I’ve had my K-01 since March 2012. One of the reasons I bought it as soon as it was released was that I was having trouble manually focusing my legacy Pentax A and M and Takumar lenses with my K200D. I wear glasses, so even after installing an after-market focusing screen in the DSLR, I had too much trouble hitting focus, particularly with wider lenses. So the K-01, with its bright live view, focus zoom, and focus peaking, seemed like the ideal camera for that purpose.

And I can’t say I haven’t been pleased. As far as focusing goes, it can do just about everything I ask of it. But it has taken me a year to learn how to use the various types of manual-focus lenses with it. And at first it was something of a disappointment because the green button, which acted somewhat differently on my K200D (and, I understand, operates differently on most other Pentax DSLRs as well), didn’t play well with M42 lenses. With the earliest K-01 firmware, using the green button with a screw-mount lens, Pentax or otherwise, would freeze the exposure controls, requiring the camera to be turned off and back on again. An unannounced benefit of the firmware update 1.01 is that now, with M42 lenses, the green button works as it should.

So after over a year of occasional experimentation and reading about other users’ experiments—and with the firmware updates—here’s what I think I’ve learned about the use of manual-focus lenses with the K-01 and its green button. I originally wrote this article from my own perspective: I like to use manual-focus, manual-aperture lenses (mainly M42) manually—that is, set ISO, aperture, shutter speed (with or without the green button), focus, and shoot. And after a lifetime of shooting with film, I tend to think in terms of a fixed ASA (ISO) rating, so I’m still getting used to Auto ISO. But since posting the first version of this article I’ve found that many folks prefer to shoot in TAv mode: using Auto ISO to let the camera set the exposure. And I have to admit it does add another direction of flexibility. As a result, this edition of the article takes into account the Auto ISO option.

To get started, if your haven’t already, set your K-01 menu to
Custom 3 > 16. Using Aperture Ring > 2 Enable
Rec. Mode 3 > Button Customization > Green Button > Action in M/TAv Mode > Tv Shift

It's especially important that you upgrade your firmware to at least Firmware Release 1.01, which allows proper performance of the green button with screw-mount (M42) lenses (as well as other good things, such as faster action with auto-focus lenses).

Using Pentax-A Lenses with the Aperture Ring Set on “A”

Camera set on AV, TV, or P; manual ISO—
“AV,” “TV,” or “P” shows in the upper left corner of the LCD.

The camera will automatically select a proper aperture/shutter speed combination for the exposure value (EV) of the subject. Turn the thumbwheel to change the aperture (in AV mode), the shutter speed (in TV mode), or both (in P mode); the camera will maintain the proper EV by changing the corresponding aperture and/or shutter speed. The green button does nothing.

Press the +/- button to open an EV compensation scale that shows thumbwheel changes to shutter speed (in AV mode), aperture (in TV mode), or both (in P mode). Press the green button to recenter the EV compensation scale to ±0.0.

Press AF/AE-L to lock the selected EV or EV compensation (an asterisk appears in the bottom left corner of the LCD). Press again to unlock it.

Camera set on AV, TV, or P; Auto ISO—
“AV,” “TV,” or “P” shows on the LCD.

With Auto ISO set, the camera will automatically select a proper aperture, shutter speed, and ISO sensitivity. In AV mode, for any changes in aperture set with the wheel, ISO will remain at 200 (or 100 if the camera is set for low extended ISO range) until the shutter speed falls to 1/125, where it will hold while ISO begins to increase automatically. In TV mode, ISO will hold at 200 (or 100) and then begin to increase after the auto aperture setting reaches the lens’s widest aperture. In P mode the ISO will hold at 200 (or 100) and then begin to increase after the shutter speed reaches a minimum of 1/125 at the lens’s widest aperture.

Camera set on M; manual ISO set—
“M” shows on the LCD.

An EV compensation scale appears at the bottom of the screen. Select either aperture or shutter speed by pressing the +/- button. An arrow will appear next to the selection at the bottom of the LCD. Then use the wheel to set aperture or shutter speed for the desired EV compensation.

Press the green button to reset the shutter speed and return the EV compensation setting to ±0.0. Note that the green button does not reset the aperture, only the shutter speed, no matter which is selected by the +/- button.

If the AF/AE-L button is pressed (an asterisk appears in the bottom left corner of the LCD), the wheel changes aperture setting and shutter speed simultaneously to maintain the selected EV compensation.

Camera set on M; Auto ISO selected
“TAv” shows on the LCD.

Select either aperture or shutter speed by pressing the +/- button. A triangle will appear next to the selection at the bottom of the LCD. Then use the thumbwheel to select either aperture or shutter speed.

The camera automatically selects ISO for the shutter speed and aperture set with the wheel. The minimum ISO 200 (or 100 if the extended low ISO range is selected) will flash red when the low EV limit is reached.


Using Pentax-A, -M, and -K Lenses with the Aperture Set Manually on the Ring

When in AV mode or in M mode with Auto ISO, these lenses can't communicate aperture information to the camera. As a result, the camera holds the aperture wide open at all times. This may be what you want for closeups with shallow depth of field and bokeh, but if you want aperture control with these lenses, use M mode and set your ISO manually, or put tape over the lens mount contacts (see below).

Camera set on AV; manual ISO—
“Av” and “F--” show on the LCD.

The camera will hold the iris wide open no matter what aperture is set on the ring. The camera will automatically set the shutter speed for the proper EV at the widest aperture.

To control the exposure, press the +/- button, and an EV compensation scale will appear at the bottom of the LCD. Use the wheel and EV compensation scale to adjust shutter speed; press the green button to center the EV scale to ±0.0 and reset the shutter speed.

Camera set on AV; Auto ISO—
“Av” and “F--“ show on the LCD.

Again, the iris will be held wide open no matter what aperture is set on the ring. The camera will automatically set the ISO for the proper EV at the widest aperture. Shutter speed will hold at 1/125 until the ISO gets to 200 (or 100 if the low extended ISO range is selected), when with increasing brightness speed will begin to increase.

Press the +/- button, and an EV compensation scale will appear at the bottom of the LCD. Use the wheel and EV compensation scale to adjust ISO; press the green button to center the EV scale to ±0.0 and reset the ISO.

Camera set on M; manual ISO—
“M” and “F--” show on the LCD.

In this mode, with manual ISO, the camera allows the lens to stop down to the aperture set on the ring. Press the green button to set the shutter for a ±0.0 exposure. Or, using the “sunny 16” rule or a separate light meter, turn the thumbwheel to set the desired shutter speed appropriate for the aperture setting on the ring.

The +/- button does not bring up an EV compensation scale; instead, it stops down the aperture until released.

Camera set on M; Auto ISO—
“AV” and “F--” show on the LCD.

This setting is the same as selecting AV mode. The aperture will be wide open, and first shutter speed (down to 1/125) and then ISO will be adjusted automatically to compensate.

Tape over the camera lens mount contacts; camera set on AV—
“AV” and “F--” show on the LCD.

THoog and others have found that a piece of cellophane tape covering the electrical lens mount contacts allows their Pentax-A, -M, and -K lenses to stop down in AV mode.

The camera automatically sets the shutter speed (or shutter speed and then ISO if the camera is set for Auto ISO) for the aperture set on the ring.

Press the +/- button to show the EV compensation scale at the bottom of the LCD. Turn the thumbwheel to set the desired EV compensation. Press the green button to recenter the EV compensation scale to ±0.0.

Press AF/AE-L to lock the compensation setting. The wheel and the green button are then locked out.

Tape over the camera lens mount contacts; camera set on M—
“M” and “F--” show on the LCD.

Again, the tape allows the lens to stop down. In this case, though, with manually set ISO an EV scale appears automatically on the LCD. The green button sets the shutter speed, or the thumbwheel may be used to dial in compensation.

With Auto ISO set, “AV” appears on the LCD, and the camera operates just as above, when it is set on AV with tape.

Note: If you use tape, my advice is to clean the contact pins on the lens mount afterward. It’s been my experience that sticky tape residue can build up and interfere later with the operation of auto-aperture lenses.

Using Screw-mount M42 Lenses
(with the lens switch, if any, set on manual aperture)

M42 screw-mount lenses don’t have the lever that allows the camera body to control the aperture. And since most of them are painted or anodized on the mounting ring, or have a very narrow mounting ring (like the Helios 44-2) that doesn’t make contact with the lens mount pins, the camera doesn’t sense them, allowing them to be used stopped down in AV as well as M mode.

Camera set on AV, manual ISO—
“AV” and “F--“ show on the LCD.

The camera will automatically set the shutter speed. To control the shutter speed, press the +/- button, and an EV scale will appear at the bottom of the LCD. Use the wheel and EV scale to adjust shutter speed. Press the green button to center the EV scale to ±0.0 and reset the shutter speed. Press the +/- button again to lock the EV compensation selected.

Camera set on M, manual ISO—
“M” and “F--” show on the LCD.

An EV scale appears at the bottom of the LCD. Press the green button to set the correct shutter speed, or make manual adjustments to the shutter speed, as shown on the EV scale, with the wheel.

Camera set on M or AV, Auto ISO—
“AV” and “F--“ show on the LCD.

This combination works about the same as setting M mode with Auto ISO on an A, M, or K lens. For the set aperture, shutter speed changes automatically with decreasing brightness down to 1/125 second, where it holds and ISO begins to increase.

[nparsons13]

I should add that I don't own any K lenses, so I've assumed they act the same as M lenses. Someone who has K lenses: please test them out and post confirmation or correction.

[THoog]

K and M lenses are electrically/mechanically the same, so their behavior should be the same. I noticed you don't differentiate between autoISO and manually selected ISO in Manual mode. I think for green button metering to work as described, you have to have manually selected ISO.

[vonBaloney]

This is one of those topics that seems to mystify people for no apparent reason. Nothing here that can't be mastered in 15 minutes.

With 'A' lenses and newer, there is no reason to use the green button. With m42 lenses, there is also no reason to use the green button since Av mode is much easier. If you are partial to M mode, then ok, go ahead.

So the only time you *need* the green button is for M or K-series type lenses (K-mount, no contacts) where you really are forced to use M mode on the body and there is no other way to get it to take a reading at your selected aperture than to use the button. And yes, you do have to set your options correctly -- Aperture Enabled, Green Button set to Tv Shift for M/Tav. And on the K-01 you have to be sure to set the ISO to a fixed number. And although the menus are different for how you go about finding those options on the various models of bodies, once you have done so the actual metering procedure is the same with all models that I'm aware of. (Although I don't know anything about the 200D.) But the K10D, K-7, K-5, K-01, K-30, etc all act the same.

You put it M mode, set your aperture on the ring, and hit the green button to take a reading and set the shutter. Some models may allow you to dial in Ev comp into this equation, others you have to post-adjust. But pretty simple either way.

[nparsons13]

@THoog: Right, I usually select the ISO I want, so I should have made it clear at the beginning that these procedures are for manually set ISO. Including automatic ISO as an option would lengthen the list considerably. Maybe someone else would like to add that part?

@vonBaloney: Thanks for the nutshell summary. You're right, too. This should be quick and easy. But a lot of new K-01 users still seem to be confused by it. I wrote this after seeing another new thread on the subject a couple of days ago.

[vonBaloney]

@THoog: Right, I usually select the ISO I want, so I should have made it clear at the beginning that these procedures are for manually set ISO. Including automatic ISO as an option would lengthen the list considerably. Maybe someone else would like to add that part?

@vonBaloney: Thanks for the nutshell summary. You're right, too. This should be quick and easy. But a lot of new K-01 users still seem to be confused by it. I wrote this after seeing another new thread on the subject a couple of days ago.

On the K-01, if you put it on auto-ISO while you are in M mode, the green button will no longer function for metering/shutter speed because it treats that as Tav mode, which with a manual lens mounted is really Av mode and so only wide-open shooting is possible with non-'A' lenses bayonet lenses. On other models that have a Tav mode on the dial, it won't let you even select auto-ISO while in M.

[dgcom]

Interesting... I've seen this posted everywhere - for green button to work with M and K lens, you have to set its Action in M/TAv Mode to Tv Shift.
I just got K-01 and experimented a bit - both with 1.00 and 1.03 firmware and couple of manual lens.
I used Takumar 135/2.5 (but tried others too) and green button works properly - temporarily stopping down lens and metering - regardless of Action set, unless it is disabled by setting to off.
And I compared shutter speed set - it is the same (and correct) regardless to the setting.
I did this because for me, P LINE setting is more useful than Tv Shift...

I also tested M42 lens - Jupiter-9 and I think it is shorting contacts on the body... So in M, it operated exactly the same as K/M lens above - requiring green button press to set shutter speed.
However, there is no real reason (at least for me, unless M is really called for, but then I'll care less about what internal exposure meter have to say) to use it this way - screw mount lens automation is much better in Av mode, with exposure meter active and metering correctly automatically.
I have some other M42 lens I can try and see if behavior will change...

[kevinschoenmakers]

A question - the K-01 does not seem to open the lens aperture fully on an A-class lens when focussing (rather it seems to be at f5.6 or thereabouts). This is with the camera set to Av and the aperture ring set to 'A'. Doesn't this mean focussing for apertures wider than f5.6 is very difficult?

[vonBaloney]

A question - the K-01 does not seem to open the lens aperture fully on an A-class lens when focussing (rather it seems to be at f5.6 or thereabouts). This is with the camera set to Av and the aperture ring set to 'A'. Doesn't this mean focussing for apertures wider than f5.6 is very difficult?

It does that in bright light, although sometimes it seems to get stuck in that mode even in lower light. However, when using "manual assist" or whatever it is called (where you digitally zoom it in for focusing), it should open up all the way while that is engaged.

[PBandJ]

Even with DA lens, I think I've got it set right using focus peaking, but when I look at them on the laptop, they are blurry. I don't know what i'm doing wrong. I have a fast shutter speed and SR on..

[nparsons13]

Even with DA lens, I think I've got it set right using focus peaking, but when I look at them on the laptop, they are blurry. I don't know what i'm doing wrong. I have a fast shutter speed and SR on..

This problem is discussed in a couple of earlier threads in the K-01 section. There, it seems the user was setting a combination of low-medium ISO and fast shutter speed that was causing the camera to hold the aperture open wide--and most lenses aren't their sharpest wide open.

Take some shots in Av with the aperture stopped down to f/8 or smaller and see if you have the blur problem.

[PBandJ]

This problem is discussed in a couple of earlier threads in the K-01 section. There, it seems the user was setting a combination of low-medium ISO and fast shutter speed that was causing the camera to hold the aperture open wide--and most lenses aren't their sharpest wide open.

Take some shots in Av with the aperture stopped down to f/8 or smaller and see if you have the blur problem.

Thanks. I have forced it to stay on Iso 100. SR might very very well be part of it. I will also force f8--I was trying to get shallower DOF though

[dosdan]

Thanks. I have forced it to stay on Iso 100. SR might very very well be part of it. I will also force f8--I was trying to get shallower DOF though

No sure how low a f-stop you want to use to get a shallow DOF. With the K-01's max. shutter speed of 1/4000s and ISO100, you can cover 15 LV (bright daylight scene) at f/2.8. If you want to use a lower f-stop with this light level, e.g. f/1.4, you'd need to use an ND4 filter. (Or 1/2000s, f/1.4, ISO100 with ND8.)

However, the quality of light is better late/early in the day when the LV will be lower, and you then would not need a ND4/ND8 filter to use f/1.4 & ISO100.

Dan.

[oncount]

Thanks to those who mentioned manually selecting the ISO, the Green Button was driving me to abstraction. Simple step that I couldn't intuitively make.

[nparsons13]

I finally got around to revising and correcting the information in the article, including coverage of options for Auto ISO settings.

Thanks to everyone who provided feedback on errors and gaps. And again, let me have your feedback if you find problems with this version.

Noel