[Jonas B]

Question (maybe a dumb one): I have the Pentax 50mm 1.7 "M" lens and have always had trouble focusing it. I have never used the aperture ring on the lens (which goes from 1.7 to 22, as many of you know). Should I have been using the aperture instead of letting the K100D camera do it. Freddy

Hi Freddy,

Have a look at this thread about how to handle a manual lens:
Manual focusing and metering: Pentax SLR Talk Forum: Digital Photography Review

(What do you mean - "let the camera do it"? The camera can not set the aperture with an M lens. It has to be done with the aperture ring.)

--
Jonas

[Jonas B]

I-snip-
but can't you set your preferred F-stop with the ring and then the camera will automatically choose which shutter in the proper mode?

I know my old SLR did this....

randy

No you can't. The camera don't know what position the aperture ring is set to. Thos were the days before Pentax started to save every possible dollar by giving us the crippled K-mount cameras.

--
Jonas

[Jonas B]

Or, with the lens's aperture ring on A, will it work just like all the rest of my lenses automatically?

Yes it will. Just leave it there and everything will work the way you are used to from the DA lenses.

--
Jonas

[roy]

my thoughts about NOaperture ring. i think it's an abomination for a lens not to have one.. nuf said.
roy

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Last edited by roy; 02-11-2007 at 02:48 AM.

[mtngal]

With M or K lenses, if you have the camera set for anything but M mode, the camera will meter and operate, but won't control/stop down at all - you are shooting wide open. If your lens is sharp wide open and you are in dimmer light, it's nice because you don't have to remember to push the button to meter. However, if you are using a 1.4 lens in bright sunlight, or if your lens is soft wide open, then it can be a disadvantage.

[davemdsn]

I started out with a Pentax ME Super, using the aperture ring to set the lens aperture. Then I got the wonderful PZ-1P (awesome camera) which had the ability to set the lens aperture either at the lens or at the rear control wheel. I ended up using the control wheel on the camera after while, largely because the camera will maintain the same f-stop when you change lenses so you don't have to stop to think about what the lens you just put on is set to. When the MZ-S came out I was really excited to get back to setting the aperture on the lens (only option on that body). It turned out to be the thing I liked least about that camera. I am really glad the *istD and K10D operate more like that great old PZ-1P.

[SpecialK]

my thoughts about NOaperture ring. i thinks it's an abomination for a lens not to have one.. nuf said.
roy

I have 2 lenses with aperture rings. I use the lenses, but never use the aperture rings. It's set through the camera, [Shrug]

[chedoy]

I don't have an apeture ring on my sigma.... I really miss it....
but can't you set your preferred F-stop with the ring and then the camera will automatically choose which shutter in the proper mode?

The proper mode is Manual mode and it picks the correct shutter fpr your aperture setting only if you press the appropriate button on your camera to meter before the shot. That's almost automatic enough for me. It will keep that shutter speed so you could shoot w/o metering if the lighting is consistent.

If you have an automatic lens, like an FA or A series, going with the ring is throwing away capability. It only works in manual mode and now you have to press the meter button, an extra step.

In Av or Tv mode on a K100D, forcing the aperture setting via the ring on a FA lens or older M/A lens is moot. It will shoot wide open, but will meter automatically. So if you were going for bokeh, that might work for you.

It's different with screw mount lenses, Shoot them in Tv or Av mode and it uses whatever aperture set on the lens.

I am used to the aperture ring though. With manual lenses, setting the ring is OK and habit with me.

[egarrard]

It is there for the good old times sake

When these F and FA lenses were published, Pentax bodies had an coupler to connect the aperture ring to body. This coupling relayde the user set aperture information to body for exposure calculations. Time was set from body wheel and aperture was set from aperture ring. If you wanted that aperture was set automatically by body, you turned the ring to A. If you wated to set aperture youself, you turned the riong to this value. Bodies didnt have the aperture wheel yet.

Nowadays bodies dont have this coupler anymore but they have aperture wheel. In these new bodies we have now, you have to for automatic modes setting also the aperture or to set aperture manually, have the aperture ring to be set to A.

Shortly: in newer bodies it is historical relic. Newer lenses dont have it anymore.

And it is very sad that Pentax dropped the coupler. Some of us LIKE the aperture ring and wish the cameras still had full functionality with it. How much money did they save when they took the coupler out?

[carpents]

I set three variables with each shot: aperture, exposure compensation, and ISO.

Three dials on the camera isn't really feasable...wouldn't it be great to set the aperture with your left hand - on the lens?!

--Sean

(PS - Kudos to Pentax for the K10 firmware that moved ISO to the OK button + scroll wheel. I use it often.)

[NaClH2O]

Question (maybe a dumb one): I have the Pentax 50mm 1.7 "M" lens and have always had trouble focusing it. I have never used the aperture ring on the lens (which goes from 1.7 to 22, as many of you know). Should I have been using the aperture instead of letting the K100D camera do it. Freddy

Hi Freddy, No it's not a dumb question, but if you have a lens with an aperture ring and no "A" position, (ie M, K and SMC Pentax) lenses, the camera CANNOT set the aperture. It uses the lens in the wide open (in your case the 1.7 setting). This is not necessarily a bad thing, but on a bright sunny day there will be too much light, and in all circumstances you have no control over DOF. A smaller aperture (larger fstop number) would give a larger DOF which will certainly help your focusing, since more of your subject will be in focus. If you are still unsure what I'm talking about PM me and I'll try to respond in greater detail.
In addition, here is a wonderful set of exercises you can do to improve your focusing skills. I'm using them, and I've found them to be most helpful
Re: Is a KatzEye required for those using manual focus?: Pentax SLR Talk Forum: Digital Photography Review

NaCl(hope that helps)H2O

[MPrince]

Saltwater, if I understand what you are saying, then I think you are only partially correct, at least with respect to the K100D.

When using an M lens in a mode other than Manual, the camera operates in Av mode, even if the mode dial is set to Tv or P.

In that situation, what you say is correct--the aperture remains wide open regardless of the aperture ring setting.

However, in M mode, the aperture setting can be read by the camera.

Try this--set your aperture ring wide open, half-press the shutter button, then press the AE-L button. The shutter speed will be set.

Take a picture.

Now, stop down the lens to, say, f8, half-press the shutter button, then press the AE-L button. The shutter speed will change by the corresponding number of stops.

Take a picture.

You should see the difference in DOF. This tells me the camera is reading the aperture correctly when in M mode.

See page 188 of the K100D manual.

[GregNS]

My answer only relates to *IST-DS2/DS/D cameras that have the TTL sensor, but I have to add that I use the aperture ring all the time when shooting flash with my daughter in the picture.

It's been discussed to death elsewhere, but moving the aperture ring away from "A" forces the camera into TTL mode rather than P-TTL (if you have an external flash that can handle either).

I specifically look for lenses with the ring now.

[RiceHigh]

Full Answer Here: K Mount Metering & Exposure Bases - A Technical Brief

What's the point of the 'aperture ring' that people keep talking about? All I ever hear anybody say is 'put it on A'. What other options are there and why are they there, if A is the only option anybody would want to use.

Will

[egordon99]

Nope, 100% incorrect! There is NO mechanical coupling for the aperture level to be read by the camera body. The camera has NO idea what the aperture is set to.

What happens is you set the aperture ring to f/5.6 (as an example). You are in M-mode. The lens is wide open while focusing/composing. You hit the Green-button/AE-L button. The camera will "pretend" it's taking a picture (same thing that the DOF preview switch does) and stop the lens down to whatever aperture you selected on the ring (the same aperture you will use for exposure). As it does this, it takes a light reading for the exposure. It then sets a shutter speed based on this light reading and the ISO set.

Normally the meter calculates a shutter speed (in Av mode with an "A" lens) related to the aperture set, the light coming in (while the lens is wide open), and the ISO. By knowing what aperture you want, it can determine how many stops from wide open you want and calculate the appropriate shutter speed (ie you are using the FA 50mm f/1.4 it measures light coming in at f/1.4, but you want the shot to use f/2.8, it knows that there will be four times less light during the exposure)

But when the aperture ring is NOT set on A, it does not know (1)What the wide open aperture is and (2)What aperture you set on the ring. The meter can ONLY measure the light during the stopping down of the lens.

Just wanted to clarify this point.

However, in M mode, the aperture setting can be read by the camera.

Try this--set your aperture ring wide open, half-press the shutter button, then press the AE-L button. The shutter speed will be set.

Take a picture.

Now, stop down the lens to, say, f8, half-press the shutter button, then press the AE-L button. The shutter speed will change by the corresponding number of stops.

Take a picture.

You should see the difference in DOF. This tells me the camera is reading the aperture correctly when in M mode.

See page 188 of the K100D manual.