Occasional Horizontal Lines on Images

I have a Rebel XT. For the past month or more I've been seeing narrow bands of horizontal lines on some of my images (see big cropped image below taken at ISO 800). It happens so infrequently that I haven't been able to identify the cause although I have a couple of suspects.

1. High ISO? I generally shoot at ISO 400 or less but occasionally have to resort to 800. I haven't noted that the lines are consistent with ISO 800, and dark shooting conditions, but it's possible

2. Bad / unstable Compact Flash card? - I have about 6 cards that I rotate through before I re-format the first and start over.

3. Camera Sensor? - I'm hoping that it's not this. I've taken a little over 20.5K shots with this camera.

If anyone has any ideas or has experienced a similar issue please let me know.

Thanks

Sticky shutter curtain???
The curtains travel vertically and it they stutter on the way down, there could be uneven exposure in horizontal bands.

This is a total guess, by the way.

Thanks for your input Xarqi. I'm not sure if I'll discusover the cause but if it remains an isolated issue perhaps I can put up with it.

I would have it repaied...why chance ruining good pictures?

xarqi wrote in post #3945669
Sticky shutter curtain???
The curtains travel vertically and it they stutter on the way down, there could be uneven exposure in horizontal bands.

This is a total guess, by the way.

Sticky shutters usually show very discernable arcs of light (not banding like as seen here). I'd say more testing is in order to determine the cause. I'd look to eliminate the CF cards and/or the card reader (if you use one), and, of course, the first step is to find the shooting conditions under which the issue can be reliably replicated. Even if it's not something simple that you can fix yourself with a new card or card reader, it will greatly help Canon in determining the problem and speed the return of your camera.

Mark

That looks like classic banding.
What is the history of that shot? How was it processed?

Reason I ask is banding commonly occurrs with high ISO photos that are underexposed. When opened in software that has auto settings , the software brightens the image , resulting in obvious banding , just like your example.

Dave hit right on the nose, that is the classic sign of banding caused by high ISO. I sent both of my MKIIn in at the end basketball season for this reason. If your camera is still under warranty Canon will fix for free. If you do send it in make a cd with images of the banding and ship with camera, service center does look at these.
Good Luck
Romeo

Yep, underexposing @ high ISO Stephen. It happens more with some lenses than others, but is quite common.

Thank you Super, Mark, Dave, Gromeo and Wayne. I'm quite sure that I was underexposing in this instance.

Dave I converted to Jpeg using the Zoombrowser. I know that everyone will ask why I'm not using Digital Photo Professional, or something else, but I've been on a Windows 98 SE machine for quite a while and DPP wouldn't work. I've also got an XP machine where I can run DPP.

I'll do some more investigating before I send the camera to Canon.

Thanks again!

That's not the high ISO banding I am used to. I remember seeing a picture that had banding almost just like that, but for the life of me I can't remember what the problem was. It might have had something to do with AI servo focusing mode.

Here is a thread where the picture the OP posts looks like it has a similar problem.

https://photography-on-the.net …3&highlight=foc​us+banding

Someone suggested on that thread that electromagnetic interference from a cell phone could possibly cause it. Someone else suggested that the lens was focusing during the capture and that caused the banding. Here is another thread with some pics that look very similar to yours.

https://photography-on-the.net …2&highlight=foc​us+banding

Thanks Jason. I'm beginning to think that it's a high ISO + underexposure issue.

that's a lot of noise for iso800...
shoot 1600 overexposed by a third or more stop then see if the banding is still there..