-40mm, due to it covered range, fast autofocus, and weather sealed build. Image quality goes to 45mm. Fun factor goes to 45mm because it weights a lot less, more true to m43 philosophy.
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This is it for today. Thanks for reading. Now, I am waiting for my new lens, 14-150mm F4.0-5.6 II 😁 I will definitely review the lens after using it for a while. See you guys and gals again next time 👋
