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12-27-2020, 06:07 PM   #106
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QuoteOriginally posted by Breakfastographer Quote
Thanks.
I updated my response.

The K10D (first model with SR) also supported 8mm. At least I was able to set such with my Rokinon 8mm fisheye.


Steve

12-27-2020, 06:12 PM   #107
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QuoteOriginally posted by stevebrot Quote
I think you are probably right and I have probably been not thinking clearly due to wishful thinking. Yes, the system needs to know the offset from maximum aperture to calculate the shutter speed unless the lens is at maximum aperture.


Steve
I don't think it needs to know anything about the absolute or relative value of the lens aperture to set the shutter speed.

If the system can stop down, then measure the amount of light, it's basically trivial. This is how the camera does it for M42 lenses now, just with human intervention to do the stopping down...

As I understand the system, the camera stops down the lens to whatever it has been set to, then takes a meter reading, which informs the shutter speed and ISO settings according to whatever program line is in place.

The only part I don't get is where the meter reading is coming from at that point.

Is the camera stopping down, metering, then flipping the mirror up? That sounds time-consuming...

Or is it metering off the main sensor, as it would do in live view?
So stop down, mirror up, shutter opens, meter reading, camera picks shutter and ISO as appropriate, then shutter closes?

That gets complicated... and would require the electronic shutter, not just the mechanical one...

-Eric
12-27-2020, 06:30 PM   #108
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QuoteOriginally posted by TwoUptons Quote
I don't think it needs to know anything about the absolute or relative value of the lens aperture to set the shutter speed.

If the system can stop down, then measure the amount of light, it's basically trivial. This is how the camera does it for M42 lenses now, just with human intervention to do the stopping down...
My understanding is that the magic of aperture coupling, in those cameras were it was fully working, was that the camera could meter correctly without needing to stop down based on knowing what aperture it was at and what it would be stopped down to. This magical way of working is why people want it back.

Compared to your m42 example, the advantage is that you wouldn't have to look through a stopped down lens in the VF - or to focus first with aperture open, then stop down to meter, which, yes, you can do manually on m42, but it's still an extra step and violates the "don't make me think" principle.

---------- Post added 12-27-20 at 06:43 PM ----------

QuoteOriginally posted by stevebrot Quote
K-3 and newer for sure.

Addendum: For me, K10D used with the Rokinon 8/3.5 Fisheye (Rokinon (Samyang) 8mm Fisheye | Flickr no scripts run or edits to the EXIF except for final image.)


Steve

QuoteOriginally posted by stevebrot Quote
I updated my response.

The K10D (first model with SR) also supported 8mm. At least I was able to set such with my Rokinon 8mm fisheye.


Steve
Hmm... I'm not sure exactly what to think. One of the reports for the 8-16mm Sigma complains of the problem, states using the K-3 but does not state that the problem is absent on the K-3:
Sigma 8-16mm F4.5-5.6 DC HSM Lens Reviews - Sigma Lenses - Pentax Lens Review Database

He does say he also uses the K-5, but if you're listing it as not working, it would seem to make sense to also state if one of your cameras is an exception.

The other four reviews that complain of the problem do not list the camera used.
12-27-2020, 07:06 PM   #109
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QuoteOriginally posted by TwoUptons Quote
I don't think it needs to know anything about the absolute or relative value of the lens aperture to set the shutter speed.
I think you missed some of the context. Steve was wondering why if you set the aperture it wouldn’t be able to calculate exposure without stopping down. But as I pointed out the camera needs some idea what the wide open aperture is (which modern and A series lenses provide in one way or another without the coupler) to understand exposure.

QuoteOriginally posted by TwoUptons Quote
If the system can stop down, then measure the amount of light, it's basically trivial. This is how the camera does it for M42 lenses now, just with human intervention to do the stopping down...

As I understand the system, the camera stops down the lens to whatever it has been set to, then takes a meter reading, which informs the shutter speed and ISO settings according to whatever program line is in place.

The only part I don't get is where the meter reading is coming from at that point.
These aren’t mirrorless cameras, I suspect meetering is done with the mirror down even when stopping down. Think of it as a version of optical preview just for the meter.

QuoteOriginally posted by TwoUptons Quote
Is the camera stopping down, metering, then flipping the mirror up? That sounds time-consuming...

Or is it metering off the main sensor, as it would do in live view?
So stop down, mirror up, shutter opens, meter reading, camera picks shutter and ISO as appropriate, then shutter closes?

That gets complicated... and would require the electronic shutter, not just the mechanical one...

-Eric
I think it is the former. But recall this version of the camera can fire 12 frames a second without missing a beat. This is a fast mirror and shutter.

12-27-2020, 07:16 PM   #110
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QuoteOriginally posted by Breakfastographer Quote
My understanding is that the magic of aperture coupling, in those cameras were it was fully working, was that the camera could meter correctly without needing to stop down based on knowing what aperture it was at and what it would be stopped down to. This magical way of working is why people want it back.
Sort of...

The coupling camera-side drives a linear-form variable resistor mounted on a curved carriage that resides just under the upper part of the mount just above the top edge of the mirror box. There is a set of feeler contacts that ride on the surface of the resistor to bias the meter voltage based on position of the carriage under the feelers. At no point is the actual aperture (relative or absolute) setting known to the exposure system nor is the maximum aperture known. The electronics are exceedingly simple and essentially analog.

Note: An M42 adapter engages the coupler to allow emulation of a lens set wide-open.


Steve

Last edited by stevebrot; 12-27-2020 at 08:02 PM. Reason: Late additions...sorry :(
12-27-2020, 07:22 PM   #111
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QuoteOriginally posted by Breakfastographer Quote
Hmm... I'm not sure exactly what to think. One of the reports for the 8-16mm Sigma complains of the problem, states using the K-3 but does not state that the problem is absent on the K-3:
Zooms AF and KA2 lenses report their current focal length to the camera via the data contact on the mount. Perhaps Sigma was not reporting below 10mm?

As I mentioned on my second comment, SR setting support for 8mm goes back to 2006 on the K10D and you can't go any further back than that for SR support.


Steve

Last edited by stevebrot; 12-27-2020 at 07:50 PM.
12-27-2020, 10:11 PM   #112
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Just letting you guys know that an interesting discussion has developed on the other forum about how the features discussed in this product story might be further enhanced.

12-28-2020, 12:29 AM   #113
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Wish Ricoh would firmware update their previous cameras for some of these features. Being able to more easily use my non A k mount lenses more easily would be great with my KP.

But it's nice to see that Pentax finally has a camera usable for video. Mechanical stabilization should have never gone away in video.
12-28-2020, 04:01 AM   #114
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QuoteOriginally posted by ZombieArmy Quote
Wish Ricoh would firmware update their previous cameras for some of these features. Being able to more easily use my non A k mount lenses more easily would be great with my KP.

But it's nice to see that Pentax finally has a camera usable for video. Mechanical stabilization should have never gone away in video.
I know. I think it is probable that older cameras don't have the processing power to do this sort of thing though. We may see some of these features creep into the models that follow the K-70/KP/K-1 II, but I doubt they will backward port them to older models.

(It would take away work being done on new stuff and I don't know that the functionality would really be there).
12-28-2020, 04:08 AM - 1 Like   #115
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QuoteOriginally posted by ZombieArmy Quote
Wish Ricoh would firmware update their previous cameras for some of these features. Being able to more easily use my non A k mount lenses more easily would be great with my KP.

But it's nice to see that Pentax finally has a camera usable for video. Mechanical stabilization should have never gone away in video.
They want to sell new camera ........
12-28-2020, 04:37 AM   #116
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QuoteOriginally posted by Breakfastographer Quote
My understanding is that the magic of aperture coupling, in those cameras were it was fully working, was that the camera could meter correctly without needing to stop down based on knowing what aperture it was at and what it would be stopped down to. This magical way of working is why people want it back.
That is how it worked on my Z1 with a manual lens. Open aperture metering in Av mode with the shutter speed visible in the viewfinder.

---------- Post added 12-28-20 at 11:50 AM ----------

QuoteOriginally posted by TwoUptons Quote
The only part I don't get is where the meter reading is coming from at that point.

Is the camera stopping down, metering, then flipping the mirror up? That sounds time-consuming.
From the linked article, it suggests this is exactly how it works. Although it sounds time consuming I don't think it will be. I mentioned before to compare how the current cameras works in P-TTL mode.... Press shutter...flash emits pre-flash...meter reads pre-flash and calculates some combination of shutter speed/aperture/ISO/flash power (depending on mode and ambient light)....flips mirror....stops down lens...triggers shutter. Yet this all happens in an instant.
12-28-2020, 06:14 AM   #117
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QuoteOriginally posted by Larrymc Quote
or maybe no GPS!!
If there is an Astrotracer Menu, then there is (perhaps) GPS...

Last edited by fs999; 12-28-2020 at 06:20 AM. Reason: Perhaps
12-28-2020, 06:15 AM   #118
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QuoteOriginally posted by bobmaxja Quote
They want to sell new camera ........
I don't think people who bought a camera a few years ago are really the target demographic of this camera to begin with. It's trying to catch people from other mounts and people upgrading from the now pretty dated K3 SKUs. It's pretty much expected in any tech industry to to support your product at least for a few years with updates...

Plus if they really wanted to sell this as a feature maybe they should bring back the aperture coupling eh?

---------- Post added 12-28-20 at 08:16 AM ----------

QuoteOriginally posted by fs999 Quote
If there is an Astrotracer Menu, then there is GPS...
My KP has an astrotracer menu and no built in GPS.
12-28-2020, 06:19 AM   #119
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QuoteOriginally posted by ZombieArmy Quote
My KP has an astrotracer menu and no built in GPS.
That's sad news... At least the O-GPS1 module can be used...

Edit : But if the menu is not greyed then a GPS module is present...
12-28-2020, 07:03 AM   #120
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QuoteOriginally posted by fs999 Quote
Edit : But if the menu is not greyed then a GPS module is present...
Or, as already suggested, present but in a connected phone.
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