Originally posted by northcoastgreg
The DFA* 50 is probably being designed by Masakazu Saori,
He's done some nice lenses. But my observation is that the Tamron, Canon and Nikon 70-200 have all been about the same overall, (Sigma was not included, they refused to lend the testers a copy). I have seen no independent review suggesting the Pentax 70-200 is better than any of those, to make up for it's undeniable increase in weight. Maybe you've seen something I haven't?
I'm hoping to find some evidence to support the idea that they didn't make a heavier lens to achieve the same result. You always want the "latest greatest" to prove to be better than what came before it, especially if it's adding weight.
Unfortunately most sites are pretty spotty at including Pentax in their new lens evaluations. Not a mention of the 70-200 at Imaging Resources, DxO or Photozone or any of the sites with good benchmark information comparing a lot of both legacy and modern lenses.
---------- Post added 07-26-17 at 02:29 PM ----------
Originally posted by Rondec
I don't understand why people feel like it is harder to build a big 50mm lens than a small one. I would think it would be easier to control vignetting, distortion and make the corners sharp, if size were no object.
It would be, that's why we are willing to pay a premium for lenses like the 31 and 77. At a time when everyone else is using technology to shrink product while maintaining value, camera companies seem to be doing the opposite, claiming they have to increase size to increase value. I'm not willing to pass judgement, i don't know enough to, but that doesn't mean I'm willing to just give in and say bigger is better, or give the bigger is better guys a free pass. The idea that smaller can be just as good is much more appealing.
Back when I was playing baseball, over 10 years I went from using a 34 once bat to a 30. It turns out bat speed is more important than the weight of the bat, if you can't get the 34 up to a descent bat speed in the 1/4 second you have to swing, you'll do better with a smaller bat. I'm sure there are lots more examples where bigger is worse, not from a theoretical viewpoint, but from a practical standpoint.
For me, if it's bigger it has to be better. Now, show me how it's better. I'm not going to buy a bigger lens just to placate some lens designer's compensation issues.
When the 31, 43 and 77 came out, they were smaller and better. What's changed that that can no longer be done?
I'm wondering if it's that there is a segment of the market that will consider a large lens a better deal than a smaller lens with the same or very similar photographic qualities. Like the really big cars of the 50s-70s. You certainly see that when comparing the 31 ltd and the Sigma 30 1.4. You really don't get anything comparing the two, for all that extra size and weight of the Sigma, but some people prefer it, I suspect, just because it's big.
I'm willing to bet it's the same as it always was. You have to like the way the lens renders. Bigger or smaller probably has very little to do with that. One has to ask, does Pentax still have the ability with it's designers to produce high quality light weight lenses? Is the current trend to "bigger than the competition" a result of falling behind in a specific area and trying to catch up, or is the high quality small lens a thing of the past? As Rondec pointed out, it's easier to do bigger, but does that mean it's impossible to do smaller? Finding an acceptable compromise between weight and optical quality is an art in itself I would propose. The current philosophy would suggest it's easier to just go big and forget about whether or not folks can actually carry the lenses.
Are the new lenses better, or just cheaper to manufacture using modern technology?
If you have trouble with weight, go 4/3s (many already have) ... I'm sure its a viable option, and one where designers are still making an attempt to keep the size down. But I don't see how that helps Pentax.