I have compared two Canon lenses, the 10-20mm f/3.5-4.5 consumer zoom (on APS-C) and the 16-35mm f/4 L IS here. The results were predictable - the L zoom was consistently better than the consumer zoom, at about three times the cost (and increased weight).
Also, I used to collect old, Pentax screw mount manual focus lenses. These old lenses have a cult following, with various miraculous attributes being ascribed to them (glorious bokeh, an otherworldly quality of the image, etc. etc.) While some of these old lenses (particularly the old Leica lenses) do deserve the praise, I had always wondered how these old lenses compared to modern, non-consumer grade ones.
So in this post, I compare the older, non-IS Canon 70-200mm f/2.8L zoom with a decades-old, manual focus, Pentax screw mount 200mm f/4 Super-Multi-Coated Takumar. The comparison was done at f/4 (since the Pentax manual focus prime cannot open up to f/2.8) on a Canon 6D, which should have plenty of resolution. The target image was a neighboring building at (close to) infinity focus. The Canon zoom was auto-focused, while the Pentax was manually focused using Live View (it ended up at the infinity stop anyway). Base ISO was used and a fairly high shutter speed (1/2000 second) on a tripod.
First the full image:
Also, I used to collect old, Pentax screw mount manual focus lenses. These old lenses have a cult following, with various miraculous attributes being ascribed to them (glorious bokeh, an otherworldly quality of the image, etc. etc.) While some of these old lenses (particularly the old Leica lenses) do deserve the praise, I had always wondered how these old lenses compared to modern, non-consumer grade ones.
So in this post, I compare the older, non-IS Canon 70-200mm f/2.8L zoom with a decades-old, manual focus, Pentax screw mount 200mm f/4 Super-Multi-Coated Takumar. The comparison was done at f/4 (since the Pentax manual focus prime cannot open up to f/2.8) on a Canon 6D, which should have plenty of resolution. The target image was a neighboring building at (close to) infinity focus. The Canon zoom was auto-focused, while the Pentax was manually focused using Live View (it ended up at the infinity stop anyway). Base ISO was used and a fairly high shutter speed (1/2000 second) on a tripod.
First the full image:
The highlighted areas are zoomed in (1:1) for comparison. They roughly cover the center of the frame, and the edge. The extreme edge was not used, because it turns out the Canon 70-200mm zoom is not really 200mm at the long end (it is a bit short).
Let's look at the center of the frame, where both lenses should be performing their best. The zoom is one stop down, so should show improved performance.. but it's a zoom, while the competition is a (wide-open) prime:
Canon 70-200mm f/2.8L at 200mm f/4, center:
Pentax 200mm SMC Takumar at f/4, center:
We can see that the Pentax is ever so slightly longer than the Canon, it has less contrast, and is less sharp. We're talking a $40 lens (at KEH) versus a $1300 lens. I wondered if the Pentax was not critically focused, but it was at the infinity stop, and Live View could not yield a better focus. In any case, "in the field" one would not have the luxury of tripod and Live View and would probably just use the prime at the infinity stop.
The difference is certainly obvious at pixel-peeping distances, but on a regular full-size image the two lenses would be indistinguishable.
Canon 70-200mm f/2.8L at 200mm f/4, edge:
Pentax 200mm SMC Takumar at f/4, edge:
again we can see better contrast with the Canon (better coatings perhaps) and also more detail in the fine vertical lines of the blinds. What is noteworthy is that both lenses don't really suffer much (if any) drop in resolution, going from the center of the frame to the (near) edge.
Is the $1300 Canon a better lens? of course it is - sharper, more contrast, autofocus - but is it thirty times better? that depends on the user. If autofocus and zoom are important, then these are worth paying money for.
The Canon is quite bulky in comparison to the relatively compact Pentax prime, however.
I was whale-watching in Monterey in October 2016, and did not bring any long lenses (the Canon 70-200mm is very hard to travel with). Ended up with a lot of distant images of whales (using the 35mm end of the 16-35mm f/4L IS). At that time, I would have gladly used the small Pentax prime, in spite of all its shortcomings and non-L image quality.
In conclusion: yes, the Canon 70-200mm f/2.8L is a better lens at the 200mm end than the 1960's - 1970's Pentax 200mm f/4 Super-Multi-Coated Takumar. But the SMC Takumar is more than good enough and I would say can more than hold its own image quality wise (so long as you don't pixel-peep at 100% magnification).