T3i metering with preset long telephoto

[lin]

I have a Canon T31 and a very good preset 500mm preset lens. In "live view" (mirror up) it exposes correctly. In normal (mirror down) overexposes by 1 or 2 stops. Metering mode is set to "evaluative" and everything else is equal. [Tripod and wired remote shutter release].

Any ideas?

[ebiggs1]

B from B,

"When you're in viewfinder mode, the metering system thinks it's looking through the lens at full aperture (f/8), so it adds a stop of exposure to account for the fact that the picture will be taken at f/11. But in live view mode, the camera knows it's already seeing the scene at f/11, so it doesn't add an unnecessary stop to the exposure."

This can not happen. That is why it is wrong.  If the lens is set to f8 the exposure will be measured for f8 and the T3i will complete it at f8.  If you wanted to shot at f11, you must manually move the setting on the lens to f11.  The T3i will then make the proper exposure measurement and take the shot.  I don't use live view so I didn't comment on it.  But it will not change either in my guess.  It can't.  The T3i meters whatever the lens is set on.

Manual mode and a fixed ISO will work (view finder).  I have done it thousands of times.  It is exactly how I use my old FD lenses.

[Ray-uk]

Bob, can you please choose a larger font ?

I know I'm getting old but I can't be the only one who struggles to read your posts

Thanks

Ray

[Waddizzle]

Are you using LiveView to magnify.  In my experince, the location of the focus box in LiveView seems to affect the metering.  I suppose how much affect will depend upon the scene.

If you center the focus box, without any magnification, then you should get metering that is very close to the viewfinder exposure.  Once you begin moving the zoom/focus box away from the center area in LiveView, the camera will begin to meter differently.

[ebiggs1]

lin,

The 'auto ISO' is messing you up.  It matters not to the camera what aperture you set if you are in manual. Nothing changes. People that suggested so are wrong.  The variable is auto ISO. Set it to a fixed number and try again.

I shoot pre-set manual lens a lot with various cameras and it works very well.

I have the very lens you have but under a different brand name.  They were branded by several companies and are still available.

[kvbarkley]

Then why does it work in live view? That still has auto-iso.

[ebiggs1]

I don't know because I don't use live view.  But it will work just fine using the view finder.  The auto ISO is the only variable if all is set to manual.  I see no good reason to use auto ISO in manual mode.  Is it manual mode or not?

[Stephen · Accepted solution]

I'd like to weigh in, if I may? 

Seeing as the lens is a Vivitar T-mount lens, the Rebel T3i has no idea what lens is connected to it (or that a lens is even connected). Even if you were to use an EF-adapter, my guess is that there are no electronics in this lens to communicate with the camera. In most cases, the camera will read "F00", like Wadizzle said above. That means either no lens is attached, or the camera doesn't recognize the lens.

We obviously haven't tested these lenses, so we can't guarantee anything, but we've found that they work best in fully manual mode, so  you can tell the camera what you're doing. Remember, the camera doesn't even know a lens is attached when you're looking through the viewfinder. 

On the flip side, when you use Live View, the camera's electronics doesn't know about the lens, however, it can tell optically that *something* is there. That means that it will expose the shot to the best of its ability.

That's why the "automatic" settings will be all over the map, and remember, we guarantee nothing when you're using a non-Canon, non-EF/EF-S lens. 

I hope that helps!

[lin]

Thank you, very much. 

Notwithstanding me earlier avoidance, I had finally arrived at the Manual solution.  Not only is that what the camera prefers (and responds flawlessly to), but at least for them of us who cut our teeth on non metering 35mm cameras (an Argus C3 & a Pentax H2a, in my case), the old rules of thumb like "sunlght 16" come back.

AND, these Canon SLRs are considerate enough to provide a great, easy to refer to metering system to confirm our manual efforts.

That lucid and concise explanation of what causes the different results was spot-on, so for all of the others wrestling with this, Problem Solved.