TAv mode vs. M mode with auto ISO...

Discussion in 'Pentax' started by shaloot!, Mar 6, 2009.

  1. What is the difference between the two? Why is there a mode that is basically (my understanding) Manual mode with auto ISO? When I can just choose auto ISO in regular M mode?
    Any frequent users of the TAv mode? I don't think I've actively chosen that mode to take a photo... ever. That and the Sv mode. So why is there a TAv mode and how do you explain it (and the benefits)?
    Thanks guys.
     
  2. The TAv mode essentially allows you to set the shutter speed, and the aperture while the camera adjusts for the exposure using the ISO. Let's say that you are shooting some kids playing.. so you need the shutter speed to be at 1/250, and you also would like a shallow depth of field so as not to get background clutter.. so you set your aperture at f4. At this point these are constants with the Tav mode.. and as the light changes the camera compensates with the ISO to get the proper exposure.
    The Sv mode just sets your shutter speed to be a constant, and your ISO is set by you, the camera adjusts the aperture to get the proper exposure.
     
  3. Nice summary Haig. I rarely use TAv or Sv, preferring Av and M in that order with ISO 400 as the baseline. But my shooting partners go gaga over the TAv capability on my Pentax. It's the greatest invention since autofocus to them. I think that if I hadn't imprinted on film so long ago, I would view ISO as a main variable that they do.
    ME
     
  4. trw

    trw

    Well, one major benefit is having a separate dial setting for TAv so you don't have auto-iso turned on in Manual mode when you think you're in full-manual mode.
     
  5. Haig... you have described Sv mode incorrectly. You set your ISO and the camera adjusts the shutter and aperture accordingly.
     
  6. You are right Patrick.. I meant to say Tv mode..
     
  7. After reading this I think I will have to give this setting a go as I can see its uses now where as previously I just skipped over this setting.
     
  8. I use TAV mode allot, but do not use the auto ISO. I just don't trust it. I like having the aperture, shutter and EV controls in my hands.
     
  9. Javier, isn't TAv mode with auto iso then? I'm not sure what you mean when you say use TAv mode, but don't use the auto ISO...
     
  10. Somanna, Yes, I set the high and low ISO to the same setting. Really I could do the same in Manual but being in TAV mode is cool since tha canikon folks I run into don't have that setting. :)
     
  11. Firstly, there is no auto ISO in manual mode. If there was, it would cease to be manual and would become an autoexposure mode (which in a sense it still becomes when using P-TTL flash). A key difference is in the way the meter behaves--when you're in an AE mode, the settings are automatically pegged to 'neutral', exposure only adjusted via exposure comp. In manual mode, this is not the case--the meter just tells you the way it is and it's up to you to decide where to place exposure.
    Javier, that use of TAv with no ISO range doesn't make any sense...everything is fixed, and you don't even have the meter helping you like it would in M. Do you just use green button a lot? I believe there's a custom setting "Auto EV Compensation" on K10D and K20D that tells the camera to automatically adjust exposure when it reaches limits--instead of the numbers blinking and allowing you to take a picture under- or over-exposed...don't know if you have this enabled or if its affecting you. What is exposure comp changing if everything is set to be constant, anyway?
    I don't get 'not trusting auto ISO' What is there not to trust any more than auto-anything-else? It uses the same metering logic for input, and you can see it in the viewfinder just like shutter speed and aperture. It sounds to me if you really want to fix ISO you should be using Sv instead. I guess the Canikon folks take a lot more interest in your camera settings than they do mine, but in particular Canon seems to only grudgingly include Auto ISO features in their camera--until recently they only allowed in in their full auto/scene modes if I remember correctly, and only in full stops.
    I think the TAv mode can work pretty well as long as you set within reason and are not bumping against the ISO limits from shot to shot. One way of looking at TAv mode is that you're taking direct control of the two exposure attributes that are perhaps most relevant from a sense of creativity--shutter & aperture, and allowing the camera to automate the remaining factor--sensitivity.
     
  12. Andrew,
    Both the K10 and K20D have a tendency to always pick the lowest ISO setting regardless of conditions outside. To answer your question, yes, when in green mode, I use the ''GREEN'' button allot. Even at that, the green button will tend to leave me underexposed. When having to deal with what I have to deal with allot, in shooting from crazy sunlight into dark shadows, you learn to deal with things a different way. While my use of the TAV mode may be wrong and A lousy technique, I am happy with my results. As far as my comments on the canikon folks, that was a ''joke'' , (hence the smiley) ; because it is one thing Pentax has that to my knowledge no others do, yet Pentax does not even market it like many other things...So for me, I like having the Aperture and shutter speeds at ''my'' control, not the cameras..Maybe I have been shooting to much film and have developed a bad habit, bad technique.
     
  13. Javier, taking control is cool--I get that. What confuses me about what you're describing is how you end up obtaining proper exposure if all the variables are fixed. I think there's just something I'm not getting about the way you're using it. Perhaps if I tried to do the same thing I'd see something about the behavior that allows it to work. Are you familiar with the somewhat obscure (by this I mean infrequently mentioned on this forum) "Auto EV Compensation" custom setting? How is it set on your cameras?
     
  14. Andrew, I live off the EV compensation settings and fully take advantage of that. But to answer your question, the way I get proper exposer is to raise or lower the shutter speeds or change the aperture. This is why the two wheels are important to me. To change those things has become second nature. So essentially I am using it like a mechanical camera. I find this way especially useful when shooting in dark conditions.
     

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