7D + 400/5.6 in Tv mode uses 6.3!

[JDMvW]

<p>If you want f/5.6 then put the camera on manual and set it there. I think it most likely that the other perturbations that bother you are "features" not "bugs."</p>

[omar]

<p>Hi<br>

I have the "same" problem with my Canon MarkIV + Canon 400mm 5.6.<br>

Best regards</p>

<p>Omar Brännström</p>

[steve_wagner1]

<p>If someone is using ISO it's because of the need for split-second decision making without having to worry about achieving a proper exposure or worrying about changing ISO, or at least it should be. Going to manual mode is the opposite of this. Use AV, keep your Auto ISO if you want, or don't, and open up to 5.6. You will stay at 5.6. If the shutter starts to drop below your focal length and you aren't on a tripod, then you can go to auto ISO.</p>

[tele_tele]

<p>Omar:<br />Does it work better if you change Custom Function 1-1 from 1/3 to 1/2 stop?<br>

Full name of the Custom Function is C.Fn I Exposure - Exposure level increments in case the numbering is different on MarkIV.<br>

For me this constant changing from 5.6 to 6.3 (on the same subject and same low light) disappeared when I set this and now it keeps to the lowest aperture of 5.6.</p>

[dcstep]

<p>"AutoISO saves lives in light challenging conditions. :-)"</p>

<p>Well, then don't complain about the results. If you leave two variable open the camera's programs will often change two variables.</p>

<p>Lots of us look in the viewfinder and change either aperture, ISO or S/S with the wheel on the top right, very quickly to suit the subject. You don't have to be in TV to control the shutter speed. Only a slight awareness of the interaction between S/S, aperture, ISO and EV allows you to work in other modes. If you prefer TV, that fine, but turn off the auto ISO if you want only the aperture to change. Go to AV with fixed ISO if you want only S/S to change. You can always see the resultant variable in the viewfinder.</p>

[andrewg_ny]

<p>Not sure about Canon but I think you have a choice between ISO in 1 EV or 1/3 EV steps. If the steps are 1EV, then auto ISO can only move in 1EV increments, e.g. 100-200-400. You've locked the shutter at one particular speed. If the camera's meter says it wants 1/3 EV less light, it's going to stop the lens down 1/3 EV to f/5.6. Possibly this wouldn't have happened if ISO was set to EV 1/3 steps...but you're leaving it up to the camera to decide. As long as exposure is correct, who cares? If you do, you shouldn't use Tv for this.</p>

[test11664875106]

<p>perhaps the camera chooses smaller apperture because engineers are aware that lens performs better when stopped down? since you let the camera control two variables (iso and apperture), you shouldn't expect it to use the same strategy as you would choose.</p>

[omar]

<p>Hi<br>

I use the 400mm 5.6 handheld with Canon MarkIV.<br>

I also use tv offen 1600-2000/s for action and in low light I might go down to 1/640s. I want maximum shutterspeed and low ISO, and not higher aperture.<br>

I use safety shift (ISO) cfn I-8:2.<br>

Regardeless of light i got the shuttertime I think I need, and ISO changes accordingly, but I do not want it to change the aperture.<br>

I wonder if other lenses behaves like this, with my former 500mm f/4 IS I used av so I did not have the same settings. I have ordered the new 500mm f/4 IS II and will test when I got it, but I probably have to wait a year for it.<br>

For instance<br>

Shooting sparrow hawk in air, in this case I used 1/2000s and ISO changes<br>

<a href="http://www.pbase.com/omar_brannstrom/image/128031633/original">http://www.pbase.com/omar_brannstrom/image/128031633/original</a><br>

In this settings I had 1/2500s and suddenly I sparrowhawk was flying/hunting low with background in AV I might got 1/500s? and that would probably be soft compared to 1/2500s and higher ISO with safetyshift.<br>

<a href="http://www.pbase.com/omar_brannstrom/image/128102009/original">http://www.pbase.com/omar_brannstrom/image/128102009/original</a><br>

It will be sharp but the problem is that ISO can get to high and it will be even higher if the camera will set higher aperture than 5.6, like 6.3 or something.<br>

If I set the camera on 1/3 step it sometimes changes the aperture to 6.3 and if I set the camera on 1/2 step it will sometime set the aperture at 6.7 instead.<br>

When I shoot handheld very early in the morning, I might go down to 1/640s so the ISO will not be to high.<br>

Here is a wild red deer running and at 1/640s handheld camera, aperture 5.6 and if it would be at 6.3 och 6.7 the iso would be even higher, there are already to much noise in the picture.<br>

<a href="http://www.pbase.com/omar_brannstrom/image/128322679/original">http://www.pbase.com/omar_brannstrom/image/128322679/original</a><br>

Here is another one with Canon MarkIII instead at 1/640s<br>

<a href="http://www.pbase.com/omar_brannstrom/image/117633427/original">http://www.pbase.com/omar_brannstrom/image/117633427/original</a><br>

Best regards from Sweden<br>

Omar Brännström</p>

<p> </p>

[nathan_b]

<p>Excuse me if I missed the point, but you KNOW you want a specific shutter speed and you KNOW you want a specific aperture. Just put it on Manual and let the ISO float. The 7D will do auto ISO in M mode.<br>

I chose Canon for a variety of reasons, but I do understand that Nikon is just ever so slightly smarter when it comes to automatic exposure settings. I suppose you just can't have the best of both worlds.</p>

[omar]

<p>Hi<br>

On my MarkIV I can not exposure compensate at all if I put it on manual. I offen use like + 1-2 for birds against clouds and sometimes when it is dark outside I use -2.0 exposure compensation like this wild red deer<br>

<a href="http://www.pbase.com/omar_brannstrom/image/128581441/original">http://www.pbase.com/omar_brannstrom/image/128581441/original</a><br>

Is it possible to exposure compensate with 7D in manual and auto ISO?<br>

Best regards from Sweden<br>

Omar Brännström</p>

<p> </p>