Yeah, if you used pentax metadata to back up this observation even it will say the 50-135mm 2.8 is instead a 75mm-202mm f2.8. Last year I was still shooting film via Pentax ZX-L and 6mp K Mount. Same lens on each platform. I disagree that aps-c lenses magically grow longer with "telephoto effect". I like the term "Isolated View" better. Thats actually my term based on what I've seen comparing my 400mm 5.6 SMC-A on both platforms. For me I still see things in the 24x36 format. And More so now since I added two full frame 5D dslrs to my bag. What pentaxians really need is a body like ZX-L to see these results for themselves. I'm likely one of the few who, when i still had a Pentax rep last fall, used all his SDM lenses on my Pentax ZX-L film body and I know first hand the poor edge qualities and worse: Vignetting the non full frame SDM lens line provide via full frame film.
So its perfectly fine by me if people everywhere think pentax aps-c lens is made for full frame too. Having made the film body and dslr comparisions myself answered my own concerns and this was one of the few reasons I choose to add eos full frame to my 2008 equiptment bag.
Since pentax has pretty much killed the full frame 24x36 dslr I'd say the "telephoto" effect myth will persist since hands on comparisions require one to buy a newer pentax film body to see what full frame really provides via SDM lenses. There is no additional reach via aps-c format, just a cropped down Isolated Image instead.
Me I'm right on the edge of wanting to recoup my 6 year investment in pentax system primarily due to pentax trashcanning the 24x36 format. The one thing stopping me is the ever decreasing price on K20D out of Canada. Even B&H in NY is at $999 plus they're throwing in a $100 gift card plus free usa shipping. So $899 in NY versus the $720-$760 K20D I've seen K20D are selling for in Canada. If K20D makes it down to $600 or so new in the box I'd likley regret NOT getting what I really think may become Pentax' FlagShip Dslr as nothing better will get offered. Pentax has had two dramatic quarterly losses and now with markets the way they are alot of businesses are failing. It was tough on Pentax' bottom line before they got bought out for their medical division in april 2008 and then the credit markets seized. Things are still dropping, and seeing the K20D price declines in canada market I can imagine K20D will become known as Pentax dslr Flagship as nothing better gets issued from them.
For me I am quite unhappy Pentax choose to make a low end body versus the often rumored full frame k Mount. So many credible rumors on this forum turned out completely wrong. So either Pentax got told "No" by Hoya or no one on this forum no one really knows whats up Pentax Future Product launches and the rumor mongers are doing like I am, Just Guessing & then Wishing for Full Frame.
So bottom line (for me):
Isolated View provided by a lens like 50-135mm SDM is not the same complete view and added reach provided by 80-200mm 2.8 FA ,even though the K Mount dslr Metadata says it is. So comparing the weight of both isn't valid since they are not the same. One is aps-c and the other is full frame.
Originally posted by NickC The Pentax DA* 50-135 f/2.8 is a more valid comparison due to the crop factor, and this weighs 27 ounces including the hood. Substantially lighter and most likely smaller (I don't know the Canon lens), and of course includes stabilisation (in the body).
I do know that I can print Super A3+ prints from my K20D and keep forgetting to sharpen in Photoshop they're so good. I don't think I need to carry any extra bulk or weight to get superb images.
Nick