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04-26-2010, 03:37 PM   #46
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QuoteOriginally posted by wlachan Quote
When that lens is engaged in macro mode, it cannot zoom. For this reason, whether the lens was para or vari is invalid to that macro mode. You might also consider the macro mode a bonus.


Are you sure about that? I can move mine from 35 to 105, In macro mode, just as when not in macro mode. Or are you calling the change in focal length in macro mode something Other than zoom??



04-26-2010, 03:59 PM   #47
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QuoteOriginally posted by JeffJS Quote


Are you sure about that? I can move mine from 35 to 105, In macro mode, just as when not in macro mode. Or are you calling the change in focal length in macro mode something Other than zoom??

OMG you are right! The last one I had was more than a decade ago. My memory is cheating me.
04-27-2010, 10:55 AM   #48
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Sometimes (but rarely) I DO let the snark out. Usually it goes right back in.

QuoteOriginally posted by hangu Quote
I'm going to reiterate what I've stated earlier, I respect what you have to say and I have genuine respect for your knowledge of Pentax lenses. As such, I didn't want to argue with you or a Pentax manual. That wasn't sarcasm or obsequiousness.

My previous response was an attempt to ask you to clear up your comment. Not a sarcastic retort establishing my superiority on this subject (of which, I've freely conceded to you twice in this thread). I have a firm grasp of what a parafocal/varifocal lens is, I just wanted to know how a lens like this would be categorized since it has aspects of both.

I may deserve a snarky or even a rude comment from two other members on this thread, but certainly not from you. I've shown you nothing but the utmost respect for what you have to say.
OK - I stand apologetic for misinterpreting. I don't consider myself an expert by any means. I have collected over the years some paper and have read incessantly on Pentax. I received a KX & 50/1.4 as a college graduation present in 1977 and an MESuper & M-50/1.4 kit in 1984. I have played the buy-try-sell game since about 2003. Right now I am in sell mode again.

It should be apparent that in all these comments I haven't written about images. I don't have a scanner but I could have mounted the 35~105 on a digital body and shot some samples.

My position is simple. In 1983 Pentax described the lens as a 35~105 zoom lens. It qualifies as parafocal (apparently none of them perfectly maintains focus, but this one is close enough) when operated in normal mode. Pentax described a 5 foot minimum focusing distance in technical tables. Pentax recommended zooming in to focus and zooming out to compose.

I consider macro mode to be a specialty setting that mechanically alters the lens design The use of macro mode is not necessary to the ordinary operation of the lens. As such I argue this should be considered, for this discussion, a different lens when in macro mode than when in normal mode, but that is an opinion, not based on fact or convention.

With that constraint I submit this is a parafocal lens.

I agree an argument could be made that since the macro setting is possible, and zooming is possible when in macro mode, and the lens is varifocal when zoomed in macro mode, the lens is not perfectly a parafocal lens under all conditions.

Last edited by monochrome; 04-27-2010 at 11:05 AM.
04-27-2010, 11:44 AM   #49
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Hi - I have little to contribute in terms of the detailed discussion recently in this thread, but thought I'd confirm that I've just put my copy of this lens on my camera, and can confirm that mine does retain focus all the way from 35-105mm with little need for anything other than the tiniest hint of a correction. I didn't bother checking what happens in macro mode. I would have thought that a little bit of correction should be acceptable, but if the lens is completely losing focus then it may be that something isn't quite right.

Hope this helps with the original question!

05-28-2010, 05:44 AM   #50
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Hey, sorry for reviving an old thread but I've done some testing...

I recently got hold of one of these, but unfortunately it's one of those defective samples. I will try to describe the behaviour of the lens. It doesn't solve anything though and other samples of this lens might not show the same symptoms, but i wanted to share anyways.

First thing to notice: Focusing at 105mm and then walking to the wide end works. It does remain focus, if not perfectly at least decently. Problems occur when going the other way, ie from wider to narrower angle. Focus is lost going this way, but actually the closer it gets to 105mm the better it gets. Back to 105mm the focus is perfect again. When focus is lost because going from narrow to wide, I can at any time change direction and the focus gets much better (but still not so good). Note that it's important to hold the camera with the lens parallel to the floor (continue reading).

Second thing to notice: As with the test above, this test has more effect in wider angles. Tip the camera upwards, so that the lens is pointing at the roof. Now I can see that focus is completely off. Tipping the camera down makes focus a little off, but much better than after tipping it upwards.

I have only tried this at focus distances around 1.5-2.0m, and I'm also certain that the focus ring has not moved during the tests. Maybe someone can get something out of this?
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