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04-03-2010, 10:12 AM   #1
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How come Pentax limited lenses didnt extend up to 100mm

Im just wondering why Pentax limited lenses didnt extend up to 100mm.
Can a prime like around 85-100mm at f2 or maybe f2.2 be made like the size and weight in between the DA70 and FA77. Maybe 4cm long, 200grams?

I notice the DA70 f2.4 is only 2.6cm at 130g.

04-03-2010, 10:18 AM   #2
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They do have the D FA WR 100mm F2.8 macro Limited now.
04-03-2010, 10:24 AM   #3
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Yeah but its a macro, 80.5mm long and 340g and f2.8
04-03-2010, 11:43 AM   #4
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I'd look at the M85/2 and M100/2.8 as models of what's clearly possible, and those are full frame lenses (see Welcome to Bojidar Dimitrov's Pentax K-Mount Page for specs on these and any other Pentax lenses). The M85/2 is right about where you're talking about. The M100/2.8 is noticeably longer, but still smaller than the macro. Still, that's an impressively small & light lens for a 100mm macro. I find it pretty unlikely they'd bother to release another lens in that same focal length. An 85 wouldn't be out of the question, but is that enough longer than 77 to really matter?

I'd actually think if they were to extent this lineup in this area, it would be to add a 120 or 135.

04-03-2010, 11:45 AM   #5
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QuoteOriginally posted by legacyb4 Quote
They do have the D FA WR 100mm F2.8 macro Limited now.
Legacy, that lens is not officially a limited one. Owners do say that with all the metal and refinement it feels like a limited one, though.
04-03-2010, 09:29 PM   #6
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The M85/2 is what im thinking the only thing lacking is that its a manual. Havent tried any manual lenses ive been trying to use the manual focusing on the AF lenses but its a bit hard to get it right
04-03-2010, 09:52 PM   #7
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QuoteOriginally posted by rustynail925 Quote
The M85/2 is what im thinking the only thing lacking is that its a manual. Havent tried any manual lenses ive been trying to use the manual focusing on the AF lenses but its a bit hard to get it right
it's really tricky especially if you combine a thin shallow DOF + small viewfinder. it is rather a hit or miss thing. really different when compared to shooting with a bigger VF.

I'm not quite sure what you are shooting with MF, but there are atleast things that you could use to make focusing much easier. use a tripod, and/or shoot live view mode. if these doesn't help nor ideal for the type of shooting that you are doing, a 1.36x magnifying eyepiece and a split-prism focusing screen combo would be very good and very helpful to use on the viewfinder.
04-03-2010, 11:11 PM   #8
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Also, MF is much easier using a lens designed for the purposes. The focus rings on AF lenses are generally way too loose and don't turn far enough - it's too difficult to control the focus precisely.

04-04-2010, 06:51 AM   #9
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QuoteOriginally posted by emr Quote
Legacy, that lens is not officially a limited one. Owners do say that with all the metal and refinement it feels like a limited one, though.
Beside size, it seems just like a Limited;
on the other hand 35mm Ltd is also macro and relatively bulky so maybe we can ignore the size : )

So why don't we pass to next step and look for a 135mm Ltd.

By the way, does anyone know how to calculate max. aperture for a 135mm lens with 49mm filter size?
04-04-2010, 10:30 AM   #10
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You mean like some sort of theoreticl maximum that could ever be produced? Not sure that's really possible, since as constant aperture zooms appear to demonstrate (see current thread on zooms faster than f/2.8), the physical size of the front element isn't the only determinant. but the fact that the only 135 I know of with a 49mm is the M135/3.5, and every f/2.8 or better 135mm I know has a larger filter size, I'd say f/3.5 is probably the largest that can reasonably be done, and if it possible to do any better, it's extremely unlikely it would be more than half a stop better.
04-04-2010, 12:18 PM   #11
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QuoteOriginally posted by rustynail925 Quote
The M85/2 is what im thinking the only thing lacking is that its a manual. Havent tried any manual lenses ive been trying to use the manual focusing on the AF lenses but its a bit hard to get it right
It's tricky to use manual focus on an AF lens. However, it's not that hard on a lens designed for manual focus. The truth is that I get more out-of-focus pics when using autofocus on DA 40 & 70 than when using manual focus with K 35mm F3.5 and M 85mm F2. I don't know why I suck at using AF lenses. It's not a BF/FF issue as I have tested it many times. However, if this continues I will end up with only MF lenses...

Kind regards
.lars
04-04-2010, 06:54 PM   #12
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I though its the same with AF lenses switch to MF.
Recercare - Isnt the AF accurate ? how come you get more out of focus pics in AF?

MF user do you have to magnifying eyepiece when shooting MF or it can be done w/out?
04-04-2010, 08:23 PM   #13
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QuoteOriginally posted by rustynail925 Quote
I though its the same with AF lenses switch to MF.
Recercare - Isnt the AF accurate ? how come you get more out of focus pics in AF?

MF user do you have to magnifying eyepiece when shooting MF or it can be done w/out?
it can be done without a magnifying eyepiece but it's quite a challenge or of discomfort especially with a small viewfinder and subject of distance. you can install and just leave an eyepiece or eyecup on your viewfinder. you don't need the long flipping one.
04-05-2010, 10:18 AM   #14
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QuoteOriginally posted by rustynail925 Quote
I though its the same with AF lenses switch to MF.
It's the same process, sure. But there's a huge difference in the actual experience. A MF lens has usually a focus ring that turns at least half a revolution, maybe 3/4, whereas the ring on an AF lens turns only a small amount. So with an AF lens, a tiny motion of the ring changes focus a lot, making it very hard to focus precisely Plus they are so loose that is hard to turn the ring precisely. Whereas with an MF lens, the ring offers much more resistance, making it easier to control the movement, and small movements of the ring affect focus only small amounts, making it much easier to fine tune the focus.

QuoteQuote:
Recercare - Isnt the AF accurate ? how come you get more out of focus pics in AF?
I can't speak for him, but I would say AF is accurate *if* it happens to guess right and focus exactly where you wanted. But even if you select a focus point yourself, that's not really a "point" but a "general area", and if you really want pinpoint the location of the focus, AF is not the best tool. Also, on cameras pther than the K-7, tungsten or other yellow/orange light will cause the camera to front focus. I pretty routinely turn off the AF when shooting in low light with large aperture / small DOF, as even with this lens and it's so-so focus ring, I can place focus more precisely by doing it myself than by hoping the camera will place it exactly where I want.

QuoteQuote:
MF user do you have to magnifying eyepiece when shooting MF or it can be done w/out?
It *can* be done without, but sure, the bigger the better, within reason. The cameras that have smaller viewfinders (eg, K-x, K-m, KxxxD) may benefit from a magnifier more than the ones with the larger viewfinders (K-7, KxxD).
04-05-2010, 10:22 AM   #15
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I am glad there is no 100mm Ltd, I have no more budget now...
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