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*ist DS manual focus lens selection...

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I'm not that familiar with the Pentax system. So please excuse what might be a beginner question for yall.

I don't have a DS yet. But I'm thinking the lenses now.

I understand there are Pentax-A, Pentax-M, Pentax-K? lenses. What are the real difference when mounted on *ist DS? Will they allow me to meter? What restrictions will I have?

What are the nice lenses (BOTH AF and MF) to start with (and cheap) in Pentax system? For example, in Canon you can start with 50/1.8 28/2.8 and 135/2.8 for less than $200.

How good is 50/2.0 compared to 50/1.7? I see lot of those on used market.

Thanks for the answers!
 
Ok, here we go again... (we have many threads on this)

K lenses - manual focus, mechanical aperture linkage.
M lenses - as K lenses, but more compact.
A lenses - added electronic aperture coupling.

Functions with the DS

K and M lenses - spot and centrumweighted metering will work with the camera in M)anual mode when you press the AE-L button (and if aperture ring usage is turned ON in the Custom setting menu, please refer to your manual, I don't have it nearby now). You also get in-focus confirmation (only center point). P-TTL flash doesn't work, only standard TTL. Program mode, aperture priority and shutter priority modes are not supported (but Manual mode with AE-L button is actually a sort of aperture-priority mode).

A lenses - all metering modes works and also the auto-exposure modes (except for the picture modes), but the lens has to be set to 'A' position. P-TTL flash doesn't work (needs a lens with distance info).

As for best lenses... Well, the optical formula is the same in many lenses...

A 50 f/2 is a good lens, but 50 f/1.7 and 50 f/1.4 are indeed better (they have same optics, so it doesn't matter if you go M, A, F or whatever...).

M 135 f/3.5 is a cheap and very nice 135. A 135 f/2.8 is harder to come by, but it is another good one. M 28 f/2.8 is nice, but not as nice as the (autofocus) FA 28 f/2.8 AL (I have both). The A 28 f/2.8 could be a winner.

In general, Pentax primes are excellent. Only some of the cheap zooms is best avoided.

Take care
R
 
Roland Mabo said:
A lenses - all metering modes works and also the auto-exposure
modes (except for the picture modes), but the lens has to be set to
'A' position. P-TTL flash doesn't work (needs a lens with distance
info).
Click to expand...
I have a DS and several A lenses, all of which work perfectly in P-TTL mode with the popup flash (which is P-TTL only on the DS).

I just re-confirmed this - I can see the preflash in the finder before the mirror lifts and exposure is correct. The lenses behave exactly like my FA lens except for AF, and of course no lens information is available in the EXIF - including distance.

--
John Bean

PAW 2005 Week 34:



See: http://waterfoot.smugmug.com/paw
 
I must test my A lenses, I haven't done it but you're probably right.

But I have my doubts that the results will be as good - because the multisegment metering uses distance info and A lenses doesn't have it, it must be some reason for it to use it and if the results are the same why use it at all?

Take care
  • R
 
Roland Mabo said:
Program mode, aperture priority and
shutter priority modes are not supported
Click to expand...
Actually you have sort of a very limited aperture priority mode with the Non-A lenses - if you use them with the aperture fully open (and only then).

IMO that can be useful sometimes - e.g. I have a quite usable manual 135/2.8 Ricoh lens which is sharp enough wide open, and I have successfully used it in low light situations with this "mini" aperture priority mode.

Phil
 
I've wondered about it myself and but I can see that subject distance is very useful if for example you have something in the foreground that's very reflective and your primary subject is further away; in this situation the matrix meter can make a very good guess that the brightly lit area is probably closer than the focused subject and should have less prominence than the darker area that is (probably) behind it. But lack of distance info is no reason to preclude P-TTL; the pre-flash serves to calibrate the flashgun output - just like using a flash meter - whereas the distance info simply fine-tunes the flash output as a result of the matrix metering of the pre-flash having extra information available.

"A" lenses work in "scene" modes as well, probably for similar reasons. I usually advise people that "A" lenses will work in all modes just like FA or DA lenses but (obviously) without AF.

--
John Bean

PAW 2005 Week 34:



See: http://waterfoot.smugmug.com/paw
 
63megapixel said:
What are the nice lenses (BOTH AF and MF) to start with (and cheap)
in Pentax system? For example, in Canon you can start with 50/1.8
28/2.8 and 135/2.8 for less than $200.
Click to expand...
That's pretty much the set you can easily find used for Pentax - the 50/1.7, anyhow. The 50 especially, as you have noticed, is plentiful and cheap, and by all accounts very good (I have it and like it, but have nothing to compare it to). The 28 & 135 are not in every pawn shop, but it shouldn't take too much hunting to find these, and you can indeed probably get all three all for under $200. It just might take a longer to complete the set.

Or, as I related recently in the thread called "LBA fixes on the cheap", you could see if any of your friends have old Pentax film cameras they no longer use since going to Canon or Nikon for their DSLR's, and get these even cheaper.

FWIW, I'm now having my doubts about the 28/2.8. Not that it isn't a fine lens. But given that my main reason for being interested in primes is low light photography, I'm not convinced the 28/2.8 buys me all that much over the kit lens. A full stop brighter at 28mm, sure, but only half a stop if I set the kit lens at 18, and if I'm shooting wide angle, chances are pretty good that 18 will work as well as 28.

--
Marc Sabatella
 
Yes, I believe that too. But A lenses and auto picture mode... It uses the distance info to discover a macro or a landscape shot. But manually selectable, well why not since the users has already told the camera by the picture mode what it wants.

For optimum performance of the metering, I still believe in a recommendation for autofocus lenses.

Take care
  • R
 
Well, the 28 f/2.8 becomes a good standard lens on the *ist D/DS/DL... It's definately sharper than the DA 18-55 at the wider aperture settings.
(Yes, even the "soft" M 28 f/2.8).

Take care
  • R
 
Roland Mabo said:
K and M lenses - spot and centrumweighted metering will work with
the camera in M)anual mode when you press the AE-L button (and if
aperture ring usage is turned ON in the Custom setting menu, please
refer to your manual, I don't have it nearby now).
Click to expand...
BTW, something that is usually not clear in descriptions of this process is that pressing AE-L in manual mode has no effect unless the meter is actually active. The meter can be turned on by either doing a DOF preview or half-pressing the shutter, and it remains on for a certain length of time that is controllable via a custom menu setting. It's obvious when the meter is on and when it isn't, so there is no guessing - if you see a display of metering info in the viewfinder, the meter is on. Also, you can hear the stopping-down action of the AE-L button if it's doing anything.

Implicit in this is something else that is not immediately obvious to everyone: if you stop a lens down using the aperture ring, this does not actually close the aperture immediately. It remains wide open until you do a DOF preview (in which case it stops down for the duration of the preview), or until you hit AE-L or fully depress the shutter (in either of these cases, the lens stops down only for a moment). This is presumably done so that your focusing is done with a wide open lens.

The bottom line is that in manual mode, it's basically a two-step process to set exposure with a manual lens - either a DOF preview or a half shutter press, followed by hitting AE-L.
Roland Mabo said:
Program mode, aperture priority and
shutter priority modes are not supported (but Manual mode with AE-L
button is actually a sort of aperture-priority mode).
Click to expand...
As Phil says, the aperture priority mode does works in one special way - it turns your lens into a fixed aperture lens (fixed wide open). And actually, program and shutter priority modes behave identically to aperture priority mode on these lenses. So you are get correctly exposed pictures every time in any of these modes even with fully manual lenses - you just have to live with maximum aperture. I guess most people don't consider that of much value, but considering my main reason for putting a prime on my camera is to get a wider aperture than my zooms can give me, it's actually not a bad little feature.

--
Marc Sabatella
 
Can you tell us what are the "cheap zooms (made by Pentax)" that should be avoided? I tried to get a 70-210mm zoom this morning but did not get it; it went over my max of $78. Thanks!
 
Roland Mabo said:
I must test my A lenses, I haven't done it but you're probably right.
Click to expand...
A lenses support P-TTL. I believe that if focal length and focus distance information is available, the DS takes advantage of it, but otherwise it defaults to integrating the metered ambient and flash illumination, sets exposure accordingly. Same for the difference between F and FA lenses: if MTF information is available, it might use that to additionally weight the choice of aperture and shutter speed, but in its absence uses a constant as default.
Roland Mabo said:
But I have my doubts that the results will be as good - because the
multisegment metering uses distance info and A lenses doesn't have
it, it must be some reason for it to use it and if the results are
the same why use it at all?
Click to expand...
The multisegment metering can use focal length, distance and MTF information, but without them it can still provide evaluative metering, just with those three parameter set to a constant. Just like linking AE and AF focus point can improve things, but isn't necessarily required.

Summary:
  • Pentax K-Bayonet and M series manual focus lenses without an A position on the aperture ring transmit no lens data to the camera body. Such lenses on the DS stop-down and allow semi-automatic metering in Manual exposure mode (using the AE-Lock button to trigger the meter operation when the meter is active) . Meter patterns are Spot and CW Averaging. Focus confirmation is provided using the center spot AF sensor.
They can be used in AE mode: all AE modes (program presets, auto picture, P, and Tv) default to Av priority, and the exposure is always made at wide-open aperture. The built-in flash when used with these lenses operates in non-metered, full output mode: set the aperture per the focus distance and ISO, set the shutter speed to anything below 1/180 sec.
  • set the custom function Using Aperture Ring to Permitted.
TTL flash metering is supported when using a Pentax-dedicated external flash unit.
  • Pentax A series manual focus lenses transmit maximum and set aperture to the body, and the body can control the aperture when they are set to the "A" position. All meter patterns and modes are available, focus indication works as above for K/M lenses. P-TTL flash works in all modes.
  • Pentax F and FA series autofocus lenses transmit more information to the body, including focal length (F, FA), focus distance (not sure), and MTF information (FA only). All functions of the body are supported with regards to AF, AE and flash metering. FA-J and DA lenses work just like FA lenses, but have no aperture control rings. D-FA lenses work exactly as FA lenses.
Any lens with an aperture control ring that includes the A position will work like a K/M bayonet lens if the aperture ring is set to any position other than A.

To be complete:
  • Pentax M42 screw mount lenses can be fitted using a thread to bayonet adapter. Such lenses can only be stopped down manually via an external, mechanical means if provided, or by modification of their auto-diaphragm mechanism. They must be stopped down manually for metering and exposure. Otherwise, they work just like K/M lenses. Focus confirmation like with the K/M lenses is supported, need to be turned on separately with a custom function.
Godfrey
 
Roland Mabo said:
Well, the 28 f/2.8 becomes a good standard lens on the *ist
D/DS/DL... It's definately sharper than the DA 18-55 at the wider
aperture settings.
Click to expand...
I suppose I should have made clear that I probably don't have the actual Pentax 28/2.8 - this one says "Gemini" on it and doesn't say "Pentax" (or "Asahi") anywhere. I wouldn't be surprised if Pentax didn't make something sharper, but this one certainly doesn't seem to be an improvement over the kit in that respect. My 135 is probably off-brand too, but it at least does comparable favorably with my cheap telephoto zoom at that focal length in temrs fo sharpness.

But then, I find both my zooms more than sharp enough even wide open. Again, it's not lack of sharpness that makes me interested in primes, but rather, low light performance. And I'm just finding that a 28/2.8 doesn't buy me all that much in this department. Even if it were a better 28/2.8 that produced sharper images wide open than the kit lens, I don't know that I would find this enough to making putting the 28/2.8 on worthwhile, because I still wouldn't be gaining much in terms of speed, and of course I lose quite a lot in terms of flexibility not being able to zoom.

Now, a cheap 28/ 2.0 would make me take notice. Although I am also finding that if I'm trying to shoot a scene with a focal length of 28mm, chances are pretty good it's not just one small subject I am shooting - it's a group of people, a large building, or something of the sort. And the depth of field is shallow enough at 2.8 that it's tough to get everything in focus. So even with the better low light performance, I'm not sure I'd really be able to take full advantage of a 28/2.0 very often, either.

Now, my 50/1.7 and my 135/2.8 I am finding quite useful, because these are lenses I'm generally using to isolate one subject. Limited depth of field is therefore often a plus. I like the 50 for that reason even when not shooting in low light, although I then often do close down the aperture a little .

Anyhow, I know this is all old hat to people who have been shooting SLR's a long time, but I'm just getting back into it after only a brief foray decades ago. So don't mind me if I think aloud sometimes.

--
Marc Sabatella
 
Why do you say that K mount lenses transmit no aperture value to the camera ?. I have an old Chinon CE4, an aperture priority SLR from about 1980. Its lens has no A position. The camera metered in wide open mode and so it must know what the aperture ring was set to so it could indicate and set the shutter speed prior to taking the picture. I am thinking of buying an *ist DL and assume that the Chinon lens (50mm f1.7) would also work on the *ist DL in aperture priority mode ?

I also have a Vivitar 28-205 (KA ?) zoom with an A setting on the aperture ring. I assume this will be OK for shutter priority mode on the *ist DL ?
 
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