Question: Why does disengaging the Lens blow out the Image on my Canon 5D MIII?

Dear Fellow Photographers,

Recently, I watched Creating Timelapse Video with Richard Harrington on Lynda.com. Today I decided to test out what I had learned by shooting freeway traffic on a bright sunny day in downtown Seattle.

One of Richard Harrington's tips is to disengage (twist the lens slightly) to keep the aperture from changing slightly for every shot taken during a time-lapse. So I tested it out only to find my images overexposed. Is it because I should only disengage the lens for long exposures time-lapses at night? Or is it because I didn't cover the viewfinder? Or ..... I dunno.

Another tip is to enable Mirror Lock-up. I got a bit paranoid from not hearing the shutter click and immediately turned it off. Any feedback or help is greatly appreciated...

Here are my notes so far from the course:

Time-lapse Camera Configurations for Canon 5D Mark III
• Turn off Auto Lighting Optimizer for Manual mode (if shooting in JPEG) & Noise Reduction to eliminate camera post-processing.
• Engage Mirror Lock-Up to reduce Camera Vibration from the movement of the Mirror.
• Set Custom White Balance (Sun, Shade, Cloudy) to prevent camera from changing Color Temperature in the middle of the sequence.
• Set Camera Lens to Manual after framing and focusing the shot.
• Lock Aperture by disengaging Lens from Camera Body with a slight twist of the lens. All settings must be set before this step.

Any suggestions or thoughts...I did DO a timelapse without disengaging the Lens. I haven't run it through post processing yet. The images are exposed just fine.

One last question: Any suggestions on finding a good, cheap ND filter for a 16-35mm lens? I wanted to drag my shutter speed today but was unable too given the bright sunny conditions. I do have a polarized filter, but don't like the effect of having the sky darker in some areas than others...

Sorry for the long winded post...I am a bit excited about this "Creative Endeavor."

Were you holding down the DoF preview button when disengaging? If not, the lens was shooting wide open, not at the aperture that you wanted it at.

Nope! I was not holding down the Depth of Field Button when disengaging. I completely forgot about it. Not sure how I will hold down the DOF button and the Camera Lens disengage button at the same time whilst twisting the lens, but will practice tomorrow.

You are spot on. Thank-you for the feedback. I knew I was missing something.

I'm confused. Why not shoot in manual mode so you can set the aperture and keep it consistent. And if you want it to expose correctly in changing light do it in Av so it adjusts the shutter speed for you. Also, shoot in RAW so you can set the white balance to your liking later. I don't have a 5d3 and have not shot any time lapses so forgive me if my questions are off base.

+1 to what TTuna said.

That just sounds like incredibly stupid advise to me. Just a matter of time before someone posts a sad story on here about how their disengaged lens fell off the walkway and smashed on the road/car below.

Agreed, that doesn't sound like very good advice. I believe it is meant to help with exposure changing from night to day or day to night. However, if that is what you're after, you really should be using something that allows for bulb ramping instead of trying to hack the aperture by disengaging a lens.

Also, you don't need to use mirror lock up, just use LiveView instead - same effect and much easier to do.

If you are creating a video, then output resolution is normally not above 2 Megapixel. Thus shooting in RAW seems like an overkill by a factor of - a lot. It may also create a problem with storing all the images required.

In some countries, mine included, for reasons of privacy, having equipment automatically photographing public places (a road is considered such a place) requires a permit, and you'll never get that without a better reason than just that you want to. What you want to do is considered equivalent to erecting a surveillance camera, and that's only allowed without a permit as long as it covers your own property only. This may not be an issue where you are, so just consider it a reason.
I saw you are in Seattle, and considering how keen US authorities are on spying on just about everyone, this is perhaps a totally moot point for you.

I shoot time lapse with my XTi. Shooting raw gives the best quality, range, and flexibility. Does increase processing time a lot. I'll shoot jpg if I want to do a quick and dirty video.

I've watched several of Richard Harrington's tips and I've not seen one that recommends disengaging the lens. As others say above shooting manual would be preferred.

I think the idea with disengaging the lens - and thus locking it into a specific aperture setting is that even in manual mode the lens goes wide open until the shot is taken and then stops down. When doing time lapse, even the smallest variation in the accuracy of this action creates a flicker in the video. I have never done time lapse, but my videographer friend does, and he uses a manual aperture lens for that reason.

MattPharmD wrote in post #16969007
....and he uses a manual aperture lens for that reason.

That makes the most sense to me. Working with a lens that is not totally locked to the camera body is simply asking for serious problems.