[jocko_nc]

What is the big deal with the A or FA with regards to auto aperture?

I have mostly M series lenses, but still have a couple of A's. When using the A lenses, I do not use the A function. I know how the auto aperture works, I just don't see much value:

You know whether you are shooting dark or light. Given the lens, that is the primary issue. The former, you stop it down a little. The latter, you know you will open the lens up. Av mode. Give a peek. The camera gives you a shutter speed that should work, if it looks reasonable take a shot. If you want to try some variations, switch to M mode and bump the shutter speed +/- 1 step.

Am I doing this caveman-style? Seems real easy to get exactly what you want.

"A" on the lens is really a good thing IMO. It is also very helpful with flash...

You can 'old school' it like an M lens if you want. I have a lot of m lenses, but all things equal I will shoot with an A if I can...

But to each his or her own
Primal Gus

[Venturi]

The top ten reasons for using (F)A lenses according to the home office in Scottsdale, AZ are:

10. The meter display goes dark.
9. The metering system likes a wide open aperture.
8. You lose Grn, P, Tv, Sv & TAv exposure modes.
7. Counting clicks sucks when there's a perfectly good LED display in the viewfinder.
6. The built-in flash I never use sticks out so far you can't see the numbers.
5. e-dials are koool!
4. Buying old M-series lenses on fleabay does not improve the Hoya/Pentax bottom line.
3. "F--" makes Baby Jesus cry.
2. All the really good M lenses are already owned by somebody else.

And #1 reason is...

1. What's an aperture ring?

[Class A]

The top ten reasons for using (F)A lenses according to the home office in Scottsdale, AZ are:

That's what I call edutainment!

[deuces]

Here's one you missed. Lens info in exif.

[egordon99]

Yeah, really NO reason to NOT use the 'A' setting if it's there.

About the ONLY esoteric reason I can think of is if you have a *ist D/DS and a Sigma EF-500 Super flash, you can force the flash to use TTL instead of P-TTL metering

[Lowell Goudge]

What is the big deal with the A or FA with regards to auto aperture?

I have mostly M series lenses, but still have a couple of A's. When using the A lenses, I do not use the A function. I know how the auto aperture works, I just don't see much value:

You know whether you are shooting dark or light. Given the lens, that is the primary issue. The former, you stop it down a little. The latter, you know you will open the lens up. Av mode. Give a peek. The camera gives you a shutter speed that should work, if it looks reasonable take a shot. If you want to try some variations, switch to M mode and bump the shutter speed +/- 1 step.

Am I doing this caveman-style? Seems real easy to get exactly what you want.

The only advantages of an A lens over an M or K lens are the following:

- A lenses can shoot in all exposure modes on a DSLR, K&M lenses can shoot apature priority wide open only, or manual mode using manual metering
- A lenses can be used with P-TTL flash, K&M lenses can only be used with Manual flash, auto flash (using flashes own sensor) or TTL (limited to *istD and DS)
- A lenses when used on a K10D or K20D meter better when in A then when using the apature ring, due to an apparent issue with scatter of light from the focusing screen inducing under exposure at large apatures <F2.8 and over exposure in at small apatures >F8

Except for these 3 things, there is no difference but unless you have an *istD to use with the K&M lenses you can be pretty frustrated with the K10D and K20D.

[Marc Sabatella]

I have mostly M series lenses, but still have a couple of A's. When using the A lenses, I do not use the A function. I know how the auto aperture works, I just don't see much value:

You know whether you are shooting dark or light. Given the lens, that is the primary issue. The former, you stop it down a little. The latter, you know you will open the lens up. Av mode. Give a peek. The camera gives you a shutter speed that should work, if it looks reasonable take a shot. If you want to try some variations, switch to M mode and bump the shutter speed +/- 1 step.

Um, it sounds like you are under the mistaken notion that Av mode actually *works* when using M lenses, or A lenses with the aperture ring not in the A position. It doesn't. The camera takes a picture, sure, and it's decently exposed, sure. But the aperture ring setting is completely ignored. It's shooting wide open (and setting shutter speed accordingly) regardless of the aperture ring setting.

So you say you don't much value in auto aperture, but what you are describing - using Av mode - in fact only works with auto aperture.

Now, I might agree this isn't such a big deal - I use M mode even with my A (and DA) lenses. But it is kind of a drag that with M lenses, or when the aperture ring is off "A", the meter display isn't active - you have to hold the DOF preview open to see the meter. Hitting the green button sets a shutter speed, and I can adjust from there, but it is nice to also be able to scan about to see what the meter says abut the light versus dark areas of the scene. So I use DOF preview a *lot* with my M lenses.

[stevebrot]

Ummmm...not wanting to sound too picky, but the term "auto aperture" has nothing to do with the "A" setting on the aperture ring of some K-mount lenses.

Auto aperture means that the aperture stays open until the time of exposure as opposed to manual aperture where it is always at the set opening or pre-set aperture where it may be set in advance and stopped down manually with a special lever or ring. All auto aperture lenses have a coupling mechanism that stops the lens down just prior to exposure. On M42 auto lenses this is a small pin on the mount. On K-mount lenses it is a lever.

As for The "A" setting...when present, it means that the lens supports setting the aperture from the camera body such as for programmed and shutter-priority exposure automation.

Steve

(Always preferring precision of terms when dealing with technical issues...)

[Marc Sabatella]

Ummmm...not wanting to sound too picky, but the term "auto aperture" has nothing to do with the "A" setting on the aperture ring of some K-mount lenses.

True, the correct term for what the "A" setting allows for is auto *exposure".

[creampuff]

One of the reasons why I have dumped all my lenses older than the A series is simply because with a modern DSLR, I want the functionality to use ALL of the exposure modes available. Using M series lenses is just too limiting imo.

One other consideration is that with the A series lenses and older, you can only use the center AF point and not the other 10 focus points.