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04-15-2016, 12:06 PM   #1
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Green button.

Hi peeps

I just got my first 'real' lens, the 50mm DA 1.8, prior to this i was using an old manual only lens the 50mm 1.7 SMC-A.

I have gotten very use to the manual lens and can no longer figure out how to use my new lens in relation to the Green Button (which by the way, what's its real name?, is it a light meter, zero exposure button?).

With the old lens I controlled the aperature via the ring, in a sense it was always fixed. When pressing the green button it would adjust ISO and shutter speed only (sometimes just shutter speed if ISO was also set to fixed. How can I make my new lens the DA 50mm 1.8 also keep the Aperture fixed when pressing the Green button and only adjust ISO and Shutter Speed? Which mode should I be in, I'm guessing not Manual for this (as Manual adjusts all 3)?

Also, if yer in Manual Mode, and before the shot you press the Green Button and then take the pic, how is this in anyway different than setting the K-50 to Auto mode and snapping the shot? In Auto mode is the Green Button kinda 'permanently' working for the user?

Cheers,

Bruce

04-15-2016, 12:09 PM   #2
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The green button's technical name is... ... Green Button!

Use your camera in Av mode and select the aperture with the E-dial, and the camera will adjust SS and ISO without the need to even press the green button, unless you set ISO manually.
04-15-2016, 12:12 PM   #3
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Woah! <goes to try that>

So it does, cool!

So if I set the ISO to be within a range, say 100-1600, I noticed it's value along with the shutter speed also change together. How does it compute what to do? Like... does it say "I'm gonna try and not drop below 60th sec shutter speed and adjust ISO accordingly" ie does it prioritise one thing a little more than the other?
04-15-2016, 12:14 PM   #4
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QuoteOriginally posted by BruceBanner Quote
Woah! <goes to try that>
It's just like using your A 50/1.7 when the aperture is set to A but it also has this mysterious thing called auto-focus. Any idea what that is?

04-15-2016, 12:22 PM   #5
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Bascially the green button resets exposure to the camera's program line. With a mechanical lens without electrical contacts for aperture readout by the camera, the green sets the time only because it can't set the aperture (and sets the ISO too if you have Auto ISO turned on) - and it measures the light to know the aperture because it can't read it from the electrical contacts since such a lens does not have them. With a DA lens it simply resets the exposure, and it can do this in both manual and program modes.

Now, depending on the camera, the green button can be configured in many ways. Exactly what options are available is dependent on the camera model. For example - On my K-x I can set the green button to act as depth-of-field preview if I want to...
04-15-2016, 12:24 PM   #6
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QuoteOriginally posted by BruceBanner Quote
So if I set the ISO to be within a range, say 100-1600, I noticed it's value along with the shutter speed also change together. How does it compute what to do? Like... does it say "I'm gonna try and not drop below 60th sec shutter speed and adjust ISO accordingly" ie does it prioritise one thing a little more than the other?
Not sure...
I rarely shoot outside of Av with manual ISO so I'm not sure of the logic.
04-15-2016, 12:54 PM   #7
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In Av mode the ISO is fixed, so you need to control that yourself directly. Set the aperture with the e-dial , when you half press the shutter the metering circuit comes to life and the camera chooses the shutter 'speed' . You can adjust the exposure time( therefore the brightness) with the 'exposure compensation' control (press button and turn e-dial ).
04-15-2016, 01:03 PM   #8
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QuoteOriginally posted by mcgregni Quote
In Av mode the ISO is fixed, so you need to control that yourself directly. Set the aperture with the e-dial , when you half press the shutter the metering circuit comes to life and the camera chooses the shutter 'speed' . You can adjust the exposure time( therefore the brightness) with the 'exposure compensation' control (press button and turn e-dial ).
Not sure this is correct, at least for me. I can set my ISO to being within a range, say 100-1600, and as I move my camera around the room pointing at different places both values (shutter speed and ISO) adjust together accordingly at the same time. ISO is only fixed if I make it fixed. Not even pressing the shutter button here, there already seems to be metering anyway regardless of shutter button. What am I missing here?

04-15-2016, 01:12 PM   #9
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Yep, you can set an auto iso range while in Av mode.
04-15-2016, 01:32 PM   #10
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QuoteOriginally posted by bertwert Quote
Yep, you can set an auto iso range while in Av mode.
Normally use the green button, not the shutter botten half-way with non-A-lenses (or not set to A)
A on the lens is 'automatic' so that the body can adjust the aperture on the lens.
This is oposed to the old style 'automatic stop-down' since the modern body doesn't come with stop-down feeler.
In an older (before MZ-7) body there is such a feeler and thus the pressing half-way does only measure but also closes the aperture to the set value. With the modern (digital ) body there is no feeler and the only way to let the body know there is an aperture to close, you need the green-button.

When you don't use it or use the 'automatic' function, you will be taking pictures with the aperture fully open (for example f/3.5 instead of f/11)
I normally use the 'manual' function in the body, press the green button and the right value comes out for the exposure and you can adjust it the way you want to.

By the way, don't forget to change the user-setting for the 'old lenses' (aperture ring not set to 'A') in the user-functions, otherways it will only use the lens in 'A'.

With the lens in 'A'mode with the new lens you can still to the same, just make it 'non A' again.
04-15-2016, 01:54 PM   #11
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With "A" lenses (in a mode if the lens has an aperture ring) the Green Button does different things depending on the mode. Usually it sets one or a combination of exposure settings, e.g. shutter speed, f-stop and/or ISO, in accordance to the program line settings. You would have to look at either the documentation or go through the custom settings menu for each mode and see what the green button can be set to. Or go through each mode and see what the green button does. The rear LCD may display what the green button is set to when you change modes.

With the SMC-A 50mm f/1.7 you can set it to "A" mode and use the eDial to set the f-stop.
04-15-2016, 02:22 PM   #12
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Depending on the Pentax DSLR, the "Green Button" might not be green, instead being labeled "AE-L." Allowing manual setting of the aperture in the Settings, is crucial if you want to use old manual lenses, especially those from before the time there was either an "A" or "AE" setting on the aperture ring.
04-15-2016, 02:26 PM   #13
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QuoteOriginally posted by elvinhaak Quote
Normally use the green button, not the shutter botten half-way with non-A-lenses (or not set to A)
A on the lens is 'automatic' so that the body can adjust the aperture on the lens.
This is oposed to the old style 'automatic stop-down' since the modern body doesn't come with stop-down feeler.
In an older (before MZ-7) body there is such a feeler and thus the pressing half-way does only measure but also closes the aperture to the set value. With the modern (digital ) body there is no feeler and the only way to let the body know there is an aperture to close, you need the green-button.

When you don't use it or use the 'automatic' function, you will be taking pictures with the aperture fully open (for example f/3.5 instead of f/11)
I normally use the 'manual' function in the body, press the green button and the right value comes out for the exposure and you can adjust it the way you want to.

By the way, don't forget to change the user-setting for the 'old lenses' (aperture ring not set to 'A') in the user-functions, otherways it will only use the lens in 'A'.

With the lens in 'A'mode with the new lens you can still to the same, just make it 'non A' again.
QuoteOriginally posted by Not a Number Quote
With "A" lenses (in a mode if the lens has an aperture ring) the Green Button does different things depending on the mode. Usually it sets one or a combination of exposure settings, e.g. shutter speed, f-stop and/or ISO, in accordance to the program line settings. You would have to look at either the documentation or go through the custom settings menu for each mode and see what the green button can be set to. Or go through each mode and see what the green button does. The rear LCD may display what the green button is set to when you change modes.

With the SMC-A 50mm f/1.7 you can set it to "A" mode and use the eDial to set the f-stop.
Ok... getting a bit lost here and showing my ignorance.

With the old manual 1.7 lens, in order to get it to work I had to go into menu options 4>22. Using Aperture Ring and set to '2' (this is on a K-50 by the way). Otherwise it didn't work at all. That's the only menu tinkering I did to get things up and running I think. Then I pretty much set to manual and used the green button to adjust the iso and shutter speed etc (as a starting point) and manually focus and change the aperture ring if I wanted to.
What you talk of with setting to 'A', is this perhaps the same as my menu '2' just in a different model of Pentax, or is this something else in the menu?

What is the 'f-stop'?
04-15-2016, 03:10 PM   #14
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I wonder if the auto -ISO functioning has changed then since the K7/K5? Certainly on these models it's only in Tav or green mode that the ISO would vary automatically..... I think I would find ISO AND exposure time changing in Av mode confusing. Have the later cameras added this, and can it be turned off in Av mode?
04-15-2016, 05:38 PM   #15
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QuoteOriginally posted by BruceBanner Quote
Ok... getting a bit lost here and showing my ignorance.

With the old manual 1.7 lens, in order to get it to work I had to go into menu options 4>22. Using Aperture Ring and set to '2' (this is on a K-50 by the way). Otherwise it didn't work at all. That's the only menu tinkering I did to get things up and running I think. Then I pretty much set to manual and used the green button to adjust the iso and shutter speed etc (as a starting point) and manually focus and change the aperture ring if I wanted to.
What you talk of with setting to 'A', is this perhaps the same as my menu '2' just in a different model of Pentax, or is this something else in the menu?

What is the 'f-stop'?
Hey Bruce, to answer the last question first, the f-stop is the same as aperture. When others were writing about the "A" setting they are referring to A type lenses which are the old manual film lenses with an A setting on the aperture ring (Congratulations on figuring out how to use legacy glass from the start BTW:-)). When they are placed on a digital camera and set to A you can control the aperture through the camera like your DA 50 lens. I think you do need to read your manual in order to get the most out of your camera. If you want an easier read I would refer you to Yvon Bourque's e-books on Pentax cameras: #ebooks4pentax. He goes through all the menu options and tells you what they're for. You may also want to do some brushing up on general photography as well. Brian Peterson's [U]Understanding Exposure[U] is a classic and very good read. I also found Digital Photography for Dummies very helpful when I was starting out. As to the question of the auto ISO parameters, I don't know if the K50 has it or not, but, on the K3 there is a menu setting that lets you control this. It gives three settings: slow,medium and fast. As for the Green Button, It has many functions, mainly as a kind of reset/zero setting, but, can be programed depending on mode.

PS. I just noticed that you said in your post that you have an SMC A 50/1.7. If that is the case you should be able to set the aperture ring to A and you don't need to bother with the green button to determine exposure and you should be able to use any mode. Give it a try:-).

Last edited by sundr; 04-15-2016 at 05:53 PM.
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