[mjp29]

k-R user

When shooting with a manual lens, is there a way to have the camera automatically select the ISO?
In manual mode, it doesn't seem so
?

[pschlute]

k-R user

When shooting with a manual lens, is there a way to have the camera automatically select the ISO?
In manual mode, it doesn't seem so
?

The answer is a qualified....NO

Pentax DSLR cameras do not have auto-ISO in Manual mode even with a modern lens. Pentax created a specific mode for that called TAv.

When you use a manual lens the camera does not know the aperture you have set on the lens. So you need to use Manual mode if you want to use stop down metering, and even if you dont you need to use manual mode to get the lens to stop down during capture. ISO will be fixed.

If you do try to put the camra into any other auto mode (Tv/TAv/P/Av), it will default to Av. In this mode I believe the camera will use auto-ISO if selected (not 100% sure), but the problem is that all your pictures will be at max aperture.

[Benedict Michael]

Manual mode is manual mode. You control aperture, shutter and ISO!


Drives me crazy teaching basic photography classes when I have to show students with Nikon & Canon how to set ISO to manual instead of the default, Auto ISO.


Manual exposure is, well manual exposure. It wasn't an issue with film!

[UncleVanya]

The answer is a qualified....NO

Pentax DSLR cameras do not have auto-ISO in Manual mode even with a modern lens. Pentax created a specific mode for that called TAv.

Right, and some consumer models like the k-50 offer auto iso in m mode as a way to enable TAv mode. It looks like you’re setting m mode with auto iso, but is subtly different.

[K(s)evin]

Right, and some consumer models like the k-50 offer auto iso in m mode as a way to enable TAv mode. It looks like you’re setting m mode with auto iso, but is subtly different.

I know that the K-01 offers autoISO in manual mode to access TAv, as there is no option for it on the mode dial.

[Not a Number]

Your manual focus lens needs to have electrical contacts (KA mount) and be set to "A" in order to use TAv.

[aslyfox]

in case the OP needs a copy

http://www.ricoh-imaging.co.jp/english/support/man-pdf/k-r.pdf

the owners reviews and an in depth review can be found here

Pentax K-r - Pentax K-mount DSLRs - Pentax Camera Reviews and Specifications

[mjp29]

The answer is a qualified....NO

Pentax DSLR cameras do not have auto-ISO in Manual mode even with a modern lens. Pentax created a specific mode for that called TAv.

When you use a manual lens the camera does not know the aperture you have set on the lens. So you need to use Manual mode if you want to use stop down metering, and even if you dont you need to use manual mode to get the lens to stop down during capture. ISO will be fixed.

If you do try to put the camra into any other auto mode (Tv/TAv/P/Av), it will default to Av. In this mode I believe the camera will use auto-ISO if selected (not 100% sure), but the problem is that all your pictures will be at max aperture.

ok, so one simply can't do it with the k-r.

Some of what you typed confuses me, as I don't see how the camera can "stop down" or force a picture to be taken at max aperture, with a manual lens, where I control the aperture with the aperture ring.

[aslyfox]

I have found these charts to be very helpful:


Pentax K-Mount Lenses Explained: The differences between various Pentax lens series

The Pentax K-mount Camera Lens Compatibility Chart

[Just1MoreDave]

ok, so one simply can't do it with the k-r.

Some of what you typed confuses me, as I don't see how the camera can "stop down" or force a picture to be taken at max aperture, with a manual lens, where I control the aperture with the aperture ring.

The aperture is overly complicated because it evolved and each advance retained some backward compatibility.

I want to start with the K-mount to save typing. (Before that is a whole different story.) The original K-mount cameras had a simple arm to push the aperture lever on the lens. The arm only has two positions. The first position opens the lens aperture fully. That makes it easier to frame and focus. The second position releases the spring-loaded lever to allow the aperture to close. The aperture ring on the lens controls how much the lens stops down. The camera arm stays in the first position normally. When you press the shutter button, the arm goes to the second position. The second position is also used if your camera had a depth of field preview switch.

Mechanically the K and M lenses are the same. The original cameras also had another arm that fit into a groove on the lens mount. A tab on the lens moves with the aperture ring, so the camera's meter can tell where the aperture ring is.

Everything is awesome new technology for a few years but then the world decides it would be cool for various reasons if the camera body could have full control over the lens aperture. The K-mount is only a few years old so users would be annoyed if Pentax orphaned those new lenses, so the system has to be compatible. The solution was to redesign the camera arm to be way more complicated. Now it can move in many small precise increments between the previous two positions. Those precise movements can move the blades precisely. The A-series lenses had to be designed to translate that movement accurately into stops, which was not important earlier. The camera needed more information about each lens so the lenses had a set of electrical contacts to tell the camera what their aperture range was.

At this point (early 80s), the camera's arm that followed the aperture ring position was only necessary for backward compatibility with K or M lenses. When those lenses were used, the new camera body worked exactly like an original K-mount body. When new A-series lenses were used, the new cameras could control the aperture with the precise arm. That allows more program automation and better metering. Program modes didn't work with the K or M lenses.

When autofocus became a thing, Pentax changed the way the electrical contacts were used (F-series). All the lens information was now sent to the body through a data pin. More lens information can be sent to the camera. The A-series system had no way to handle variable aperture zooms or lenses whose wide open aperture was on the third-stop scale. The Pentax-A* 135mm f1.8 can only tell the camera that its maximum aperture is f1.7.

Pentax started leaving the aperture ring detection arm off some cheaper cameras, nicknamed the crippled mount. That's when K or M lenses became harder to use.

That was the state of things when Pentax started designing DSLRs. They released the first model, the *ist D, with the crippled mount and no K/M lens compatibility. A firmware upgrade allowed the green button to tell the arm to turn back into an on-off switch, which is enough to use those lenses. This is a compromise and only works in M mode. The other modes don't work because they need more information about the lens, and the camera doesn't want to guess.

So if you use a K or M lens on a Pentax DSLR, the camera's arm only works in two positions, like the original K-mount. The camera doesn't know any lens information so metering is not "live". There's a compromise to meter with the green button, which moves the arm and measures the light. The camera also moves the arm in that on-off way when you shoot. The metering switches out of matrix metering to center weighted. The flash switches to fire at full power. The central AF point is active to indicate sharp focus.

A few new lenses have a fully electronic aperture, so no more levers. But they won't work on the K-r.

There's some indication that the K-3 iii will improve on this system. It'll be interesting to see how.

[pschlute]

Some of what you typed confuses me, as I don't see how the camera can "stop down" or force a picture to be taken at max aperture, with a manual lens, where I control the aperture with the aperture ring.

When your manual K-mount lens is on the camera, the aperture will be wide open. In Manual mode the camera will stop the lens down on capture to what you have selected on the lens aperture ring. If you try and use Av mode it will remain wide open irrespective of where the aperture ring is set.

M42 lenses are different. What lens are you actually using.

[AgentL]

I know that the K-01 offers autoISO in manual mode to access TAv, as there is no option for it on the mode dial.

Same with the GR III. It's fine with me.

---------- Post added 01-28-21 at 01:16 PM ----------

When your manual K-mount lens is on the camera, the aperture will be wide open. In Manual mode the camera will stop the lens down on capture to what you have selected on the lens aperture ring. If you try and use Av mode it will remain wide open irrespective of where the aperture ring is set.

M42 lenses are different. What lens are you actually using.

So M mode with a manual lens is more like A mode without automatic metering (except for the green button)? i.e. I'll be setting aperture on the lens to whatever I wish, but then green button will pick a shutter speed, and I can then deviate from that shutter speed as I want? Does the camera body remember to consider EV comp when the green button is pressed?

[aslyfox]

. . . So M mode with a manual lens is more like A mode without automatic metering (except for the green button)? i.e. I'll be setting aperture on the lens to whatever I wish, but then green button will pick a shutter speed, and I can then deviate from that shutter speed as I want? Does the camera body remember to consider EV comp when the green button is pressed?

perhaps these articles might be of interest:

Pentax Green Button Guide
A look at one of Pentax's secrets
By johnhilvert in Articles and Tips on Aug 15, 2016

. . . 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.. . .

Read more at: Pentax Green Button Guide - Articles and Tips | PentaxForums.com

________________________________

How to Use Manual Lenses on Pentax DSLRs
Virtually all K-mount and M42 lenses are compatible!
By PF Staff in Tutorial Videos on Apr 29, 2013

Read more at: https://www.pentaxforums.com/articles/tutorial-videos/how-to-use-manual-lene...#ixzz6ksgP8mBs

[Wasp]

I have a different use case for auto ISO. It is very handy when I mount a K mount lens via an adapter on my mirrorless Samsung NX1 bodies. Aperture is fully manual of course. To prevent camera shake I set the mode to shutter priority and dial in a speed speed suited to the focal length.The camera cannot change the aperture so it changes the ISO to get the exposure right. Works like a charm in low light, although you have to keep an eye out for excessively high ISO. In bright light you have to stop down or set the speed high enough, so I don't use it much in such situations. Aperture priority mode works better for that.

[pschlute]

So M mode with a manual lens is more like A mode without automatic metering (except for the green button)? i.e. I'll be setting aperture on the lens to whatever I wish, but then green button will pick a shutter speed, and I can then deviate from that shutter speed as I want?

Yes, when you press the green button in M mode , the camera stops the lens down, takes a meter reading and sets a shutter speed (which you are liberty to change). You can also meter by moving the DOF preview lever, then you will see the light meter on the lcd screen and in the viewfinder....move the shutter speed yourself to get a centred reading.

This applies to K-mount manual lenses, "K" and M series, and any later lens (A/F/FA) when the aperture ring is off the "A" setting.

Does the camera body remember to consider EV comp when the green button is pressed?

Earlier Pentax DSLRs did not allow exposure compensation in M mode. Later models do. When you dial in EC the metered centre position is shifted accordingly. You will need to check your camera model. But if you are working with a manual lens in M mode, the quickest EC is your right forefinger or left hand