Green Button Metering Wish

troika · 04-01-2015, 09:32 AM

Just a thought I had, don't know if this is the right place to post and hopefully this hasn't already been discussed ad nauseam.

I use the green button frequently to meter K and M lenses. It's a good feature. What would make it better for me is if it changed ISO to get me to my desired exposure rather than shutter speed. Normally, I've chosen aperture for the photo I want, sometimes I may be willing to move it a stop or so after I meter to get to where I want to be. I usually either set the shutter speed to the slowest position that I think I can get away with for that lens (if handheld) or based on what's appropriate for what I'm shooting.

I want the ISO to be as low as possible, but for most exposures, it's the corner of the exposure triangle that I'm most flexible on, which is why I like Tav mode with A lenses. I suppose better still if I could choose which of those two things the green button changes (maybe I should check the menu to make sure I can't).

As it is, I chose an ISO that I think might be appropriate, then set aperture and shutter speed and then meter and adjust. It will change the shutter speed for me, but frequently, I change it back and then adjust ISO and maybe aperture by the corresponding number of stops and maybe or maybe don't remeter depending on what I'm shooting. If what I'm photographing is pretty consistent light-wise, it's really not a big deal once I'm dialed it.

Just ruminations. Wonder how others of you might have worked this feature.

**Lowell Goudge** · 04-01-2015, 09:34 AM

I don't know about all cameras, but in manual mode, there is no auto ISO. I understand the objective though. Many times you can have the shutter speed get set far too low, for the subject when aperture is fixed,

**jatrax** · 04-01-2015, 09:43 AM

I usually approach this by setting the ISO first, in the ball park, of where I know I'll need to be for conditions. Then set aperture for creative reasons and then meter for the shutter speed. But I can see the reasoning behind your idea. It would not be impossible to implement then have green button button metering configurable in the menu to which of the three you want to change.

But I suspect that would be low on the do to list for Ricoh. Not many new lenses made that require stop down metering

.

stevebrot · 04-01-2015, 09:49 AM

Originally posted by troika

I use the green button frequently to meter K and M lenses. It's a good feature. What would make it better for me is if it changed ISO to get me to my desired exposure rather than shutter speed.

Hmmmm...that would be an interesting twist, though I am not sure how it would be implemented, perhaps using the optical DOF preview and a special custom menu setting?

BTW...thanks to this question, I just discovered a previously unknown (at least to me) feature of the K-3 when using M-42 lenses. In Av mode you can switch to auto-ISO and the camera assumes a program mode with aperture floating freely and the shutter speed changing only as needed. Very cool.

Steve

**Lowell Goudge** · 04-01-2015, 09:54 AM

Originally posted by stevebrot

Hmmmm...that would be an interesting twist, though I am not sure how it would be implemented, perhaps using the optical DOF preview and a special custom menu setting?

BTW...thanks to this question, I just discovered a previously unknown (at least to me) feature of the K-3 when using M-42 lenses. In Av mode you can switch to auto-ISO and the camera assumes a program mode with aperture floating freely and the shutter speed changing only as needed. Very cool.

Steve

Implementation would be easy, today, when you stop down with green button, it measures the light through the lens, and using the ISO setting calculates shutter speed, no big deal to impose shutter speed and let it calculate the needed ISO within range of the auto ISO setting, and only if ISO would be outside the range, set the shutter speed as required, slower if ISO at maximum, faster if ISO is at minimum, to still make exposure.

As for the use of AV mode and auto ISO this is how I shoot most of the time with M42 lenses. It is a sort of TAV mode

Note that the Q allows auto ISO in manual

troika · 04-01-2015, 10:01 AM

Originally posted by jatrax

...

But I suspect that would be low on the do to list for Ricoh. Not many new lenses made that require stop down metering

.

I just scrolled through the menu function to make sure I wasn't missing a setting, but I don't see anything. Yes, I expect it is low on the feature list for the reasons you said, but one of the great things about Pentax is how far they've come to enable backward compatibility to old lenses. It seems like having the GB change the ISO would be at least as easy as it is to have it change the shutter speed. It obviously couldn't change the aperture on a non-a lens, but I don't think I would want it to. An option between the two would be nice.

It's a good feature as it is, where it would get me some more photos is when the subject or light changes. Let's say I'm photographing a squirrel or kid playing and I have my shutter speed and aperture where they need to be (-ish), I meter and all is good, then they move into different light and there's a moment that I want to capture. If I GB it, and there is less light, it will drop my shutter speed to some unacceptable level and I'll have to adjust ISO and shutter speed to get exposed properly then the moment is probably gone. But if the GB just raised the ISO, I'd get the shot. I can skip the GB and manually raise the ISO, but I'm guessing by how much, which is the opposite of metering.

In that same scenario if they moved into MORE light, it would be fine because faster shutter speed would not ruin the shot.

Anyway...it's a good feature and there are other lens choices for those scenarios, but I happen to be "walking around" with an M lens this week and it got me thinking about it, not for the first time, so I thought I would lament.

---------- Post added 04-01-15 at 10:05 AM ----------

Originally posted by stevebrot

Hmmmm...that would be an interesting twist, though I am not sure how it would be implemented, perhaps using the optical DOF preview and a special custom menu setting?

BTW...thanks to this question, I just discovered a previously unknown (at least to me) feature of the K-3 when using M-42 lenses. In Av mode you can switch to auto-ISO and the camera assumes a program mode with aperture floating freely and the shutter speed changing only as needed. Very cool.

Steve

I'm not sure what you mean by "Auto-ISO", but I discovered earlier this year that I'm happy shooting wide open with a non-A lens, I can set it to Av mode, set the ISO to something and then have it adjust shutter speed for me. Is that what you mean or am I missing a trick?

---------- Post added 04-01-15 at 10:12 AM ----------

Originally posted by Lowell Goudge

Implementation would be easy, today, when you stop down with green button, it measures the light through the lens, and using the ISO setting calculates shutter speed, no big deal to impose shutter speed and let it calculate the needed ISO within range of the auto ISO setting, and only if ISO would be outside the range, set the shutter speed as required, slower if ISO at maximum, faster if ISO is at minimum, to still make exposure.

...

Yeah, this is exactly what I mean. I thought about the issue of hitting limits too. If it can't stop down or up enough to get the exposure with the shutter speed and aperture I've imposed, but the same problem exists when changing shutter speed as well, though I suppose the range of SS is larger so it's inclined to happen less often. It's really another argument for enhancing this feature. If you menu select that you want it to change ISO first, within a range, then it can go to shutter speed when it hits a floor or ceiling. If you want it to work the other way, it could, just by specifying the order in a menu.

stevebrot · 04-01-2015, 10:35 AM

Originally posted by troika

I'm not sure what you mean by "Auto-ISO", but I discovered earlier this year that I'm happy shooting wide open with a non-A lens, I can set it to Av mode, set the ISO to something and then have it adjust shutter speed for me. Is that what you mean or am I missing a trick?

Auto-ISO is something to know about.

When turned on, ISO will float in a manner similar to TAv mode in all auto-exposure modes. To enable on your K-5 II, hold down the ISO button while pressing the green button. To defeat, hold down the ISO button and set the ISO using the e-dial.

In Av mode with auto-ISO on, the body will shift ISO pretty much preferential to the shutter speed unless auto-ISO is set to "slow" (see capture menu settings). The surprise is that this behavior carries over when non-A contact lenses are mounted.

Steve

Zephos · 04-01-2015, 02:46 PM - **1 Like**

Originally posted by troika

Just a thought I had, don't know if this is the right place to post and hopefully this hasn't already been discussed ad nauseam.

I use the green button frequently to meter K and M lenses. It's a good feature. What would make it better for me is if it changed ISO to get me to my desired exposure rather than shutter speed. Normally, I've chosen aperture for the photo I want, sometimes I may be willing to move it a stop or so after I meter to get to where I want to be. I usually either set the shutter speed to the slowest position that I think I can get away with for that lens (if handheld) or based on what's appropriate for what I'm shooting.

I want the ISO to be as low as possible, but for most exposures, it's the corner of the exposure triangle that I'm most flexible on, which is why I like Tav mode with A lenses. I suppose better still if I could choose which of those two things the green button changes (maybe I should check the menu to make sure I can't).

As it is, I chose an ISO that I think might be appropriate, then set aperture and shutter speed and then meter and adjust. It will change the shutter speed for me, but frequently, I change it back and then adjust ISO and maybe aperture by the corresponding number of stops and maybe or maybe don't remeter depending on what I'm shooting. If what I'm photographing is pretty consistent light-wise, it's really not a big deal once I'm dialed it.

Just ruminations. Wonder how others of you might have worked this feature.

You already have this functionality by using TaV mode with auto-ISO. Then you don't even need to press the green button because it is constantly adjusting the ISO already. It's nice because you can set a range for ISO so that it doesn't go too high. At least that's how it is on my K-50.

troika · 04-01-2015, 02:54 PM

I need to learn this Auto-ISO thing. I have my camera with me, but I didn't get it on the first try and haven't had time to research further. I'll check the manual tonight. That would be awesome!

---------- Post added 04-01-15 at 03:04 PM ----------

So, I have an SMC-M 100/4 lens mounted.

If I put it in Tav mode and push and hold the ISO and the Green Buttons, "Auto" appears next to the ISO and the ISO moves up and down as a focus on lighter and dimmer objects. Cool.

I'm at f8 and 1/125th second. The ISO settles into 400 and I get the shot.
Stop down to f5.6 and stay at 1/125th second and repeat. Auto appears next to the ISO and it flutters up and down as I focus on lighter and dimmer objects, but when I take a photo of the same thing as before, the ISO is still 400. This tells me that my aperture was actually f4 both times as it is when you have a non-a contacts lens in a mode other than M.

I can't get "auto" to appear next to ISO when it M mode using the same process. Am I doing something wrong?

stevebrot · 04-01-2015, 04:43 PM

Originally posted by Zephos

You already have this functionality by using TaV mode with auto-ISO. Then you don't even need to press the green button because it is constantly adjusting the ISO already. It's nice because you can set a range for ISO so that it doesn't go too high. At least that's how it is on my K-50.

The OP is using K and M series lenses (no electrical contacts on the base). For those lenses, operation is essentially limited to M mode and metering is done with the lens stopped down using the green button. In other than M, X, or B modes the camera defaults to Av with the aperture remaining full open. Your K-50 behaves the same way.

Steve

troika · 04-01-2015, 11:31 PM

Originally posted by stevebrot

The OP is using K and M series lenses (no electrical contacts on the base). For those lenses, operation is essentially limited to M mode and metering is done with the lens stopped down using the green button. In other than M, X, or B modes the camera defaults to Av with the aperture remaining full open. Your K-50 behaves the same way.

Steve

Thanks for the clarification. That's what I thought and it matches the experience I was having experimenting today.

r1ch13 · 07-01-2015, 12:58 PM

Originally posted by troika

Thanks for the clarification. That's what I thought and it matches the experience I was having experimenting today.

It would be really nice if Pentax could give us TAv mode with Manual Lenses. My Canon bodies can do this :-(

stevebrot · 07-01-2015, 07:12 PM

Originally posted by r1ch13

My Canon bodies can do this :-(

TAv with "manual" lenses? Are you referring to lenses where the body is unable to set the aperture? Since TAv requires that the body control all three sides of the exposure triangle, that is never going to happen with lenses lacking the proper coupling. The body must either "know" the set aperture or be in control of such to implement TAv.

As for Canon, it is my understanding that support for non-EF lenses is limited to stop-down metering in a manner essentially similar to Pentax, the main difference is that you lose auto-aperture actuation. Is there a special trick?

Steve

troika · 07-01-2015, 11:12 PM

Originally posted by stevebrot

TAv with "manual" lenses? Are you referring to lenses where the body is unable to set the aperture? Since TAv requires that the body control all three sides of the exposure triangle, that is never going to happen with lenses lacking the proper coupling. The body must either "know" the set aperture or be in control of such to implement TAv.

...

Well...I agree that that is how it works, but I'm not convinced that it has to.

In manual mode with GB metering, you set the ISO and shutter speed (and aperture, manually on the lens).

It "knows" the ISO and Shutter Speed, but doesn't "know" aperture. When we push the green button, it meters and determines that it is x-stops above or below proper exposure. It then changes the shutter speed to achieve the proper exposure value. What would been the technical problem with programing it to adjust the ISO instead?

r1ch13 · 07-02-2015, 04:39 AM

Originally posted by stevebrot

TAv with "manual" lenses? Are you referring to lenses where the body is unable to set the aperture? Since TAv requires that the body control all three sides of the exposure triangle, that is never going to happen with lenses lacking the proper coupling. The body must either "know" the set aperture or be in control of such to implement TAv.

As for Canon, it is my understanding that support for non-EF lenses is limited to stop-down metering in a manner essentially similar to Pentax, the main difference is that you lose auto-aperture actuation. Is there a special trick?

Steve

Wouldn't it be awesome though, when using old Legacy/non body controlled Aperture lenses, if we could:

1. Select the Aperture on our Manual lenses
2. Select the Shutter Speed we want

And just let the camera worry about the ISO. When we shot with film it was the ISO film roll we loaded that limited us, so we had to select the appropriate shutter and aperture to suit our roll. But with the digital bodies they are so good now ISO should no longer be limiting us.

Would be interesting to hear others thoughts on this.

(TAv mode that worked with Old Manual/Legacy non body controlled Aperture lenses)

---------- Post added 07-02-15 at 09:51 PM ----------

Originally posted by troika

Well...I agree that that is how it works, but I'm not convinced that it has to.

In manual mode with GB metering, you set the ISO and shutter speed (and aperture, manually on the lens).

It "knows" the ISO and Shutter Speed, but doesn't "know" aperture. When we push the green button, it meters and determines that it is x-stops above or below proper exposure. It then changes the shutter speed to achieve the proper exposure value. What would been the technical problem with programing it to adjust the ISO instead?

I understand what you are saying - but if you think about it, do you reckon it really needs to have the the Aperture dialed in through the body? Like why can't it just read the amount of light coming in through the lens like it does in Av mode (we already know this works with our old maunal lenses stepped down). And then combine that reading with the Shutter Speed we select - to work out the ISO for correct exposure.

just thinkin out loud...

I hope Pentax is listening ;-)

04-01-2015, 09:32 AM	#1
troika Pentaxian Join Date: Dec 2012 Location: Seattle, WA USA Posts: 1,753	Green Button Metering Wish Just a thought I had, don't know if this is the right place to post and hopefully this hasn't already been discussed ad nauseam. I use the green button frequently to meter K and M lenses. It's a good feature. What would make it better for me is if it changed ISO to get me to my desired exposure rather than shutter speed. Normally, I've chosen aperture for the photo I want, sometimes I may be willing to move it a stop or so after I meter to get to where I want to be. I usually either set the shutter speed to the slowest position that I think I can get away with for that lens (if handheld) or based on what's appropriate for what I'm shooting. I want the ISO to be as low as possible, but for most exposures, it's the corner of the exposure triangle that I'm most flexible on, which is why I like Tav mode with A lenses. I suppose better still if I could choose which of those two things the green button changes (maybe I should check the menu to make sure I can't). As it is, I chose an ISO that I think might be appropriate, then set aperture and shutter speed and then meter and adjust. It will change the shutter speed for me, but frequently, I change it back and then adjust ISO and maybe aperture by the corresponding number of stops and maybe or maybe don't remeter depending on what I'm shooting. If what I'm photographing is pretty consistent light-wise, it's really not a big deal once I'm dialed it. Just ruminations. Wonder how others of you might have worked this feature.

04-01-2015, 09:43 AM	#3
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	I usually approach this by setting the ISO first, in the ball park, of where I know I'll need to be for conditions. Then set aperture for creative reasons and then meter for the shutter speed. But I can see the reasoning behind your idea. It would not be impossible to implement then have green button button metering configurable in the menu to which of the three you want to change. But I suspect that would be low on the do to list for Ricoh. Not many new lenses made that require stop down metering.

04-01-2015, 10:01 AM	#6
troika Pentaxian Join Date: Dec 2012 Location: Seattle, WA USA Posts: 1,753 Original Poster	Originally posted by jatrax ... But I suspect that would be low on the do to list for Ricoh. Not many new lenses made that require stop down metering. I just scrolled through the menu function to make sure I wasn't missing a setting, but I don't see anything. Yes, I expect it is low on the feature list for the reasons you said, but one of the great things about Pentax is how far they've come to enable backward compatibility to old lenses. It seems like having the GB change the ISO would be at least as easy as it is to have it change the shutter speed. It obviously couldn't change the aperture on a non-a lens, but I don't think I would want it to. An option between the two would be nice. It's a good feature as it is, where it would get me some more photos is when the subject or light changes. Let's say I'm photographing a squirrel or kid playing and I have my shutter speed and aperture where they need to be (-ish), I meter and all is good, then they move into different light and there's a moment that I want to capture. If I GB it, and there is less light, it will drop my shutter speed to some unacceptable level and I'll have to adjust ISO and shutter speed to get exposed properly then the moment is probably gone. But if the GB just raised the ISO, I'd get the shot. I can skip the GB and manually raise the ISO, but I'm guessing by how much, which is the opposite of metering. In that same scenario if they moved into MORE light, it would be fine because faster shutter speed would not ruin the shot. Anyway...it's a good feature and there are other lens choices for those scenarios, but I happen to be "walking around" with an M lens this week and it got me thinking about it, not for the first time, so I thought I would lament. ---------- Post added 04-01-15 at 10:05 AM ---------- Originally posted by stevebrot Hmmmm...that would be an interesting twist, though I am not sure how it would be implemented, perhaps using the optical DOF preview and a special custom menu setting? BTW...thanks to this question, I just discovered a previously unknown (at least to me) feature of the K-3 when using M-42 lenses. In Av mode you can switch to auto-ISO and the camera assumes a program mode with aperture floating freely and the shutter speed changing only as needed. Very cool. Steve I'm not sure what you mean by "Auto-ISO", but I discovered earlier this year that I'm happy shooting wide open with a non-A lens, I can set it to Av mode, set the ISO to something and then have it adjust shutter speed for me. Is that what you mean or am I missing a trick? ---------- Post added 04-01-15 at 10:12 AM ---------- Originally posted by Lowell Goudge Implementation would be easy, today, when you stop down with green button, it measures the light through the lens, and using the ISO setting calculates shutter speed, no big deal to impose shutter speed and let it calculate the needed ISO within range of the auto ISO setting, and only if ISO would be outside the range, set the shutter speed as required, slower if ISO at maximum, faster if ISO is at minimum, to still make exposure. ... Yeah, this is exactly what I mean. I thought about the issue of hitting limits too. If it can't stop down or up enough to get the exposure with the shutter speed and aperture I've imposed, but the same problem exists when changing shutter speed as well, though I suppose the range of SS is larger so it's inclined to happen less often. It's really another argument for enhancing this feature. If you menu select that you want it to change ISO first, within a range, then it can go to shutter speed when it hits a floor or ceiling. If you want it to work the other way, it could, just by specifying the order in a menu. Last edited by troika; 04-01-2015 at 11:01 AM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Stop Down Metering With The Green Button: Wrong Exposure Recomendations	Obs	Troubleshooting and Beginner Help	55	03-27-2015 09:39 AM
K50 Screwmount Metering Issues: Green Button Meters in LV but not in VF	Relativity	Pentax K-30 & K-50	5	01-31-2014 10:17 AM
metering with green button	GUB	Pentax K-30 & K-50	6	12-24-2012 02:47 AM
Green Button Stop-Down Metering Acting Differently	woefulwabbit	Pentax DSLR Discussion	22	03-29-2011 09:56 PM
Green Button Metering with Manual Lens	zombieCat	Pentax DSLR Discussion	4	02-15-2010 06:07 AM

04-01-2015, 09:34 AM	#2
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,886	I don't know about all cameras, but in manual mode, there is no auto ISO. I understand the objective though. Many times you can have the shutter speed get set far too low, for the subject when aperture is fixed,

04-01-2015, 09:49 AM	#4
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by troika I use the green button frequently to meter K and M lenses. It's a good feature. What would make it better for me is if it changed ISO to get me to my desired exposure rather than shutter speed. Hmmmm...that would be an interesting twist, though I am not sure how it would be implemented, perhaps using the optical DOF preview and a special custom menu setting? BTW...thanks to this question, I just discovered a previously unknown (at least to me) feature of the K-3 when using M-42 lenses. In Av mode you can switch to auto-ISO and the camera assumes a program mode with aperture floating freely and the shutter speed changing only as needed. Very cool. Steve

04-01-2015, 09:54 AM	#5
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,886	Originally posted by stevebrot Hmmmm...that would be an interesting twist, though I am not sure how it would be implemented, perhaps using the optical DOF preview and a special custom menu setting? BTW...thanks to this question, I just discovered a previously unknown (at least to me) feature of the K-3 when using M-42 lenses. In Av mode you can switch to auto-ISO and the camera assumes a program mode with aperture floating freely and the shutter speed changing only as needed. Very cool. Steve Implementation would be easy, today, when you stop down with green button, it measures the light through the lens, and using the ISO setting calculates shutter speed, no big deal to impose shutter speed and let it calculate the needed ISO within range of the auto ISO setting, and only if ISO would be outside the range, set the shutter speed as required, slower if ISO at maximum, faster if ISO is at minimum, to still make exposure. As for the use of AV mode and auto ISO this is how I shoot most of the time with M42 lenses. It is a sort of TAV mode Note that the Q allows auto ISO in manual

04-01-2015, 10:35 AM	#7
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by troika I'm not sure what you mean by "Auto-ISO", but I discovered earlier this year that I'm happy shooting wide open with a non-A lens, I can set it to Av mode, set the ISO to something and then have it adjust shutter speed for me. Is that what you mean or am I missing a trick? Auto-ISO is something to know about. When turned on, ISO will float in a manner similar to TAv mode in all auto-exposure modes. To enable on your K-5 II, hold down the ISO button while pressing the green button. To defeat, hold down the ISO button and set the ISO using the e-dial. In Av mode with auto-ISO on, the body will shift ISO pretty much preferential to the shutter speed unless auto-ISO is set to "slow" (see capture menu settings). The surprise is that this behavior carries over when non-A contact lenses are mounted. Steve

04-01-2015, 02:46 PM - 1 Like	#8
Zephos Veteran Member Join Date: Jan 2015 Location: Salt Lake City, Utah Photos: Albums Posts: 341	Originally posted by troika Just a thought I had, don't know if this is the right place to post and hopefully this hasn't already been discussed ad nauseam. I use the green button frequently to meter K and M lenses. It's a good feature. What would make it better for me is if it changed ISO to get me to my desired exposure rather than shutter speed. Normally, I've chosen aperture for the photo I want, sometimes I may be willing to move it a stop or so after I meter to get to where I want to be. I usually either set the shutter speed to the slowest position that I think I can get away with for that lens (if handheld) or based on what's appropriate for what I'm shooting. I want the ISO to be as low as possible, but for most exposures, it's the corner of the exposure triangle that I'm most flexible on, which is why I like Tav mode with A lenses. I suppose better still if I could choose which of those two things the green button changes (maybe I should check the menu to make sure I can't). As it is, I chose an ISO that I think might be appropriate, then set aperture and shutter speed and then meter and adjust. It will change the shutter speed for me, but frequently, I change it back and then adjust ISO and maybe aperture by the corresponding number of stops and maybe or maybe don't remeter depending on what I'm shooting. If what I'm photographing is pretty consistent light-wise, it's really not a big deal once I'm dialed it. Just ruminations. Wonder how others of you might have worked this feature. You already have this functionality by using TaV mode with auto-ISO. Then you don't even need to press the green button because it is constantly adjusting the ISO already. It's nice because you can set a range for ISO so that it doesn't go too high. At least that's how it is on my K-50.

04-01-2015, 02:54 PM	#9
troika Pentaxian Join Date: Dec 2012 Location: Seattle, WA USA Posts: 1,753 Original Poster	I need to learn this Auto-ISO thing. I have my camera with me, but I didn't get it on the first try and haven't had time to research further. I'll check the manual tonight. That would be awesome! ---------- Post added 04-01-15 at 03:04 PM ---------- So, I have an SMC-M 100/4 lens mounted. If I put it in Tav mode and push and hold the ISO and the Green Buttons, "Auto" appears next to the ISO and the ISO moves up and down as a focus on lighter and dimmer objects. Cool. I'm at f8 and 1/125th second. The ISO settles into 400 and I get the shot. Stop down to f5.6 and stay at 1/125th second and repeat. Auto appears next to the ISO and it flutters up and down as I focus on lighter and dimmer objects, but when I take a photo of the same thing as before, the ISO is still 400. This tells me that my aperture was actually f4 both times as it is when you have a non-a contacts lens in a mode other than M. I can't get "auto" to appear next to ISO when it M mode using the same process. Am I doing something wrong?

04-01-2015, 04:43 PM	#10
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by Zephos You already have this functionality by using TaV mode with auto-ISO. Then you don't even need to press the green button because it is constantly adjusting the ISO already. It's nice because you can set a range for ISO so that it doesn't go too high. At least that's how it is on my K-50. The OP is using K and M series lenses (no electrical contacts on the base). For those lenses, operation is essentially limited to M mode and metering is done with the lens stopped down using the green button. In other than M, X, or B modes the camera defaults to Av with the aperture remaining full open. Your K-50 behaves the same way. Steve

04-01-2015, 11:31 PM	#11
troika Pentaxian Join Date: Dec 2012 Location: Seattle, WA USA Posts: 1,753 Original Poster	Originally posted by stevebrot The OP is using K and M series lenses (no electrical contacts on the base). For those lenses, operation is essentially limited to M mode and metering is done with the lens stopped down using the green button. In other than M, X, or B modes the camera defaults to Av with the aperture remaining full open. Your K-50 behaves the same way. Steve Thanks for the clarification. That's what I thought and it matches the experience I was having experimenting today.

07-01-2015, 12:58 PM	#12
r1ch13 New Member Join Date: Aug 2012 Photos: Gallery \| Albums Posts: 12	Originally posted by troika Thanks for the clarification. That's what I thought and it matches the experience I was having experimenting today. It would be really nice if Pentax could give us TAv mode with Manual Lenses. My Canon bodies can do this :-(

07-01-2015, 07:12 PM	#13
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by r1ch13 My Canon bodies can do this :-( TAv with "manual" lenses? Are you referring to lenses where the body is unable to set the aperture? Since TAv requires that the body control all three sides of the exposure triangle, that is never going to happen with lenses lacking the proper coupling. The body must either "know" the set aperture or be in control of such to implement TAv. As for Canon, it is my understanding that support for non-EF lenses is limited to stop-down metering in a manner essentially similar to Pentax, the main difference is that you lose auto-aperture actuation. Is there a special trick? Steve

Thread Tools	Search this Thread
	Search this Thread: Advanced Search

07-01-2015, 11:12 PM	#14
troika Pentaxian Join Date: Dec 2012 Location: Seattle, WA USA Posts: 1,753 Original Poster	Originally posted by stevebrot TAv with "manual" lenses? Are you referring to lenses where the body is unable to set the aperture? Since TAv requires that the body control all three sides of the exposure triangle, that is never going to happen with lenses lacking the proper coupling. The body must either "know" the set aperture or be in control of such to implement TAv. ... Well...I agree that that is how it works, but I'm not convinced that it has to. In manual mode with GB metering, you set the ISO and shutter speed (and aperture, manually on the lens). It "knows" the ISO and Shutter Speed, but doesn't "know" aperture. When we push the green button, it meters and determines that it is x-stops above or below proper exposure. It then changes the shutter speed to achieve the proper exposure value. What would been the technical problem with programing it to adjust the ISO instead?

07-02-2015, 04:39 AM	#15
r1ch13 New Member Join Date: Aug 2012 Photos: Gallery \| Albums Posts: 12	Originally posted by stevebrot TAv with "manual" lenses? Are you referring to lenses where the body is unable to set the aperture? Since TAv requires that the body control all three sides of the exposure triangle, that is never going to happen with lenses lacking the proper coupling. The body must either "know" the set aperture or be in control of such to implement TAv. As for Canon, it is my understanding that support for non-EF lenses is limited to stop-down metering in a manner essentially similar to Pentax, the main difference is that you lose auto-aperture actuation. Is there a special trick? Steve Wouldn't it be awesome though, when using old Legacy/non body controlled Aperture lenses, if we could: 1. Select the Aperture on our Manual lenses 2. Select the Shutter Speed we want And just let the camera worry about the ISO. When we shot with film it was the ISO film roll we loaded that limited us, so we had to select the appropriate shutter and aperture to suit our roll. But with the digital bodies they are so good now ISO should no longer be limiting us. Would be interesting to hear others thoughts on this. (TAv mode that worked with Old Manual/Legacy non body controlled Aperture lenses) ---------- Post added 07-02-15 at 09:51 PM ---------- Originally posted by troika Well...I agree that that is how it works, but I'm not convinced that it has to. In manual mode with GB metering, you set the ISO and shutter speed (and aperture, manually on the lens). It "knows" the ISO and Shutter Speed, but doesn't "know" aperture. When we push the green button, it meters and determines that it is x-stops above or below proper exposure. It then changes the shutter speed to achieve the proper exposure value. What would been the technical problem with programing it to adjust the ISO instead? I understand what you are saying - but if you think about it, do you reckon it really needs to have the the Aperture dialed in through the body? Like why can't it just read the amount of light coming in through the lens like it does in Av mode (we already know this works with our old maunal lenses stepped down). And then combine that reading with the Shutter Speed we select - to work out the ISO for correct exposure. just thinkin out loud... I hope Pentax is listening ;-)