[Raybo]

OK,

Somebody please correct me if i'm wrong.

I thought SR worked by keeping the image centered on the sensor, there for the reason the camera needs to know the FL (the sensor than moves accordingly). I "don't" think SR has anything to do with shutter speed.

[RuiC]

Wow... can you read? I will try to break it down for you.

I know how exposure works. Probably more than most people, down to the bits of light and logarithmic stops - I am a theory person.

Since on a DSLR, it has the ability to control ISO automatically, it intelligently selects a shutter speed based on the focal length for hand shake purposes, varying the ISO to obtain it (if in Av mode). In Sv and Pv mode, it also selects a shutter speed based on the focal length. The lens digitally communicates with the digital SLR to tell it which focal length the lens is at. This information is even stored into the EXIF data. The camera needs to know a goal of what shutter speed to select because today, there are 3 variables it can control by itself, when there only used to be 2. Since there is an extra variable, cameras now need to know what to aim at for one of the variables. This could be a shutter speed that will acceptably bypass handshaking, an aperture that has a max MTF, or an ISO that has an acceptable amount of noise.

The next part I am getting a little nit-picky about the camera communication, feel free to not read this if you do not understand how it works. No I am not referring to variable aperture zooms, because in no way does the camera really know the true aperture. It would actually be digitally impossible to communicate the exact aperture of a variable aperture zoom, you could only get it accurate to a certain precision. What is told, instead, is the fraction of light that will be received compared to wide open. The f/number you see in the camera on these digital lenses is fake and not even used to determine the final exposure. In fact, no lenses transmit their exact true f-number, just what fraction of light is expected to be received by the sensor or film. This is because aperture is a ratio of lengths that can never be exact, so they are approximate. Even if lenses could transmit the exact f-number, it would be absolutely pointless because each lens, through design or even manufacture tolerances, robs light a different amount before it gets to the sensor.

This doesn't matter to a camera because it doesn't need to know the aperture, it just needs to know the light it will receive. Thus, the 3 things that really determine exposure is the rate of light coming in (determined as a fraction of the light currently coming in), length of light coming in (shutter), and amplification of light (ISO).

So please don't explain the basics in my thread in a condescending matter, incorrectly assuming I don't know anything about photography. This isn't the beginner's corner.

Well, to begin with I am not condescending. I am mad about this.

2nd: It is true this isn't a beginner's corner. But this isn't the Futuristic Camera's corner either. That what you need is a DSLR with FL mode in addition to Sv, Tv, Av, P, B, X, Y, Z modes.

3rd: The camera knows what aperture the lens is set to. Put a 50-200 on it. Pull to 50mm and it says F4 push to 200mm it says F5.6. Now What? Your M42 lens communicates the FL to the body, is it correct? Which pins on the body are used to do that? I am confused now. Congratulations on that.

Enjoy your camera. Take photos.

Over and Out.
AR SK

Rui

[Lowell Goudge]

"far beyond minimum functionality"? That's an interesting use of terms. I guess its always good to be somewhat beyond the minimum, no?

I personally believe it's beyond what is expected with manual lenses, but was led to believe that it was implemented as such and had different expectations.

A better approach would have been to disable auto-ISO altogether with manual lenses. Don't include a feature if it isn't implemented correctly.

what I mean to say is that generally the approach taken is to give the functionality that duplicates what the lenses could do on the cameras they were initially intended to be used on, within the limits of mechanical linkages (or lack thereof)

while I agree that what you propose is interesting in concept, what pentax already offers is so far in advance of other manufactures. isn't it already enough? for cannon there is no upgrade at all, and for nikon, only the pro cameras give any form of control, all others simpl;y let you guess at the metering.

also what led you to believe this was implemented in this way?

[Nesster]

Several of us have used M42 lenses in Av mode for thousands of photos. If the answers and suggestions above have not been satisfactory, please don't get huffy. If we have not encountered the same problem as you, please excuse us.

For me the basic mystery of your question comes down to: why does the camera stick to 1/125 shutter (and the other one to 1/90)? This does not happen with my K100D nor does it happen AFAIK with any other recent model. The most reasonable reason for such behavior: you have the pop up flash up, and the camera is working with flash sync.

The camera has no way of communicating electronically with the lens. With modern K mounts, yes, and it can take FL etc into consideration. But with M42, the camera cannot make any assumptions at all. It is as though you had a single-aperture lens, eg. a mirror, on. So you are right about that part - the light it sees is the light it assumes it will get at exposure time. No auto aperture.

Whether auto ASA or no, my camera will assign shutter speed and adjust ASA with whatever is programmed in. However, as I always need to dial in exposure comp, that defeats auto ASA, so I tend to set mine manually to 400 anyway.

Now, perhaps Pentax could trust the photographer's input for SR for focal length in its calculations. In fact that might be a good idea.

The thing about using M42 glass for most of us is that it gets us AWAY from most of the automated gizmos, it brings back a tiny bit of manually intensive photography, and some usage of brains. Most of us don't mind the lack of multi-segmented multi-line automated exposure - we prefer to understand when something is back-lit. So if I understand the OP correctly, wondering about these things has not occurred to most of us.

But I am mystified about the 'stuck' shutter speed. Please can you describe it better- it ALWAYS happens when you mount ANY M42, did I understand that correctly? Like I say above, the only thing I can come up with is flash sync speed.

OK, I read more carefully - you say the camera wants to stick to 1/125 when you are in Auto ISO. Only when it reaches the Auto ISO limits does it start to move the shutter speed. That is interesting, and could even be useful. For my set up (which I don't even have any longer as my daughter took the K100D) as I said, I always have to dial in exposure comp, which would default auto ISO to 200 due to another Pentax boner. So I usually do not shoot in auto ISO, and thus have not experienced this.

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Last edited by Nesster; 11-28-2009 at 03:00 PM.

[Mike Cash]

Wow... can you read? I will try to break it down for you.

I know how exposure works. Probably more than most people, down to the bits of light and logarithmic stops - I am a theory person.

From your bellicosity we had already pretty much figured out you're not a people person. Some have probably even privately remarked to themselves on how appropriate the last three letters of your user name are.

I get what you're driving at and agree that it would be nice if Pentax would implement some sort of option for holding the shutter speed at or above 1/f when using auto ISO with M42 lenses. I'll never understand why you don't just use the simple expedient of limiting your auto range to something sensible, though. To me there appears a contradiction between being so uptight over one variable (shutter) and being content to use any setting on another (ISO). But that's none of my business, so you needn't bother explaining it to me.

The problem is twofold:

1. M42 users are red-headed stepchildren as far as the folks who develop Pentax cameras are concerned. They do the minimum to keep us fed and that's about it. In other words, I doubt the issue ever once crossed their minds.

2. You can't please everybody. Just as sure as they implement a "fix" to get the shutter speed where you want it, somebody else will pop up and b*tch about the shutter speed now being too fast/slow for their purposes.

You're already manually focusing, manually stopping down the aperture.....is it so onerous a burden to have to choose an ISO?

In Av mode I keep my rear wheel set to select ISO. Works great for controlling the shutter speed. And though I rarely use it, I have the green button set to return the ISO to auto. The main way I use it is to set auto to a very narrow range, then if I have had to dial up a much higher ISO for a particular shot and need to quickly get back down to where I was all I have to do is hit the button. The only change I wish they would implement is in the custom set-up menu to allow us to choose to have EV compensation on one of the two e-wheels. I'd love to have EV compensation on my front wheel where I could quickly and easily use it to adjust for backlighting instead of the awkward method that we have now.

[Lowell Goudge]

Several of us have used M42 lenses in Av mode for thousands of photos. If the answers and suggestions above have not been satisfactory, please don't get huffy. If we have not encountered the same problem as you, please excuse us.

For me the basic mystery of your question comes down to: why does the camera stick to 1/125 shutter (and the other one to 1/90)? This does not happen with my K100D nor does it happen AFAIK with any other recent model. The most reasonable reason for such behavior: you have the pop up flash up, and the camera is working with flash sync.

just to add some clarity, I tried this with my K7 and an ae lens (vivitar 85mm F1.4 in KA mount) it does the same thing. It is just like in flash mode with auto iso, it tries for correct exposure with ISO before adjusting flash, so shots are set to maximim ISO every time

The camera has no way of communicating electronically with the lens. With modern K mounts, yes, and it can take FL etc into consideration. But with M42, the camera cannot make any assumptions at all. It is as though you had a single-aperture lens, eg. a mirror, on. So you are right about that part - the light it sees is the light it assumes it will get at exposure time. No auto aperture.

No it does not communicate but you do enter FL for shake reduction, it is just that this is not linked to the auto iso function

Whether auto ASA or no, my camera will assign shutter speed and adjust ASA with whatever is programmed in. However, as I always need to dial in exposure comp, that defeats auto ASA, so I tend to set mine manually to 400 anyway.

Now, perhaps Pentax could trust the photographer's input for SR for focal length in its calculations. In fact that might be a good idea.

The thing about using M42 glass for most of us is that it gets us AWAY from most of the automated gizmos, it brings back a tiny bit of manually intensive photography, and some usage of brains. Most of us don't mind the lack of multi-segmented multi-line automated exposure - we prefer to understand when something is back-lit. So if I understand the OP correctly, wondering about these things has not occurred to most of us.

But I am mystified about the 'stuck' shutter speed. Please can you describe it better- it ALWAYS happens when you mount ANY M42, did I understand that correctly? Like I say above, the only thing I can come up with is flash sync speed.

OK, I read more carefully - you say the camera wants to stick to 1/125 when you are in Auto ISO. Only when it reaches the Auto ISO limits does it start to move the shutter speed. That is interesting, and could even be useful. For my set up (which I don't even have any longer as my daughter took the K100D) as I said, I always have to dial in exposure comp, which would default auto ISO to 200 due to another Pentax boner. So I usually do not shoot in auto ISO, and thus have not experienced this.

note I suspect the variability of shutter speed is due to the ISO/EV steps selected

[Eruditass]

From your bellicosity we had already pretty much figured out you're not a people person. Some have probably even privately remarked to themselves on how appropriate the last three letters of your user name are.

I'd be surprised if you could figure out the real meaning of my name.

But to keep you from staying up at night, it is actually "erudite + ass." Feel free to grab a dictionary. Well, I'll save you again, it is a "smart" way of saying "smart ass"! Befitting, isn't it?

and congratulations on getting half of it!

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Last edited by Eruditass; 11-30-2009 at 10:06 AM.

[Eruditass]

Well, to begin with I am not condescending. I am mad about this.

2nd: It is true this isn't a beginner's corner. But this isn't the Futuristic Camera's corner either. That what you need is a DSLR with FL mode in addition to Sv, Tv, Av, P, B, X, Y, Z modes.

3rd: The camera knows what aperture the lens is set to. Put a 50-200 on it. Pull to 50mm and it says F4 push to 200mm it says F5.6. Now What? Your M42 lens communicates the FL to the body, is it correct? Which pins on the body are used to do that? I am confused now. Congratulations on that.

Some people become condescending whether they like it or not when they are mad. I'm sure I have come across this way

Try reading again.. FL is incorporated into Sv, Av, P, but not Tv, B, X, Y, and Z modes.

It will be F4 and F5.6 at two infinitesimally small instants as you rotate the barrel. The rest are inaccurate and not "true" aperture. In addition, even fixed aperture or fixed focal length lenses don't report a 100% accurate apertures due to precision error and mechanical tolerances. It is unimportant for a camera to know the true aperture, and much more practical to combine that with the transmission properties of the glass and optical design to take the light currently coming in, and the amount that it will come in when taking a picture. Maybe a little too theoretical for you and certainly out of the scope of this thread. Feel free to PM me if you have any trouble with this.

Read all that I had wrote, you'd have discerned I said "when I enter the focal length in the body."
As for taking photos, I am trying to, but there is too much misunderstanding in this thread!

[Eruditass]

I get what you're driving at and agree that it would be nice if Pentax would implement some sort of option for holding the shutter speed at or above 1/f when using auto ISO with M42 lenses. I'll never understand why you don't just use the simple expedient of limiting your auto range to something sensible, though. To me there appears a contradiction between being so uptight over one variable (shutter) and being content to use any setting on another (ISO). But that's none of my business, so you needn't bother explaining it to me.

There is no reason to limit the auto-ISO if it doesn't pay attention to the focal length. Thus, it is more practical to disable Auto-ISO altogether - which is what I do and have been doing. I only made this thread because I was wondering if it was meant to be like this, not that I am stuck in auto-iso and can't take sensible pictures, or don't understand exposure.

My main complaint is that auto-ISO is available. If it isn't implemented properly, it shouldn't be enabled.

The problem is twofold:
1. M42 users are red-headed stepchildren as far as the folks who develop Pentax cameras are concerned. They do the minimum to keep us fed and that's about it. In other words, I doubt the issue ever once crossed their minds.

I suspected this and am content - I am not bashing Pentax for not including this feature.

2. You can't please everybody. Just as sure as they implement a "fix" to get the shutter speed where you want it, somebody else will pop up and b*tch about the shutter speed now being too fast/slow for their purposes.
You're already manually focusing, manually stopping down the aperture.....is it so onerous a burden to have to choose an ISO?

Not once did I complain about it, only did I say Av auto-ISO is dumb.

In Av mode I keep my rear wheel set to select ISO. Works great for controlling the shutter speed. And though I rarely use it, I have the green button set to return the ISO to auto. The main way I use it is to set auto to a very narrow range, then if I have had to dial up a much higher ISO for a particular shot and need to quickly get back down to where I was all I have to do is hit the button. The only change I wish they would implement is in the custom set-up menu to allow us to choose to have EV compensation on one of the two e-wheels. I'd love to have EV compensation on my front wheel where I could quickly and easily use it to adjust for backlighting instead of the awkward method that we have now.

In the least, I have requested that the e-dial be made to directly change ISO, right now it does nothing.

In practice, I do limit my auto-ISO for noise purposes, but I put it at the max for purposes of testing.

[Eruditass]

Several of us have used M42 lenses in Av mode for thousands of photos. If the answers and suggestions above have not been satisfactory, please don't get huffy. If we have not encountered the same problem as you, please excuse us.

My "huffyness" is not from those not encountering the same problem, but assuming I don't know shit about photography and exposure. Then from saying I understand these things, I get "corrected" about exposure. Huffyness ensues.

For me the basic mystery of your question comes down to: why does the camera stick to 1/125 shutter (and the other one to 1/90)? This does not happen with my K100D nor does it happen AFAIK with any other recent model. The most reasonable reason for such behavior: you have the pop up flash up, and the camera is working with flash sync.

Many people have said they experience the same thing and I have my answer, but it appears some people are still confused about either this thread or some concepts I have enlightened them on.

[Eruditass]

OK,
Somebody please correct me if i'm wrong.
I thought SR worked by keeping the image centered on the sensor, there for the reason the camera needs to know the FL (the sensor than moves accordingly). I "don't" think SR has anything to do with shutter speed.

Me, me! I'll correct you!

Well, actually, you are correct in everything you have said! The only point in the thread I made about SR is that the FL is needed for SR, thus the camera knows the FL, thus the camera can use this data for choosing an intelligent shutter speed instead of picking one out of a pile randomly.

I think people are actually coming to understand the questions raised in this thread. That must be record time for me!