EOS 80D Overexposure on 80D problem

[BlairW]

I have a Canon 60D and an 80D, using a couple of my lenses or a Tamron 2x TC on the 80D (I know you guys are not a fan of converters) but I wanted to see if I could reproduce the same problem. That shooting in sunlight the camera is three f-stops too bright. If I manually correct it the exposure is just right. I noticed too even thou I set the ISO at an upper limit of 400 it is shooting at 6400 in green mode or program mode. I’ve cleaned the contacts with a contact cleaning kit. I don’t know if the camera has a metering problem or if I’ve changed one of the settings. BTW I'm not shooting into the sun or have the sun at my back, it's overhead. thanks, Blair

[Waddizzle]

Setting a limit on ISO has no effect on Green [A] Mode.  Ditto for Program Mode.

If you want to test the camera body, eliminate the number of possibilities.  Stop using the extender, or tell what lens you are using.  

If the camera is not exposing properly without the extender, check your exposure compensation settings.  Also, make sure the camera is not in a multiple exposure mode.  Your 80D has features not found in a 60D.

[BlairW]

I'm using the exposure compensation to adjust for the over exposure – f/3 stops. I as a rule don't use the TC I just wanted to see that would happen on a lens working properly. For the most part the problem with overexposure is hit and miss except for one lens I bought more of a novility, a Kenko 400mm Mirror lens. Every time I place that lens on my 80D the camera over exposes the shot. I works fine on my 60D, it’s not that I care all that much about my 80D working with a mirror lens I'm hoping its not an indication of that my 80D is showing early signs of a problem that's going to worsen over time.

[Waddizzle · Accepted solution]

That is a fully manual lens with a preset aperture.  Any shooting mode that tries to adjust the aperture will give unexpected results.  

You should only set the camera to either M or Av modes when using it.  Turn off exposure compensation until you can get your exposures properly set without it.  I would also set the ISO to a fixed value until you get Shutter Speed figured out.

[BlairW]

thank you very much for the information and replies...I'll try as you have suggested 

[ScottyP]

That mirror lens is an f/8 lens and your teleconverter robs a stop, so it is a max aperture of f/11.  I'm kind of surprised it can even autofocus with the TC on it. 

[Waddizzle]

---

@ScottyP wrote:

That mirror lens is an f/8 lens and your teleconverter robs a stop, so it is a max aperture of f/11.  I'm kind of surprised it can even autofocus with the TC on it. 

---

That's just it, it doesn't autofocus at all.  It's fully manual.  It's likely that the extender could be confused when used with a lens that cannot communicate with it.  It could be reporting erroneous aperture info to the camera body.

[BlairW]

I don’t typically use the TC, I just wanted to see what would happen with other Tamron and Canon lenses that work as they should regarding exposure without the 2x TC added. I expect the mirror lens to behave the way it does since I can’t control the armature & should be shooting in manual. However, I don’t understand why when I add the TC to a zoom or prime lens it shoots three f stops over exposed. As far as the extender is concerned I could do without it. For times when I want a long focal length (shooting wildlife) I use my Tamron 150~600mm G1 lens. Like I posted above my only concern is that this is an early indication of something going wrong with my camera body. I only bought the mirror lens because I’ve never had one. You get what you pay for and really the IQ is better than what I expected for a couple hundred lens. I place the same combo of the Tamron extender and any of my lenses on my 60D and the exposure is as it should be.

[Waddizzle]

Many cameras cannot AF with apertures smaller than f/5.6.  Your 80D has several AF points that can focus out to f/8.  The AF point to use is always the center AF point.  

When you add the extender to your. 150-600, the minimum aperture easily exceeds f/5.6.  In fact, with an aperture range of f/5-6.3, the lenses are already exceeding the f/5.6 limit.  These limits are impose in firmware because the designers feel the camera may not focus consistently and accurately with narrower apertures.

So, why does the lens seem to AF properly, despite exceeding f/5.6?  It works because the lenses reportedly do not report accurate aperture data during focusing.  In other words, the lenses fool the camera into thinking that it is focusing a lens with a wider aperture.

Using an extender only makes the problem worse.  Your AF system will not work properly with the 2x extender, and the 2x extender will not work with [just] any lens in your bag.  Personally, I wouldn't worry about my camera failing because a third party extender does not work meter well when used with the camera, especially 2x extender.  It is to be expected.

[EDIT]
The extender is designed to work with specific Tamron lenses.

[BlairW]

So, when I send the camera erroneous data (thru my mirror lens or combo of TC +lenses) it thinks it’s making the right exposure?