EV Comp in Manual Mode

NeverSatisfied · 01-11-2009, 09:55 PM

I noticed that with the K20D you can now adjust EV Comp in manual mode, which was formerly not available with the K10D. But what would be the purpose? Isn't it just as easy, if you're in manual, to adjust aperture, shutter speed, or ISO as needed? And what does the camera exactly do, if you adjust EV in manual- change ISO? It seems that you could probably use it to artificially boost ISO for extreme low-light use, but other than that, does anyone adjust EV in manual mode, and if so, why?

BBear · 01-11-2009, 10:31 PM

interesting, i never used the K20D so i am not sure how this feature works... could it be that it simply offsets the zero point?

does the manual say something about this or could you test it yourself?

And another note, i dont see how the camera will set ISO for you if it is in M mode..

blende8 · 01-12-2009, 12:08 AM

Very good!
This is useful when you use the Green Button for getting the correct exposure.
Some lenses, and some split-image screens, need a constant correction.

NeverSatisfied · 01-12-2009, 05:04 AM

Well for one thing, once you set any amount of EV comp, that adjustment remains until you physically reset it- even if you shut the camera off in between. I found that out the hard way yesterday at the park on an overcast day. I had +2 EV set (just messing around the night before), failed to notice, then wondered why I had to use ISO 800 to get a proper exposure. Took a minute to figure out.

The reason I suggested the ISO shift was because if you're in Tv or Av mode, that's all it does is adjust the opposite value (which is not always desirable). And so if you're in M where YOU set shutter and aperture specifically, what is there left for the camera to adjust?

Here's what the manual says:
"EV Compensation for M (Hyper-manual) and X (Flash X-sync speed)
For example, if the EV compensation value is set to +1.5 for M and X, an underexposure of 1.5 EV is displayed on the EV bar. if you set the exposure value so that the l is displayed at the center of the EV bar, the image will be captured with the compensated value."

The thing that confuses me is how they say setting a POSITIVE number for EV comp actually results in UNDER-exposure, and vice versa. But then I've heard people on this forum say that with certain lenses they always dial in +.3 or +.7 EV comp due to a tendency of the camera to underexpose. Aren't these two ideas in conflict with each other? Or does Pentax just not know how to explain it?

Gimbal · 01-12-2009, 05:19 AM

Originally Posted by NeverSatisfied

Here's what the manual says:
"EV Compensation for M (Hyper-manual) and X (Flash X-sync speed)
For example, if the EV compensation value is set to +1.5 for M and X, an underexposure of 1.5 EV is displayed on the EV bar. if you set the exposure value so that the l is displayed at the center of the EV bar, the image will be captured with the compensated value."

The thing that confuses me is how they say setting a POSITIVE number for EV comp actually results in UNDER-exposure, and vice versa. But then I've heard people on this forum say that with certain lenses they always dial in +.3 or +.7 EV comp due to a tendency of the camera to underexpose. Aren't these two ideas in conflict with each other? Or does Pentax just not know how to explain it?

It’s the explanation. If you have correct exposure and dial in +1, the EV-meter will change and show that the scene now is underexposed. And thus you will have to change the shutter or aperture to get the correct (+1 exposure).

alohadave · 01-12-2009, 05:22 AM

Originally Posted by NeverSatisfied

Well for one thing, once you set any amount of EV comp, that adjustment remains until you physically reset it- even if you shut the camera off in between. I found that out the hard way yesterday at the park on an overcast day. I had +2 EV set (just messing around the night before), failed to notice, then wondered why I had to use ISO 800 to get a proper exposure. Took a minute to figure out.

That would have given you a 4 stop over exposure (assuming ISO 200 as your base, 5 stops with ISO 100 as your base).

The thing that confuses me is how they say setting a POSITIVE number for EV comp actually results in UNDER-exposure, and vice versa. But then I've heard people on this forum say that with certain lenses they always dial in +.3 or +.7 EV comp due to a tendency of the camera to underexpose. Aren't these two ideas in conflict with each other? Or does Pentax just not know how to explain it?

That's not how it works. EV+ increases the exposure to allow more light. EV- lets less light in. When you are shooting snow, you dial in EV+ to brighten the snow to avoid the snow being gray. When shooting black, you dial in EV- to darken the item to avoid the black being gray.

Lowell Goudge · 01-12-2009, 05:38 AM

Originally Posted by NeverSatisfied

I noticed that with the K20D you can now adjust EV Comp in manual mode, which was formerly not available with the K10D. But what would be the purpose? Isn't it just as easy, if you're in manual, to adjust aperture, shutter speed, or ISO as needed? And what does the camera exactly do, if you adjust EV in manual- change ISO? It seems that you could probably use it to artificially boost ISO for extreme low-light use, but other than that, does anyone adjust EV in manual mode, and if so, why?

This is an extremely useful function for manual shooters, and is sadly missed on the K10D. My *istD allows for EV compensation also.

The use, for example if you deliberately want to have a specific under / over exposure, for many shots, and the light is changing, you don't want to continually check the metering, but just press for example the green button and set the exposure.

More to the point, on the K10D and K20D there are exposure errors with manual lenses and also when you attach teleconverters, because the viewing screen on these cameras specifically introduce an error in exposure that is a function of lens maximum apature, the camera reads lens apature directly through the TC and as a result, does not apply the correct compensation when the TC is attached. For my sigma 70-200 F2.8 this is a 1.3 stop error with a 2x TC.

Manual lenses have horribly non linear exposure on the K10D and K20D bodies, but if you are stopping down below FG5.6 you can accomodate for this by simply under exposing by about 1 stop.

On my *istD my M42 35mm F2 has a constant error of 1 stop (under exposing) and I simply add 1 stop with compensation ang don't have to worry about it again. Why should I have to think to that detail with every metered shot?

NeverSatisfied · 01-12-2009, 08:21 AM

"That's not how it works. EV+ increases the exposure to allow more light. EV- lets less light in. When you are shooting snow, you dial in EV+ to brighten the snow to avoid the snow being gray. When shooting black, you dial in EV- to darken the item to avoid the black being gray."
OK, that was my understanding. Thanks!

Lowell, your reference to using the green button in changing light: is that -along with- using EV comp? I use M mode mostly, and use the green button a lot. So it sounds like you'd quickly get the "proper" exposure with the green button, but meanwhile the EV comp setting you'd already chosen remains constant, the result would be the desired amount of over- or under-exposure. Correct?

Glad you said that about using TCs. I remember using the 1.4 TC on my 50-135, and having to use EV comp to get the right exposure.

I can almost see EV comp being more useful in M mode, than in Av or Tv- after all, as far as the latter two modes are concerned (and as I just learned last night), all the camera is going to do with your EV setting is adjust the opposite value accordingly. At least in M you would still have complete control over your shutter and aperture settings. Or am I still missing something?

Interesting point about using older manual lenses, good to know.

BBear · 01-12-2009, 11:54 AM

Originally Posted by NeverSatisfied

The thing that confuses me is how they say setting a POSITIVE number for EV comp actually results in UNDER-exposure, and vice versa.

It seems to me that it basically offsets the ZERO point, but obviously it is still at the center, so if you set EV+1, and it was zeroed in to begin with, it will show -1, then you adjust the exposure (either ISO, TV or AV) to get back to zero point, which in reality, it will be EV +1.

It does make sense how it works, but I am not sure how this could be better than consciously being aware that you are shooting EV+1... and like someone mentioned, if you do set this thing other than zeroed and forget to set it back, i guess it could be trouble...

Big Dave · 01-12-2009, 01:19 PM

This is a great feature. It is needed when shooting with any of the "M" type lenses to compensate for exposure differences with the older manual lenses. It is just another reason for getting a K20D instead of the K10D bargains out there.

Dave

Originally Posted by blende8

Very good!
This is useful when you use the Green Button for getting the correct exposure.
Some lenses, and some split-image screens, need a constant correction.

Lowell Goudge · 01-12-2009, 01:21 PM

Originally Posted by NeverSatisfied

Lowell, your reference to using the green button in changing light: is that -along with- using EV comp? I use M mode mostly, and use the green button a lot. So it sounds like you'd quickly get the "proper" exposure with the green button, but meanwhile the EV comp setting you'd already chosen remains constant, the result would be the desired amount of over- or under-exposure. Correct?

that's right. I check all my lenses manual or automatic, for exposure when I get them, helps "learn" their performance. once you know they have a slight error, dialing in the EV is a good solution, and on the *istD it works in manual also so you don't even think about it. push the green button and you have it perfect.

Glad you said that about using TCs. I remember using the 1.4 TC on my 50-135, and having to use EV comp to get the right exposure.

this is an important point on the K10/K20.

I can almost see EV comp being more useful in M mode, than in Av or Tv- after all, as far as the latter two modes are concerned (and as I just learned last night), all the camera is going to do with your EV setting is adjust the opposite value accordingly. At least in M you would still have complete control over your shutter and aperture settings. Or am I still missing something?

Interesting point about using older manual lenses, good to know.

nope you pretty well have it here. I just wish the K10D had it in manual, because it would make exposure for my 300F4 and 1.7x AF TC much better

The real problem is the fast l apature lenses on the K10. faster than F4 these lenses under expose, slower than F5.6 they over expose.

*pasipasi* · 01-12-2009, 02:09 PM

I've had the k20d for some time now and I didn't know this. Very useful info and maybe I'll be using the manual lenses on the dslr a bit more from now on.

AndrewG NY · 01-14-2009, 07:10 AM

This actually bit me this past weekend, my first weekend out with K20D. Caused some surprise and confusion when I was using the green button for stop-down metering with some Pentax-M glass--I had left comp on from a previously-mounted autofocus lens and assumed that I would need to dial in some comp manually after green button but found that green button exposure was much further off than I had expected. Anyway, I think its a *very good thing* to allow it.

AndrewG NY · 01-14-2009, 07:17 AM

Originally Posted by alohadave

That would have given you a 4 stop over exposure (assuming ISO 200 as your base, 5 stops with ISO 100 as your base).

I think what he means is that in manual mode, with the +2EV dialed in he had to add two stops worth of ISO (200->800) to zero the meter. So it would have overexposed by the 2 stops he unintentionally was asking for.

I sort of wish that some of the viewfinder warnings like EV-comp-applied, for example were orange, instead of green...or maybe they should blink.

denisv · 01-14-2009, 08:44 AM

I think EV compensation in M mode is for controlling flash power...