[Smolk]

There is no extra step:

1. Set f-stop on aperture ring.
2. Set f-stop value on eDial (optional, if you want the actual aperture recorded among EXIF data).
3. Frame.
4. Press shutter.

instead of:

1. Set f-stop on aperture ring.
2. Frame.
3. Press green button.
4. Press shutter.

In other words, if you don't need the f-stop recorded, or want to save time, you just have three steps which are essentially the same as with any other lens.
Assuming you know approximately what f-stop is needed or desirable, which is normal.

[torge]

anyone noticed that they use a M42 lens in the article?
where K-mount cameras ever able to stop those down?

[Smolk]

anyone noticed that they use a M42 lens in the article?
where K-mount cameras ever able to stop those down?

Green button metering, but in addition, these lenses can be set to manual aperture opening, hence meter with Av priority (unlike K and M lenses)

[Not a Number]

I think you are misreading the article. No need for green button in Av or TAv modes.

"When using some older lenses, such as M-series lenses or A-series lenses with a lens aperture ring, previous models provided automatic exposure setting with closed-down metering, made possible by pressing the Green button in the manual-exposure mode. Designed to automatically perform closed-down metering at the moment of shutter release, the PENTAX K-3 Mark III also provides automatic exposure setting in the Av and TAv modes while the photographer sets the desired aperture using the lens aperture ring. During Live View photography, it also makes real-aperture metering for the aperture set on the lens aperture ring."

How is that going to work? The camera has no way of reading what the aperture is actually set to thus cannot show what shutter speed or ISO is selected for the exposure if the aperture is not stopped down to measure the amount of light coming through the lens. Minolta had a "final check" system that would take one last meter reading just before the shutter was released but again this wouldn't show you what the exposure settings were so you could decide to change them.

If the aperture linkage has been added (un-crippled mount) then there would be no need use the eDial.

If the eDial f-stop setting influences the shutter speed or ISO as it does with "A" lenses and you set the actual f-stop with the ring then there is the potential for exposure mis-match. Example: AV mode, IS0 100, sunny day. eDial set to show f16, lens set to f2.8. Meter selects ~1/100th sec shutter speed (sunny 16 rule to simplify things). Take the exposure. One of two things happen:
a) the exposure is taken at ~1/100th and the aperture closes down to f2.8. (5 stop overexposure) - f16 recorded
b) aperture closes to f2.8, meter reading taken and the shutter is set to 1/3200th - proper exposure.- f16 recorded

If it is a matter of making a M or K series lens behave like an "A" lens then you would have to enter into the camera the min and max f-stop settings for the lens and set the aperture to the highest setting (e.g. f16,22, or 32). After that just treat it like an "A" series lens. But again it's not that simple as the M and K lenses were not designed to accurately set the f-stop from the stop down lever. That's why people haven't been adding insulators to the mount base to encode the f-stop range and shorting out the "A" pin.

[Not a Number]

My understanding is that prior to the A series the normal action for the aperture lever on M and K lenses is that the linear movement that would create a change in aperture causes the diameter to change such that moving x distance and 2x distance gives a diameter of y and 1/2 y. The A series is supposed to be based on area rather than diameter which is more easily tied to f stops.

I am too sleepy to look for the source and I might be explaining it badly.

I've read that too. I'd be interested in seeing the source for that information as well.

Basing the f-stop position on area would make sense as the area changes in proportion to the square root of 2 (1.41) - the same as f-stops.

[reh321]

anyone noticed that they use a M42 lens in the article?
where K-mount cameras ever able to stop those down?

The Takumar M42-mount lenses had a pin used to stop down the lens, which was not compatible with the levers used by K-mount lenses,
so M42-mount lenses have always been used fully stopped down to the shooting f-stop for both composing/metering and shooting.

[TwoUptons]

In other words, if you don't need the f-stop recorded, or want to save time, you just have three steps which are essentially the same as with any other lens.
Assuming you know approximately what f-stop is needed or desirable, which is normal.

Yes, if you don't care about having the aperture data in the Exif, you can just shoot:
1) Set f-stop on aperture ring
2) Frame
3) Press shutter

The difference is that currently, none of the cameras know what you are doing when you are in Av mode or TAv mode.
Current cameras cannot properly calculate exposure without the separate step of using "green button" metering.
And for those of us who extensively use old or adapted lenses and want to use Av or TAv, this is annoying

The new camera is supposed to be able to stop the lens down and take a meter reading fast enough to set the shutter speed (in Av mode) as well as (in Tav mode) the sensor ISO to properly expose the photo with the aperture you just set.
Most of us will try and set the lens aperture in the Exif if we care to remember how we did things, but that part seems to be separate from the mechanics of metering (which I consider a good thing).

-Eric

[Not a Number]

Other things to consider:

Since there is no peephole periscope to show the aperture ring setting in the viewfinder as there was on some MF SLRs you have to either look at the ring or count clicks to know what the ring is set at to transfer that to the eDial setting.

And is the eDial always set to 1/2 stop intervals or depending on the stop interval settings in the menus. The camera can be set to 1/2 or 1/3 intervals. MF lenses are in 1/2 stop intervals except that the high end where it is one stop. The lower-end depends on what the widest aperture.

[stevebrot]

However, in Av mode, the shutter speed would be determined only at the time of exposure, and would not be apparent to the photographer until after the shot has been taken. Not knowing one of the primary exposure elements prior to pressing the shutter button would seem to be inelegant in cases when the photographer's choice of aperture leads to an inappropriate shutter speed. Am I missing a key point here?

No, you are getting it and that is why I think that approach is brain dead when the camera already has the information to set the appropriate shutter speed in Av mode.

Several years ago, a hack was published on this site that was impractical, but worked. It went like this:

1. Using foil, short the mount contacts to code for an A-contact lens with maximum f1.4 and minimum f/22.
2. With lens mounted the camera in Av mode, the camera will allow setting from f/1.4 to f/22.
3. Set the lens aperture ring to f/5.6 and dial f/5.6 into the camera using the e-dial. The camera will respond with an appropriate shutter speed.
4. Make an exposure

This only works with lenses that do a full stop-down with minimum actuator travel, but does work. In addition, so does exposure compensation and bracketing. The takeaway is that the body only needs to know the setting in order to properly assign a shutter speed.

Assuming that the user did dial an aperture value in, the camera my still support a stop-down measurement in real time with set aperture and metered shutter speed unknown at the time of exposure.


Steve

[pschlute]

How is that going to work? The camera has no way of reading what the aperture is actually set to thus cannot show what shutter speed or ISO is selected for the exposure if the aperture is not stopped down to measure the amount of light coming through the lens

It will work as the article says. The meter reading is taken after the lens is stopped down, just before the shutter is tripped. You won't know the shutter/ISO value until after the capture. If that is a problem you can either take a picture and review the result, or use M mode instead with the green button as it works with current models.

This is added functionality with older lenses, not perfect, but still a welcome one in my view.

A thought has just occurred to me. I wonder if the DOF preview will play any role with the new functionality. With current models in M mode, one can use the DOF preview to turn on the meter with K and M lenses and make adjustments to centre the meter. If the new implementation allows the DOF preview to turn on the meter, you may be able to see the shutter speed/ISO before you capture the shot ? Or maybe the green button does have a role in the new camera in TAv/Av mode with old lenses, allowing you to see the parameters chosen by the camera before you take the shot.

Either way, unless you are shooting in drastically changing light, your first shot will tell you if you all you need to know.

---------- Post added 12-27-20 at 07:57 AM ----------

Since there is no peephole periscope to show the aperture ring setting in the viewfinder as there was on some MF SLRs you have to either look at the ring or count clicks to know what the ring is set at to transfer that to the eDial setting.

My old Z-1 had the KAF2 mount, so I was able to use Av mode with open aperture metering with K/M lenses. The shutter speed was indicated in the viewfinder, but not the aperture, and without a Judas window I had to count click stops or look at the lens to determine it.

[Smolk]

But half-way pressing the release button, why would the shutter speed not show up? It is lens-independent. That the aperture is unknown, fair enough.

My old Z-1 has the KAF2 mount.

[pschlute]

But half-way pressing the release button, why would the shutter speed not show up? It is lens-independent. That the aperture is unknown, fair enough.

On the new K3III the shutter speed will show in TAv mode. In Av mode I am not sure. On current camera models it does but that is because the camera only shoots wide open in Av mode.

[Breakfastographer]

Seems like there's still no word on whether focal lengths shorter than 10mm are now fully compatible.

[Ishpuini]

My current favourite lens is the K50/1.2. Easy to see why I would love this feature. Curious to see what other new undetected features the K-3III holds... It is getting easier and easier to get over losing GPS...

Wim

[repaap]

My current favourite lens is the K50/1.2. Easy to see why I would love this feature. Curious to see what other new undetected features the K-3III holds... It is getting easier and easier to get over losing GPS...

Wim

What GPS?