green button

*Fl_Gulfer* · 08-07-2008, 10:45 AM

I just conected a SMC-A* 300 f4 to my K20D and took a few shots and noticed when I hit the green button nothing happens, I thought it was suppose to make a few adjustments like it does with my other manual lenses. I have it set on "A" and the camera on manual also tryed it on Av. Is there something I'm missing?
It's a very sunny day and if i shoot at something in the shade it's very under exposed and in the sun it's over. I know I still haven't learned how to use the lens yet since I just got it a hour ago.

Thanks Guys
Jack

deejjjaaaa · 08-07-2008, 11:02 AM

your signature says "PENTAX SMC-A* 300mm f1.4" - man, you will make some people VERY, VERY JEALOUS

Gooshin · 08-07-2008, 11:07 AM

Originally Posted by Fl_Gulfer

I just conected a SMC-A* 300 f4 to my K20D and took a few shots and noticed when I hit the green button nothing happens, I thought it was suppose to make a few adjustments like it does with my other manual lenses. I have it set on "A" and the camera on manual also tryed it on Av. Is there something I'm missing?
It's a very sunny day and if i shoot at something in the shade it's very under exposed and in the sun it's over. I know I still haven't learned how to use the lens yet since I just got it a hour ago.

Thanks Guys
Jack

if a lens has the "A" setting there is no need for the green button

the green button is for step down metering for those lenses that lack any electric contacts, therefore the camera is clueless as to what the aperture is, so you press the button, the camera steps down, meters, and sets the shutter speed.

when you put the lens in "A" mode, you can use any of the cameras modes, Av, Tv, ATv etc etc without pressing any additonal buttons

yes, it really is that simple.

*janosh* · 08-07-2008, 11:15 AM

Same sort of question, K20D and "M" lens...green button doesn't seem to do anything other than (evidently) DOF preview.. I thought it was supposed to meter?

How do you meter with an M lens (85/2) ? M? Av? User?

Gooshin · 08-07-2008, 11:16 AM

Originally Posted by janosh

Same sort of question, K20D and "M" lens...green button doesn't seem to do anything other than (evidently) DOF preview.. I thought it was supposed to meter?

How do you meter with an M lens (85/2) ? M? Av? User?

non contact lenses

you put the camera into M mode

you spin the aperture ring to select the aperture

then you hit the green button, it "steps down" (to your selected aperture) and meters, selecting the proper shutter speed.

*janosh* · 08-07-2008, 11:36 AM

Originally Posted by Gooshin

non contact lenses

you put the camera into M mode

you spin the aperture ring to select the aperture

then you hit the green button, it "steps down" (to your selected aperture) and meters, selecting the proper shutter speed.

Do you mean it's necessary to hold the green button down while exposing?

Sounds like a hand-held meter, or eyeball/experience, or chimping would be just as effective.... yes? no?

Gooshin · 08-07-2008, 11:44 AM

Originally Posted by janosh

Do you mean it's necessary to hold the green button down while exposing?

Sounds like a hand-held meter, or eyeball/experience, or chimping would be just as effective.... yes? no?

no you just have to press it once, it looks like its just a DOF preview but it actualy meteres

comprende?

*janosh* · 08-07-2008, 11:57 AM

comprende?[/size][/quote]

No..no comprende!

Does it remember this metering for following exposure/s or just give info?

Gooshin · 08-07-2008, 12:01 PM

Originally Posted by janosh

No..no comprende!

Does it remember this metering for following exposure/s or just give info?

it doesnt remember anything

when you are in manual mode, the camera will stay at whatever settings you told it to be at

so if the dial reads Av 2.8 and Tv 400

you can spin the camera from darkness into light these figures will not change

if you are using an M lens then you dont even have the option to select the aperture, all you can change is the shutter speed.

when you press the green button it will meter only what the camera is currently looking at

and it will not change its setting until you press the button again, or until you twist the shutter dial.

silent_eyes · 08-07-2008, 12:20 PM

Originally Posted by Fl_Gulfer

I just conected a SMC-A* 300 f4 to my K20D and took a few shots and noticed when I hit the green button nothing happens, I thought it was suppose to make a few adjustments like it does with my other manual lenses. I have it set on "A" and the camera on manual also tryed it on Av. Is there something I'm missing?
It's a very sunny day and if i shoot at something in the shade it's very under exposed and in the sun it's over. I know I still haven't learned how to use the lens yet since I just got it a hour ago.

Thanks Guys
Jack

K10d has option to set different functions to green button, so I suppose k20d does too, maybe it's just not set to do anything but dof preview, which is actually nothing if using manual lens... I guess you can change function to auto-adjust exposure or aparture when pressed, or something

Ben_Edict · 08-07-2008, 01:12 PM

Originally Posted by janosh

comprende?[/size]

No..no comprende!

Does it remember this metering for following exposure/s or just give info?

It "remembers" - simply because you have to work in M = MANUAL mode to do this. With the Green Button the camera selcts the appropriate shutter time and this is then fixed, until you9 change it yourself. Remember, it is the manual mode - the camera will only change the shutter speed, when you turn the dial or push the Green Button again.

It is a kind of "semi-automatic with exposure lock".

Ben

stevebrot · 08-07-2008, 01:35 PM

Ummm...let me get this straight

"A" lens
Aperture LOCKED at A setting
Green button does nothing in Av or M

The expected behavior is this:

In Av: Nothing should happen when you press the green button, but exposure should be OK.

In M: Again, the green button does nothing, correct exposure depends on adjusting shutterspeed/f-stop until the viewfinder display indicates correct exposure.

To rule out issues with the aperture stop-down, take the lens off the camera and rotate the aperture ring manually. The iris should change with each click stop. Check both extremes small/large. At the smallest aperture, make sure that flicking the actuator lever opens/closes the iris with no sticking.

There are more extensive tests you can do with the lens on the camera to confirm proper stop-down, but the instructions would be very long and I am short of time!

Steve

Shashinki · 08-07-2008, 01:39 PM

This thread is the reason why Pentax cameras come with this here interesting thing called "user manual".

To use it, you have to use a skill called "reading", so you might want to save up some experience points on your next level up.

Shashinki · 08-07-2008, 01:43 PM

I guess my "sarcasm" skill level isn't very high..

Marc Sabatella · 08-07-2008, 01:47 PM

[quote=stevebrot;311455]Ummm...let me get this straight

"A" lens
Aperture LOCKED at A setting
Green button does nothing in Av or M

Not true. Have you tried it in M mode? It works the same with "A" lenses as with FA or DA. Which is to say, depending on which camera and how you have it configured in the custom menu, the Green button in M mode will either set both aperture and shutter speed to whatever the "program" mode would have selected, or else it will keep the currently selected aperture and adjust shutter speed to give a proper exposure, or else it will keep currently selected shutter speed and adjust aperture to match. I have mine set to keep aperture and adjust shutter speed, because that's what's going to do anyhow with M lenses.

Of course, when using the aperture ring to set aperture, the camera has to stop down momentarily to take a meter reading, so you can *hear* it adjust shutter speed. Whereas with "A" lenses (and FA and DA), the operation is silent.