Pentax Green Button Guide

A look at one of Pentax's secrets

By johnhilvert in Articles and Tips on Aug 15, 2016

Note how the green button carries no label

John Hilvert delves into the charms of the misunderstood "green button" on Pentax cameras.

It may not change your life. Yet with just one press it can reset your camera's exposure back to defaults, offer you a dandy spot meter for non-automatic lenses, support you when using manual mode, speed up settings adjustments in the menu, and a lot more!

Not to be confused with Pentax's point-and-shoot green mode, the green button debuted in 2001 on the last Pentax film SLR, the MZ-S.  It followed on the very first Pentax DSLR, the *ist D, two years later. Described as a “Program Reset button” it could be applied quickly with just one press, depending on the mode and configuration of your camera.

On today's cameras, the button is found either on top near the shutter button, or to the right of the rear LCD.

So-called program reset buttons appeared on early electronic film-based SLRs such as the Yashica 230-AF (c. 1987) as a white button to protect against strong static electricity that could freeze its electronic controls. That button effectively re-booted its system so it could take pictures again.

It also appeared in the Minolta Maxxum 5xi/9xi  series in the late 80s offering a program reset button or “panic button” – which effectively returned almost all camera functions to normal. A variant was introduced with Nikon cameras to reset everything to factory settings by holding the bracket and metering buttons down together, for more than two seconds.

Pentax offered an early version of "green button" functionality when the company introduced the Hyper Program and Hyper Manual modes on the PZ-1 line of film cameras (more details on these modes follow) in the mid 90's.

However, today's green button makes a Pentax camera even more convenient. It requires little to no setup, but its versatility and inadequate description in many Pentax manuals undersold its utility and magic.

For example, my Pentax K-3 manual states "the green button resets the values being adjusted. Switches to ISO AUTO when adjusting the sensitivity." – which is very simplified. Later on, it implies you have to set up e-dial programming in five steps to make the green button work. This is also misleading and may be one reason many users don't touch the button after that.

Only when I read a fuller explanation in Yvon Bourque's K-3 ebook guide as well as the dispersed tips on, did I grasp what a gem green button can be— an all-purpose reset button which can instantly put your camera into a safe setting when you are unsure about what to do next.

The use of the green button also depends on the Pentax model you have.  There are various Pentax bridge cameras that offer a green button as well.

One of the first attempts to document the powers of the green appeared on Pentax Forums back in 2009 by PF member vizjerei. His thread is packed with detail and discussion, promoting thus button's magic and continued for five years after it began.

This guide offers a glimpse of some uses of the green button as well as a pointer toward its more advanced uses. You are not a Pentaxian unless you know at least three different uses for the green button, as it can be as useful as the back-button auto-focus button!

1. Reverting to the Recommended Exposure

The primary and most iconic function of the green button is simply to reset the exposure parameters (shutter speed and/or aperture, and possibly ISO) to those recommended by the camera. This function is the default in P, M, and TAv mode and generally applies only in these modes.  Thus, if you've made adjustments to exposure using the e-dial(s), the green button will reset those adjustments and use the values the camera thinks are optimal.  Plain and simple!

Whether the shutter speed, aperture, or ISO is adjusted will depend on your shooting mode and the parameters that you've customized manually.

In a sense, you could call this the "panic button", but in reality, it's more of a quick shortcut as it saves the photographer from having to turn the e-dials to get back to the camera's original settings.  It also gives you access to exposure automation while otherwise in a manual or semi-automatic mode.

In green auto mode (on the mode dial), the green button has no effect since the user can't influence the exposure.

What Recommended Settings?

How does the camera determine the combination of shutter speed and aperture that will be used?  The camera's auto exposure system follows what's called a "program line", which maps a combination of shutter speed and aperture settings to any given amount of ambient light (also called Exposure Value, or EV) as measured by the light meter. 

To put things in perspective, an EV of 12-15 would correspond to a daytime scene, while typical indoor lighting might have an EV of 5-7.

The exposure chart below contains two sample program lines (in green).  For the sake of simplicity, the ISO is not included, but also gets adjusted in practice where the lines are horizontal.

Sample program lines (green), by Darkekk2, CC-BY-SA 3.0

On the Pentax flagship series (645D/Z, K-1, K-3, K-5, K-7, K20D, K10D, *ist D), you can customize the program line to prioritize faster shutter speed (action), narrower apertures (depth of field), wider apertures (bokeh), or the sharpest aperture (MTF).  There's also a balanced "normal" setting which is the default, and is used on all cameras that do not offer program line customization.  Newer cameras have an "auto" setting that attempts to analyze the scene and pick most the appropriate program line.  We do not recommend this for advanced users.

Whichever program line you select will be used throughout all the primary shooting modes (P, Tv, Av, M, Sv, and TAv).

Selecting the program line via the main menu

Looking back at the chart, the green line on top might correspond to the depth of field program line, while the line below it might correspond to the normal program line.

Entry-level/mid-range cameras such as the K-70, K-50, K-30, K-01, K-r, K-x, K200D, K100D, or *ist DS only provide access to the alternate program lines through Scene Modes, which don't otherwise let you change the shutter speed or aperture.

E-dial Customization

Pentax cameras with two e-dials allow the user to customize the role of the dials and green button via the main menu.  The available choices will depend on the shooting mode.  Whenever "→P" or "P LINE" is shown, the green button has the function of reverting the shutter speed and aperture to the recommended values, as we've discussed.

Pentax K-1 Screenshot

E-dial and green button customization of the Pentax K-1

In M mode, there is also a "Tv Shift" and "Av Shift" customization option for the green button.  Tv Shift means the green button will only affect the shutter speed, while Av Shift means the green button will only affect the aperture value, respecting the user's choice for the opposite parameter.  On cameras with just a single e-dial, a separate option is available for this.  Other camers have it in the e-dial programming sub-menu.  These two options add a great deal of versatiltiy to the M mode.

Additional options on the Pentax K-01, K-30, K-500, K-50, and K-S1

Other possibilities for the green button include "--" or "ISO Auto", in which case the button has no function, or simply sets the ISO to automatic, respectively.

If you have the guide display enabled, the camera will show the current role of the green button every time you change the mode using the mode dial:

Guide display shows the role of the green button

So what's the difference between P LINE and →P as far as the green button is concerned?  None, outside of P mode.  In P mode, these terms refer to different sub-modes with different e-dial roles, and consequently a different state of the shutter speed and aperture.  In P mode, when →P is selected, the user has direct control over either the shutter speed or the aperture using the e-dials.  This is known as Hyper Program.  When P LINE is selected, user input would "shift" the program line in one direction or the other without explicitly specifying the shutter speed or aperture.  This mode is known as P Shift.  The function of the green button is the same in both cases: in undoes your customizations and returns you to plain old P mode.

Some might argue that the presence of Hyper Program along with the green button renders the Tv and Av modes redundant.


Suppose you had the camera in P mode and wanted to customize the shutter speed or aperture (i.e. utilizing Hyper Program).  After turning the corresponding e-dial, your screen would look something like this:

When the green button is pressed, the camera changes both the shutter speed and aperture to the values it would have used if no user input had been given earlier:

P mode after the green button

Now, for a second example. In M mode, suppose you dial in a combination of settings that resulted in underexposure:

M mode with underexposure

A press of the green button would bring the exposure back to 0.  Notice how the shutter speed and aperture are the same as in P mode— the camera follows the same program line regardless of mode.  Pentax calls the combination of M mode and the green button Hyper Manual, and it really is quite useful, as you always have the program line to fall back on as a starting point.

M mode after the green button

Finally, suppose you were in TAv mode and went with a combination of settings that necessitated a high ISO.  Note that TAv is in essence the same as M mode with auto ISO.

TAv mode before green button

The camera's program line calls for a wider aperture and much lower ISO, and this is applied at the push of the green button:

TAv mode after green button

These examples are from the Pentax K-1 but should apply to all other Pentax models since 2013.  Note that the green button doesn't have an effect in Tv or Av mode, though it theoretically could.

2. Stop Down Metering with Manual Lenses

Another key use of the green button is to allow proper metering with an M, K, or M42 (screw mount) lens.  In manual mode when the green button is pressed, the lens aperture will close and the internal light meter will then take a reading.  The camera then picks an appropriate shutter speed for the aperture selected on the aperture ring.

In a nutshell, all you have to do is press the green button before taking your picture, and the exposure should often be correct.  Ultimately, the green button does exactly what it would with an automatic lens, with the addition of the mechanical stop-down step.

For more details on metering with manual lenses, check out our step by step tutorial or watch the video below:

3. Reset Exposure Compensation, Flash Compensation

If you have set exposure compensation, hold the exposure compensation button plus the green button and it will reset the meter to zero exposure compensation. You can also reset the flash compensation while in the flash menu.

Newer cameras also allow you to press the green button shortly after pressing the exposure compensation button.

The green button resets the exposure compensation to 0
while the exposure compensation button is held down

4. Fast Access to Set Auto ISO

When you press the ISO button (OK button on K10D/K20D) and the green button at the same time, the ISO will bet set to auto. In Av or Tv mode, if the ISO is made accessible via one of the control dial, the green button switches to auto-ISO.

This only applies to the K10D, K20D, and subsequent cameras that have an ISO button.  Cameras such as the K-50 require you to enter the menu to enable auto ISO.

Note that M mode with auto ISO is displayed as TAv on cameras that do not have the TAv setting on the mode dial.

5. Resetting Menu Settings

The green button can be used in a variety of menu contexts, and it will generally reset a setting to its default value.  To name a few:

  • live view zoom
  • live view AF area position
  • Custom Image settings
  • bracketing range
  • white balance hue

An icon on the screen will show the function of the green button.

Unrelated to the green button, did you know that if an image is magnified in playback mode, the exposure compensation button zooms out by one step?  On older models, the green button zooms the image in, while on newer models, the e-dial is exclusively used for this purpose.

6. Video Mode

In video mode, the green button operates just like in a stills mode.  It will revert the exposure to what the camera recommends.

Live view before GBLive view after GB pressed
Before and after green button is pressed in video mode

7. The Green Button Does Nothing

There are some instances in which the green button has no effect.  To name a few:

  • You are in the Green/Auto Mode. This mode takes over everything and you have to accept what the camera decides. Pressing the GB does nothing in this mode.
  • You are in a Scene Mode that does not allow exposure customization
  • You the green button is set to do nothing under e-dial programming
  • You have not set an automatic lens to "A" on the aperture ring


The green button is a unique part of the Pentax user interface that adds a considerable amount of versatility in a number of shooting scenarios.  Next time you're in the menu, be on the lookout for tooltips telling you what the button does.  Also, take it for a spin in P or M mode!  Combined with Hyper Program and Hyper Manual, the green button can be a real time saver, if not a game changer!  It's suitable for use by professionals and beginners alike.

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