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Tuesday, January 16, 2007

Easter Egg Number Two: Pentax's Green Button

by Carl Weese

The Green Button, like Digital Preview discussed last time, won’t be new to long-time Pentax users, but it’s an interesting feature that addresses a larger issue that might not seem immediately apparent. The Green Button sits next to the shutter release on the K10D, and it performs different functions depending on which mode the camera is in. What I want to talk about is the way it functions in “Hyper Manual.”

First, a little background. 35mm cameras from the first Leica onwards have offered a shutter speed dial located near the shutter release, and an aperture ring on the lens. I grew up with this set of controls, starting with the first serious camera I bought back in 1964 (instead of using my Dad’s Speed Graphic and Rolliecord)—a Pentax H3. I moved on to M-Leica and Nikon cameras (F2, F3, F4). When automatic exposure came in with the F3 I experimented with it but found I preferred to stay with manual exposure. Same with the F4. My most recent Leicas are M6s which have a meter, but no automation, which is fine with me. With the “analog controls” of shutter dial and aperture ring, you can keep a tactile connection to the settings as you wander around, constantly adjusting for ambient light conditions almost as a reflex, often without even looking at the camera. Your hands learn how to open up two stops as you move from sun to shade. I wrote about this in an article for Photo Techniques magazine called “The Leica Mystique” back in 1995 that you can still get as a back issue.

When I first got a good DSLR camera, in 2004, I quickly found that manual exposure had become completely non-intuitive. The control was there, at least in theory, but you had to use two blank, unmarked control wheels that have no endpoints to their travel. The only way to know what you’ve adjusted is to look at tiny digital readouts of speed and f-stop on the top plate LCD or in the finder. It just isn’t the same. In fact, as far as I’m concerned, it just doesn’t work—except for controlled situations like studio lighting or tripod shooting. I decided I would have to learn to work in automatic modes, usually aperture priority or full program, with the camera’s custom menu set so that I could override the automatic exposure just by moving a control wheel, without having to hold down a second button.

After a few thousand exposures and analysis of them, I got pretty good at guessing when the camera would need to have exposure compensation dialed in with the front control wheel, or when the program should be shifted to favor fast shutter or deeper depth of field with the rear control wheel. I still missed manual exposure, though. In a situation with a long tonal range, if you want to make a number of slight variations in framing, using auto-with-override is a real pain because you may have to change the amount of override each time you tweak the framing.

The Naugatuck River, Waterbury, Connecticut, 1/14/07

(If the camera is set in any mode of automatic exposure, a different amount of override will be needed for even the slightest change in framing a picture like this. Here, –2/3 stop worked. But it would be easier to set a manual exposure that just holds the sky values. Then the framing could be changed at will without bothering about the exposure.)

Increasing a bright sky area from 15% of the frame to 20% can require 2/3 stop change in the override. If the camera had been set to a correct manual exposure in the first place (the most exposure that retains tone in the sky), you could change the framing all over and keep shooting at that correct exposure.

This is where the Green Button comes in. With the K10D in manual, it works as awkwardly as any other dual-control-wheel DSLR manual exposure system, until you invoke the magic green button. If you point at a possible picture and hit the Green Button, the camera momentarily reverts to Program mode and sets the shutter and f-stop as it would in program. Then it lets go and you have full control with the rear wheel running the f/stop and the front wheel running the shutter speed. (For some reason this is still counter-intuitive to me, though the Olympus E-1 I’ve used for several years also sets the wheels this way in manual. If I had my way I’d have the front wheel do the aperture and the rear wheel do the shutter.) Now, instead of overriding auto exposure for a particular framing, you dial in some up and down marks on the in-finder exposure scale to set an absolute exposure for this particular scene. If there’s time, use the Digital Previw to get RGB histograms to review, tweak as needed, then go ahead and shoot any framing changes you want without constantly fiddling to compensate for whatever error the automation would introduce with each new framing.

This is seriously cool. I don’t think it’s as good a manual system as classic shutter speed and f-stop controls, but it’s a really imaginative workaround that I’m finding quite useful.

Posted by: CARL WEESE

Carl's Pentax K10D Thought Process to Date:
Part I: "On Buying a Camera"
Part II: "Less is More"
Part III: "On Testing a New (Digital) Camera, Steps A and B"
Part IV: "Weese on Anti-Shake"
Part V: "Anti-Shake Pt. II, or, Shake Reduction as Virtual Tripod for Nature Work"
Part VI: "The Camera-Manual Easter Egg Hunt: Pentax Digital Preview"
Part VII: "To Delete or Not, That is the Question..."


Blogger Olaf Ulrich said...

Carl wrote:
> ... the rear wheel running the
> f-stop and the front wheel running
> the shutter speed. (For some reason
> this is still counter-intuitive to
> me ... If I had my way I'd have the
> front wheel do the aperture and the
> rear wheel do the shutter.)

My sentiments exactly! Just WHY did suddenly all D-SLR manufacturers agree to set up these vital control elements the wrong way? I don't get it ...

Thankfully, my camera (Konica-Minolta Dynax 7D) allows to swap the two controls in the set-up menu ... which was the first thing I did when the camera was new.

-- Olaf

9:35 AM  
Blogger Peter said...

my camera (Konica-Minolta Dynax 7D) allows to swap the two controls in the set-up menu

If the Pentax can't do this I'll be sorely disappointed, my A1 did this 2.5 years ago.

That being said, I'm not quite understanding what it is about this green button. Are you saying it basically functions like an AE lock?

9:54 AM  
Blogger Al Benas said...

Maybe I'm missing something, and I really don't mean to start a "my daddy can beat your daddy" war, but on my Nikon D70, D70s & D200, in M mode, the rear wheel is shutter speed and the front wheel is aperture. That's not to say I won't enjoy a shutter wheel and a lens aperture ring. Maybe they should make a special order "old guy's model";)

10:02 AM  
Blogger Carl Weese said...


Unless I'm missing something, neither the E1 nor the K10D allows you to switch the wheel functions, but if it turns out it *can* be done I'll switch immediately.

10:43 AM  
Anonymous Anonymous said...

I'm pretty sure this started with Canon, which was the first to introduce front and rear control dials for their SLRs. With most Canon EOS SLRs the front dial controls the aperture when you're in AV mode but the shutter when you're in TV or M mode. The EOS 1n and 1v allowed you to set up either dial to exclusively control either the aperture or shutter. This common sense convenience is absent on Canon's prosumer DSLRs.

FWIW, Nikon DSLRs that have two control dials use the front for aperture and the rear for the shutter, regardless of whether you're in AV, TV, or M mode.

10:58 AM  
Blogger promenadeur said...


I hope, I understood your explanations correctly.
However I consider it more logical, after a view on the histogram, to change from the automatic mode in the manual mode. One can take f-stop and shutter speed from the automatic mode, and then correct fast as desired. I often use this function. And constantly exposed pictures, provided with a constant white balance, are naturally easier to work on.

11:15 AM  
Blogger Tim Parkin said...

I'm glad one manufacturer is doing this.. I have a 5D and always use it in manual for landscapes but would love to be able to 'grab' some settings from Av mode as a starting point...

It's not hard to do this by hand, but a shortcut to set aperture appropriatly or set shutter appropriately would be cool...


11:17 AM  
Blogger ShadZee said...

In K10D individual Av and Tv modes you can change the e-dial (wheels) functions. For example in Av mode you could set the front wheel to change the Aperture, and in Tv mode you can set the back wheel to change the shutter speed.
You can also change the function of the Green button; you could set it to be in Program mode, or Av mode (fixing your Aperture) or in Tv mode.

But, my preferred mode is Av. I've set the back wheel to change the Aperture, and the front wheel to change exposure compensation.

Overall, the best mode in K10D IMO, is the Hyper Program. You can be in P mode, and still change the Aperture OR Shutter speed, and the camera will adjust the other ;-) It's like being in both Av and Tv modes at the same time.

12:02 PM  
Anonymous Anonymous said...

I agree with you Carl, a shutter dial and aperture ring are so simple to use, without conscious thought. Rolling the control three stops is one action, with the DSLR I often feel like I am winding a clock work toy to change three stops - or nine 1/3 stop steps...

It took auto makers years to realize that a common control layout leads to better driving. Digital camera makers have yet to learn less is more!


12:10 PM  
Blogger Carl Weese said...

"with the DSLR I often feel like I am winding a clock work toy to change three stops - or nine 1/3 stop steps..."

Eliminating this wheel-twirling is exactly what the green button is good for (in Hyper-Manual). When the light changes by a large increment, one push of the green button brings the exposure into line with no wheel-twirling. But you're back in manual as soon as you let go of the button, so if you tweak up or down the settings will stick.

2:48 PM  
Blogger nutty said...

"35mm cameras from the first Leica onwards have offered a shutter speed dial located near the shutter release, and an aperture ring on the lens."
Not my OM4! the shutter speed is another ring, this time on the lens mount. It's a piece of cake to move your left hand between aperture, focus and shuuter speed while your right hand works the spot meter and shutter release. It's probably the easiest camera to use I've ever tried, and easily the smallest SLR. The body fits in one pocket and the lens in another. The XA is another favourite from the past too.
Given the new Zuiko glass I half regret buying a D200 even though I love it. I'll always have a soft spot for Olympus.

3:33 PM  
Blogger RJ said...

Carl, you CAN do it with the K10D (check the manual).

You hav e4 different controls you can assign to any pf the twho wheels: Shutter, aperture, program shift and EV compensation and that in any xway you want !!

4:54 PM  
Blogger K said...


Have you taken a look at the Panasonic L1? It's got a shutter dial on top :)

6:44 PM  
Blogger Carl Weese said...


There are lots of options for what the wheels do in various auto functions, but none that let me switch the function of the front and back wheels in manual so that the shutter goes to the back wheel and the aperture to the front. If you've found that option, please tell me what page of the manual it's on.

nutty, I knew someone would point out the Olympus shutter ring on the lens mount. An early Contax had something remarkably like current dslr control wheels, too. But 99.999% of 35mm cameras used the standard layout initiated by Leica.

7:11 PM  
Blogger Joel said...

The K100d can do the same thing. You have to set it in the custom functions, I think, but then AE-L will do the same operation in manual mode.

It's the only way to get autoexposure with Pentax-M and screwmount lenses.


8:15 PM  
Blogger Just Plain Hugh said...

Like the Olympus, the Nikkormat had the shutter speed control concentric with the lens mount,

My favorite shutterspeed f/stop arrangement is on the older Hasselblad 500C/M where you first set the EV, then chose which shutterspeed f/stop combo you want. The EV value is conveniently what Gossen meters read directly without fiddling with the dial. It made mixed strobe and natural light super easy.
On the Canon 1DS you can do something like this. You put the camera in program mode, and set your choice of the front or back dial to control the exposure offset from what the lightmeter thinks is correct and the other dial to chose which shutterspeed f/stop combo you use. Unfortunately you can't use it that way manually, and changing the ISO involves pushing two buttons at once and looking at the top of the camera.
I'll stop before I get into my rant about 1DS so called ergonomics.

10:37 PM  
Blogger Peter said...

It's a bit of a tangent, but I find this whole discussion about control wheels facinating.

Let me start by saying first that I would like to have an aperture ring on my lenses. Switching from an RF to the dSLR is always a bit awkward because of this, and I would much prefer to have a real aperture ring on my lenses. This alone is a huge temptation of the new "Leicasonic" dSLR system, assuming all the new Leica lenses are going to have aperture rings.

(I'm working from memory here, so I might be lying, but...) on the Minolta A1 you had two control wheels, which was virtually unheard of in that class of camera at the time. I don't recall if any of it's direct competitors had dual control wheels when it came out.

Now the control wheels were completely configurable although various options may have been mutally exclusive. In manual exposure you could set front-SS and rear-FS (SS=shutter speed, FS=F-stop) and vice versa.
In the priority modes the default was to have both wheels control the parameter, depending on the mode, whether SS or FS, but you could also configure the camera to have one wheel be exposure compensation (EC). So you could set have front-FS (or SS) and rear-EC or front-EC and rear-FS (or SS). In manual, besides just configuring front/rear to your liking, you could also set one wheel to be EC and the other to be either SS (or FS), then to switch over to FS (or SS) with that wheel by pushing the EC button on the rear of the camera, under your thumb.

Basically you had complete control over the behavior of the two wheels (more or less), which makes sense because it's just software.
Also, after re-reading the bit about the green button, I get it now, it's like being able to configure the AF to trigger on a button press, but with the Program AE mode. That sounds like it could be pretty handy.

10:28 AM  
Blogger chrispycrunch said...

Is the 'AE-L' button on other dSLR the only thing that comes close to this green button option?

5:29 PM  
Blogger Nick Wright said...

Carl, it appears that the newest version of the firmware for your K10D allows you to choose which wheel controls which function. Just an fyi.

7:38 AM  

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