Sigma 18-250 over exposure

I have the first version of the Sigma 18-250mm zoom lens. I have used it on my Canon 7D and the Rebel T3. When using the AV setting, my photos are overexposed. I get a lower exposure setting when using AV. The other settings work fine. I do not know what is wrong. Looking for ideas in resolving this problem.

Thank you.

Check the diaphragm is working by dialing in a high f-number in Av mode, peer down the objective end of the lens, and press the DoF preview button.

If that's at least moving, next figure out if the metering (shutter speed vs. aperture) is being thrown off (compare with other lenses at the same settings, on both the camera and the lens). EOS meters with the lens wide open and calculates the other parameters based on the mode, so if the diaphragm is unable to open all the way shots will be overexposed. If the metering looks correct, the diaphragm might not be closing down sufficiently when the shot is being taken.

Different lens designs do lead to slight exposure variations, I've seen around +/- 2/3 of a stop in my collection.

If you determine a fault, use exposure compensation to determine the amount of overexposure before returning or sending in for service.

The DoF seems to be working. Its moving. The metering seams to match TV and AV.

So in Av you get a different exposure than in say Tv or M with the same settings - ISO, SS and aperture? Or are the settings different but should come out to the same exposure?

I think we need more specific information and examples to stand a chance of suggesting what the issue might be.

I read a different exposure on AV showing less light causing the over exposure.

So exposure is determined by how much light is coming into the camera (not lens) with the lens wide open. So that would mean the lens is reporting a more open max aperture to the camera in Av than Tv so the camera in Av thinks the maximum open aperture is larger than it really is and thus the scene is dimmer than it really is. I would have thought if the camera was getting a larger max aperture (smaller f-stop) then you would be able to see this on the camera screen (i.e. you could dial the aperture to f3.2 at 18mm or f5 at 250mm for instance).

I assume this is on a tripod with a static scene? This is how I would test this. Make sure the zoom is not changed, since this is a variable aperture zoom. Meter wide open with Av at max aperture + 1 stop and then with Tv with the same SS as Av gave you. If it gives you a different ISO or aperture then:

with the same setup be in Av and see what the largest aperture (smallest f-stop) you can dial in is. The switch to Tv and change the SS to get the largest aperture you can. Is this the same as the largest Av aperture?

I did not use a tripod but I did my test on a stationary object. This test was done with three cameras ( 7D and 2-Rebel T3). I will test with a tripod tomorrow and report my findings.

What metering mode are you using?

I tried a couple of shots with the tripod using AV and TV with the evaluative m4etering mode, ISO 100. Both exposures in the AV and TV seems to match. I will try some more shots this weekend.

Do you know how to post photos on POTN, using photos with intact EXIF data (not images which area 'print for the web')? It would help to see what your complaints reflect.

Thanks for suggesting the use of the tripod. As ti turns out, I have over exposure on non-automatic modes. The first shot if using the shutter priority ISO 1/80 f/11.

The second was aperture priority with the same exposure. I used both a Rebel T3 and a Rebel T6 with the same over exposure of 3 stops. Firmware is current on the cameras. ON automatic mode, the lens seems to operate correctly.

I am looking for suggestions. Do I need a new lens. Its the old version of Sigma 18-250mm. Is this serviceable?

If you're on shutter priority, dial the shutter speed up. 1/80 is way to long for that sunny day. Try shooting at 1/1000
See if the camera adjusts accordingly for f-stop.

I took a couple of more shots today with a higher shutter speed on a sunny day. I seems ok but when I try to use the smallest aperture, the camera suggest a slower shutter speed causing overexposure.

What's your metering mode set at?
In your example pics, the camera may have been set to spot metering and that's why the house looks okay but everything else is blown out. Evaluative metering would compensate for the whole scene and adjust the exposure accordingly.
Just a guess.

I used evaluative metering on the exposures.