Error message

[fishguybob58]

I use a Canon T7 with the kit 75-300mm lens. While taking photos, all of a sudden I got an error message which read that there was a communication error between my camera and lens. When I got home, I cleaned all the contacts, reset the camera and took the battery out for 3 minutes. After doing this, I turned the camera on and was able to take several photos indoors with no problem. When I went outside, the first photo I attempted to take, I got the same error message. turned the camera off, indoors works fine, outdoors, error message. I then tried shade to sunlight. If I'm in the shade taking a photos of something in the shade, no problem. If I'm in the sunlight or taking a photo into a sunlit area, I get the error message. I tried the lens on my wife's T6 and the same thing happens. All other lenses work fine but, I really need the 300mm for my photos. Any ideas?

[jrhoffman75]

Welcome to the forum.

Based on the troubleshooting you did it seems the 75-300 is faulty.

You need to investigate costs for repair vs replacement.

A very good lens is the Canon EF 70-300.

[fishguybob58]

Thank you. It was just throwing me off that would only not work in sunlight. I couldn't find anything that indicated that there a light sensor in the lens. I know that there is in the camera.

[kvbarkley]

There is no light sensor in the lens itself, but a light leak in the mount could affect the camera. The 75-300 is not one of Canon's finer efforts. It is every inch a budget lens, and tolerance issues in the mount might be indicative of that.

[fishguybob58]

I forgot to mention the problem is with my Canon EF 75-300 lens

[kvbarkley]

Sounds like a bit of gaposis in the 75-300 lens mount. Try wrapping it with gaffer's tape.

[Lotus7]

"If I'm in the shade taking a photos of something in the shade, no problem. If I'm in the sunlight or taking a photo into a sunlit area, I get the error message. I tried the lens on my wife's T6 and the same thing happens."

Sounds like the the aperture control mechanism in your EF 75-300 is not functioning.  If you have the camera set to full AUTO or Program exposure control, indoors or in the shade the lens will likely be set to wide open F/4 to F/5.6 depending on the focal length selected.  Outdoors in bright sunlighnt, the camera is likely asking for a smaller aperture (higher F-number), but the lens is not responding.  Hence the error message.

Normally, Canon EF lenses default to wide open when not on a camera.

To test if this is the problem set your camera to a high ISO.  Then set it to Aperture Priority mode (Av in the creative control section of the Mode Dial). Press and hold DOF preview button. Then rotate the control dial to see if the lens aperture changes.

Alternately, set the Mode to "Av" and set the control dial to f/4.0.  Turn the ISO down to 100. Then try shooting outdoors in sunlight.  If you now don't have an error message a lens aperture control malfunction is confirmed. 

Sometimes a sticky aperture control mechanismcan can be coaxed into operation by trying the following:

*  Mount the lens on a camera with a fully charged battery.

*  Set Mode to Av and set aperture to f/16

*  Press and HOLD the DOF Preview button

*  Gently tap the side of the lens.

*  While still holding the DOF preview Button, press the lens release and remove the lens.

The off-camera lens should now appear to be stopped down if you look through it. 

Turn the camera OFF and replace the lens.  Doing so should return the lens to wide open (f/4).

Running through that cycle a few times may temporarily return a sticky-aperture lens to normal operation for a while, but sooner or later it will stick again, especially if it's stored in a cold environment.

[jrhoffman75]

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@Lotus7 wrote:

"If I'm in the shade taking a photos of something in the shade, no problem. If I'm in the sunlight or taking a photo into a sunlit area, I get the error message. I tried the lens on my wife's T6 and the same thing happens."

Sounds like the the aperture control mechanism in your EF 75-300 is not functioning.  If you have the camera set to full AUTO or Program exposure control, indoors or in the shade the lens will likely be set to wide open F/4 to F/5.6 depending on the focal length selected.  Outdoors in bright sunlighnt, the camera is likely asking for a smaller aperture (higher F-number), but the lens is not responding.  Hence the error message.

Normally, Canon EF lenses default to wide open when not on a camera.

To test if this is the problem set your camera to a high ISO.  Then set it to Aperture Priority mode (Av in the creative control section of the Mode Dial). Press and hold DOF preview button. Then rotate the control dial to see if the lens aperture changes.

Alternately, set the Mode to "Av" and set the control dial to f/4.0.  Turn the ISO down to 100. Then try shooting outdoors in sunlight.  If you now don't have an error message a lens aperture control malfunction is confirmed. 

Sometimes a sticky aperture control mechanismcan can be coaxed into operation by trying the following:

*  Mount the lens on a camera with a fully charged battery.

*  Set Mode to Av and set aperture to f/16

*  Press and HOLD the DOF Preview button

*  Gently tap the side of the lens.

*  While still holding the DOF preview Button, press the lens release and remove the lens.

The off-camera lens should now appear to be stopped down if you look through it. 

Turn the camera OFF and replace the lens.  Doing so should return the lens to wide open (f/4).

Running through that cycle a few times may temporarily return a sticky-aperture lens to normal operation for a while, but sooner or later it will stick again, especially if it's stored in a cold environment.

---

Since OP states there is a communication error I suspect your overall assessment is correct - diaphragm not closing - but since there is no signal getting to the lens I don't believe the trouble shooting will work. 

[Lotus7]

Remote diagnosis, with incomplete data, is always a gussing game, but from the reported conditions it appears that possibly  the feedback from the lens is not correct.  There is no way to easily determine if (a) the camera command to the lens to change aperture is not being received (as you mention) OR that (b) the lens is not responding and not sending back the aperture set response which will happen with a slugish or sticking diaphragm.  Either condition could create the OP's indicated conditions, which is why I suggested trying to manually check if the diaphragm moves by trying to force a small aperture setting.

ultimately, it really doesn't make a difference, but the "long-shot" of trying to cycle the diaphragm can't hurt.

The main point of my response was that the error may be caused by a non-responding aperture which explains the difference between indoor (low-light, wide open diaphragm) no error message, and outdoor (higher-light, stopped-down) operation causing an error message, rather than some kind of obscure light leak affecting the auto exposure detection.

FYI:  The eight contacts on Canon EF/EFS lenses, and the 11 contacts on Canon DSLR cameras individually carry power and data.  Communication between the camera and the lens is fully bi-directional and uses an 8-bit serial protocol.  The separate pins carry Motor power, Logic power, DCL (data to lens), DLC (data from lens), camera clock, and several separate signal and motor ground returns. 

The DLC stream lets the camera processor know if, and when the lens has achieved the correct aperture so that shutter release can then occur. Incorrect feedback will cause a "Lens Error" message to be generated.

[ebiggs1]

" I tried the lens on my wife's T6 and the same thing happens."

This kinda says it all. The lens needs service or replacement. It is unlikely to fix itself albeit perhaps temporarily.