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02-14-2008, 02:28 PM   #16
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So Nikon has M + Auto ISO? I assume that Nikon lets you set the camera so that it will NOT change the shutter speed, right? Then it sounds as if the "TAv" spot on the dial may be unique to Pentax, but the practical capability is not.

In response to those who think the Nikon system is better, I'm inclined (based on your own descriptions) to disagree. TAv lets me control two of the three settings, and lets the camera adjust the third. I don't tell the camera how to do its job, and it doesn't tell me how to do mine. (Well, I do get to limit the ISO range, but other than that....)

I think of TAv as "almost full manual." If it's a one-variable mode, then I only want to think about one variable being in play. I don't want it to adjust the third, and maybe also adjust one of the others. That's not TAv, that's "TAv but more Av than Tv" and, well, that's not going to fit on the dial. If I am in TAv mode shooting sports at 1/300th sec and, say, f/2.8, I don't want the shutter speed to change. That's the point. Otherwise, I'd shoot in Av mode using Auto ISO. I know it's not QUITE the same thing as Nikon's M + Auto ISO, but it sounds similar.

TAv mode of course doesn't mean you can stop paying attention to the exposure meter! While many people who are afraid of M seem to be willing to work with Tv or Av, I have a strong suspicion that TAv is most appreciated by those who would use M instead, if TAv weren't available. I shoot almost entirely in M or TAv on my K10D. On my *ist DS, I shoot almost entirely in M.

Finally, it's very nice to know that in M mode, I'm going to be blamed for everything, but if I'm willing to let the camera deal with the ISO only, I can switch to TAv with a click of the mode dial. It sounds like, on a Nikon, I'd have to go into the fn menu and switch from M + fixed ISO to M + Auto ISO. Maybe it's easier than that. But I can't imagine it's easier than turning my K10D's dial one notch.

Will

02-14-2008, 02:56 PM   #17
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I'm fully with twinda1.
TAv is identical with M + Auto-ISO on a Nikon. It's just another name.

But Nikon has a feature that Pentax has not.
Nikon has Av+Tv-max+Auto-ISO.
You can set A and a maximum T.
You can define a shutter time T at which Auto-ISO jumps.
Very useful for action.
twinda1 already explained it above.
02-14-2008, 04:52 PM   #18
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I don't feel TAv is identical to M + Auto-ISO because of how the Auto-ISO works differently. The Nikon system has it's disadvantage of not adapting itself to different focal lengths (to my current understanding, please correct if I am wrong). It won't care if you're using a 12mm ultra wide or a 300mm telephoto. If you have 1/125set for as a threshold, that's what it'll hold you to.

My primary use for TAv is for controlling consistent exposure within the same scene. I would not be using TAv to shoot a scene where there are great variance in amount of light. So yes, the Nikon's idea will work identical here.

The Nikon will have the bonus of being able to take pictures of scenes outside of your desired Shutter speed range to maintain EV without additional adjustments, but I would never be in TAv mode under those situations because I would be in a different mode to begin with.

In twinda1's example, I would be using Hyper Program with my Program Line set to Speed with Auto ISO enabled. Which I feel would give me more flexibility than Nikon's M + Auto ISO. In this mode, it would already default to using large apertures. If I realize the dof is too narrow, I adjust my aperture (front dial for me). If I realize I want faster shutter speeds I adjust my shutter (rear dial for me). Need a reset back to full auto? Green button.

Now if it was Auto focusing in twinda's example... I'd take just about any recent Nikons over my Pentax K10D
02-14-2008, 09:23 PM   #19
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On the Nikons, M+Auto-ISO is exactly TAv, except that you can't (at least on the D70) set the lower bound of the ISO range. Not a big deal, since when was the last time you set the lower bound to anything other than ISO 100? Hyper-Program+speed line on the Pentax is a good idea, but still doesn't let me suggest a minimum shutter speed, and it's still optimizing the shutter speed for camera shake as oppose to subject motion blur. As for the Pentax making use of the focal length to derive a shutter speed when adjusting ISO automatically, on the Nikon you just directly set the slowest shutter speed you want, which is much better as it lets you choose something like 1/125 to stop motion when shooting say a 31mm lens @f/2.8 with existing light.

I'm also not suggesting that Pentax reduce the functionality they have, just augment it. TAv working like I describe with an optional threshold would really rock. It really would just be another option in the menus that says something like "TAv shutter speed is threshold".

I'm actually kind of surprised that this is controversial. If you're using TAv and you're not getting the occasional over-exposed image, I submit that you don't need to be using TAv, because you have time to notice the ISO warning and manually adjust the shutter speed appropriately.

02-15-2008, 02:49 PM   #20
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auto-compensation?

i agree the requested feature would be cool and not so hard to implement, though it is arguably quite a rarely used one.

however, about the overexposure issue, would that auto-compensation feature work in tav? i wonder if it does work, which setting it would chose to affect, boost the shutter or close the aperture? maybe it is worth a try, twindal?

about the nikons: i think it must be obvious that the feature on them which was discussed is overall more limited than tav (no exposure compensation, iirc, for one), it does have the noted advantage, but it is only an advantage in this very particular case. correct? so , although this sounds like a desireable feature and something which could be easy to add to a small fw upgrade, being realistic, overall i still prefer the k10d, by far.

just my two cents
02-15-2008, 03:54 PM   #21
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QuoteOriginally posted by twinda1 Quote
On the Nikons, M+Auto-ISO is exactly TAv, except that you can't (at least on the D70) set the lower bound of the ISO range. Not a big deal, since when was the last time you set the lower bound to anything other than ISO 100? Hyper-Program+speed line on the Pentax is a good idea, but still doesn't let me suggest a minimum shutter speed, and it's still optimizing the shutter speed for camera shake as oppose to subject motion blur. As for the Pentax making use of the focal length to derive a shutter speed when adjusting ISO automatically, on the Nikon you just directly set the slowest shutter speed you want, which is much better as it lets you choose something like 1/125 to stop motion when shooting say a 31mm lens @f/2.8 with existing light.

I'm also not suggesting that Pentax reduce the functionality they have, just augment it. TAv working like I describe with an optional threshold would really rock. It really would just be another option in the menus that says something like "TAv shutter speed is threshold".

I'm actually kind of surprised that this is controversial. If you're using TAv and you're not getting the occasional over-exposed image, I submit that you don't need to be using TAv, because you have time to notice the ISO warning and manually adjust the shutter speed appropriately.
I am curious,

How do you switch auto ISO on/off on the Nikons?

Can you recover a real M mode instantly or do you have to enable/disable auto ISO in some menu?

Also do they have the equivalent of the green button in TAv?
02-15-2008, 09:18 PM   #22
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QuoteOriginally posted by lol101 Quote
I am curious,

How do you switch auto ISO on/off on the Nikons?

Can you recover a real M mode instantly or do you have to enable/disable auto ISO in some menu?

Also do they have the equivalent of the green button in TAv?
The auto ISO on/off is controlled via a setting buried in the shooting menu, and it's the only way to access the function, so you can't recover M mode instantly. This is a sore point among some Nikon users who (rightfully) believe M mode shouldn't have any automation around exposure control at all. And no, Nikon doesn't have the well-conceived Pentax green button. Mind you, this is all with the Nikon D70.
02-16-2008, 02:23 AM   #23
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QuoteOriginally posted by twinda1 Quote
The auto ISO on/off is controlled via a setting buried in the shooting menu, and it's the only way to access the function, so you can't recover M mode instantly. This is a sore point among some Nikon users who (rightfully) believe M mode shouldn't have any automation around exposure control at all. And no, Nikon doesn't have the well-conceived Pentax green button. Mind you, this is all with the Nikon D70.
OK that's what I seemed to remember from manipulating a D300 too.

So the answer is simple: there is no equivalent of TAv mode in other brands.

I often use TAv mode instead of M when I use flash and want to have an equilibrated background light, but also in varying lights when using longer focal to ensure DoF and sufficient shutter speed.

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