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12-01-2016, 02:07 PM   #1
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Older lenses on K3 Pentax A

Hi there,

I have several older lenses and just wanted to check, i think to make the camera meter correctly in aperture priority mode using the old lenses you would press the green button
is this correct?
and do i have to do this before every single picture / do i have to hoold down the green button whilst trying to press the shutter at the same time?

the lenses are auto aperture but manual focus (Pentax A) style lenses.

thanks
K

12-01-2016, 02:20 PM   #2
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If your lens has the aperture ring in the "A" setting and the lens is detected correctly then you should be able to simply meter and shoot without the green button in Av mode or TAv mode or even Tv mode. Some errors may creep in as the metering mode is not matrix and the lenses have larger inaccuracies in metering than DA lenses. Typically a little chimping is needed or shooting in raw to make adjustments to lighting.
12-01-2016, 02:26 PM   #3
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QuoteOriginally posted by UncleVanya Quote
If your lens has the aperture ring in the "A" setting and the lens is detected correctly then you should be able to simply meter and shoot without the green button in Av mode or TAv mode or even Tv mode. Some errors may creep in as the metering mode is not matrix and the lenses have larger inaccuracies in metering than DA lenses. Typically a little chimping is needed or shooting in raw to make adjustments to lighting.
ah ok then thanks, so the green button only really needed with the older K and manual lenses then
12-01-2016, 02:31 PM - 1 Like   #4
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QuoteOriginally posted by Kyrsten Stone Quote
ah ok then thanks, so the green button only really needed with the older K and manual lenses then
As far as I recall. I can't recall how M mode works with A series lenses but I think even then you are metering wide open and setting aperture on the camera using the A setting on the ring.

12-01-2016, 03:41 PM - 1 Like   #5
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The green button is also used in P mode to reset the exposure back to the program line.
12-01-2016, 04:43 PM   #6
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QuoteOriginally posted by UncleVanya Quote
I can't recall how M mode works with A series lenses but I think even then you are metering wide open and setting aperture on the camera using the A setting on the ring.
With my A 50mm shooting in M, as always, I set aperture on the camera with lens locked on the A. You don't need to use the Green Button for M or K lenses either if you know what you're doing and are shooting in M mode on the camera.
12-01-2016, 05:41 PM   #7
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Care to elaborate about K and M lenses, photolady?
12-01-2016, 05:55 PM   #8
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Hope I'm not butting in, but I think what photolady's getting at is that if you either (a) have a hand-held light-meter or (b) have enough experience of various lighting conditions to take an educated guess at the shutter speed, you need only set it, set the aperture on the ring, and shoot. The camera will stop down appropriately when you take the shot. (See also "Sunny Sixteen rule", and variations thereon).

Depending on how your options are set up, you can have an EV indication in the viewfinder telling you how close (or off) you are, and use that as well.

With a DA lens, the green button forces an emergency revert back to the correct shutter and aperture settings (as determined by the inbuilt meter and its algorithms), handy for when I am shooting slowly and deliberately in manual mode but suddenly a dog or one of the kids does something cute across the room and I need to reset values for a different value of lighting without hesitation, or I want the camera's suggestions but also the right to vary them immediately without it taking over. With a K or M lens, or third party equivalent, the camera body doesn't have knowledge of the actual aperture but the nice people at Ricoh (and Hoya and Pentax before them) arranged for it to stop the lens down to its current set value, check the incoming light, and assign the appropriate shutter speed. Yay!

The only reason I have found to use the actual ring on the A and FA series lenses I own is when I'm using either "dumb" extension tubes or a reversing ring and there is absolutely no connection between camera and lens aperture systems, or when I'm comparing lenses of identical focal lengths but different eras (e.g. Takumar vs. M vs. FA) and want to make absolutely sure they are set for the same apertures with no surprises in-camera.

12-01-2016, 06:00 PM   #9
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When I shoot I always use M mode so for M lenses I just select the aperture I want to use. For me it works and I don't have to use the green button. With the camera in M mode, it's like using a film camera like I learned on my K1000. This doesn't work if you use AV mode though.

I have never used a K lens to my knowledge on my dslr's so can't confirm that what I do works on them as well.

But if you want samples I can provide those as well.
12-01-2016, 06:02 PM   #10
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QuoteOriginally posted by pathdoc Quote
(b) have enough experience of various lighting conditions to take an educated guess at the shutter speed, you need only set it, set the aperture on the ring, and shoot. The camera will stop down appropriately when you take the shot. (See also "Sunny Sixteen rule", and variations thereon).
Exactly!!
12-01-2016, 07:43 PM   #11
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QuoteOriginally posted by Kyrsten Stone Quote
Hi there,

I have several older lenses and just wanted to check, i think to make the camera meter correctly in aperture priority mode using the old lenses you would press the green button
is this correct?
and do i have to do this before every single picture / do i have to hoold down the green button whilst trying to press the shutter at the same time?

the lenses are auto aperture but manual focus (Pentax A) style lenses.

thanks
K
A,M,K lens will use center spot light metering
"A" lens set in aperture priority automatically sets shutter speed at what you are pointing at just depress shutter.
"A" lens in M mode adjust your aperture and shutter via your dials
"K" & "M" lens will use center spot light metering
"K" & "M" lens will require set up in your menus to release the shutter when the aperture is set to something other than A, you will also need to use the optical preview feature to get the light meter setting in M mode as over or under and adjust your aperture at the lens and your shutter at the dial
The green button best used with "A" lens in M Mode to get the quick exposure numbers.
12-01-2016, 08:49 PM - 1 Like   #12
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A manual "A" lens set in the "A" mode should behave exposure-wise the same as FA/DA/DFA lenses. This includes matrix metering. The main operational difference is that there is no auto focus, you can only use the center focus point and you have to input a focal length for SR. Otherwise you can use all modes (P, Tv, Sv, Av, Tav,, etc.) and the eDials will operate same as they would as with auto focus lenses. M mode is the same - EV bar meter turns on with the half-press of shutter, adjust shutter speed and aperture with the eDials.
12-01-2016, 08:59 PM   #13
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QuoteOriginally posted by Not a Number Quote
A manual "A" lens set in the "A" mode should behave exposure-wise the same as FA/DA/DFA lenses. This includes matrix metering. The main operational difference is that there is no auto focus, you can only use the center focus point and you have to input a focal length for SR. Otherwise you can use all modes (P, Tv, Sv, Av, Tav,, etc.) and the eDials will operate same as they would as with auto focus lenses. M mode is the same - EV bar meter turns on with the half-press of shutter, adjust shutter speed and aperture with the eDials.
I always get this confused. So A series does permit Matrix - thanks.
12-01-2016, 09:15 PM   #14
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QuoteOriginally posted by UncleVanya Quote
I always get this confused. So A series does permit Matrix - thanks.
And P-TTL flash.
12-01-2016, 09:56 PM - 1 Like   #15
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If it is a K or M lens, focus, push and release the green button, press the shutter. If it is an A lens, set the lens to A and use AV mode if you like, and you can adjust aperture with the wheel.
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