Sony A7/A7R light leaks - Roger Cicala of LensRentals weighs in

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posted Tuesday, March 11, 2014 at 3:37 PM EST

 
 

Another day, another story about Sony A7 light leaks...

Honestly, we're about coming to the end of our coverage on this topic, as it's a complete non-issue for the vast majority of photographers, and we're pretty close to having beat it to death. We have one more hopefully definitive piece of our own coming on the subject, but in the meantime, felt we had to share the findings of our friend Roger Cicala, from LensRentals.

Roger and his intrepid team not only did a much more meticulous leak-hunt than any to date, in the process checking several samples each of the A7 and A7R, but, as is his wont, also disassembled one of the cameras to get at the root causes of the issue, and develop some effective fixes.

See Roger's writeup for all the details, but here's the gist of it.

First and foremost, though, Roger begins with this observation: "Let me think this through. If you shoot a 30 second exposure at ISO 25,000 into the sun or with a studio strobe aimed at the camera, you get a light leak. I do that . . . let me think . . .  never. And this isn’t my first rodeo. I’ve noticed there are light leaks in lots of cameras if you look for them, and most of them were apparent without jumping through all the hoops it took to produce them on the A7r."

As we demonstrated ourselves in yesterday's article, while several cameras we tested didn't leak light at all, some do, even some fairly high-end models. However, all of the leakers, including the A7, leaked light at levels that would only be an issue for people doing very long exposures under daylight conditions, using very high-density ND filters to achieve the desired exposure durations.

With that as background, Roger's first step was to do a point-by-point search around the camera, to see exactly where the light leaks were coming from. To do this, he and his team used a high-intensity fiber-optic illuminator from one of their microscopes:

 
Roger and the LensRentals team used a high-intensity fiber-optic light source to determine exactly where the A7 light leaks were coming from

Interestingly, some of their shots showed light leaking in the upper left-hand side of the frame, vs just the upper-right, as many have reported on the Internet. This validated our own full-sun tests, which showed light spread across more of the frame than others have found.

 
Roger and team found light leaking onto the left side of the image, duplicating some of our own results

Here's a brief summary of the LensRental findings:

  • We tested several A7rs and several A7s and all were the same, so it’s simply a design issue, not a batch of defective cameras.
  • The light leak occurs with the body cap in place, but is more severe with a 35 f/2.8 Sony lens mounted instead of the body cap. 
  • The leak is worst when the light is shined onto the lens-release button area. It is also bad when the light shines onto the lower left quadrant of the lens mount, and directly above the lens mount. Other areas either didn’t leak or showed only a thin line that was far less pronounced than these areas. 
  • Wrapping something around the lens mount stopped the left side leaks, but not the leaks around the lens-release button.

This was very interesting; it seems likely that the source of the broader leak we found when the camera was pointed directly at the sun was the lens-release button. Others have been focusing (no pun intended ;-) on the lens flange itself, which might explain why the streak in the upper-right was a more common artifact. Pointing the camera directly at the sun is something you'd probably not do, even if you were a daylight long-exposure enthusiast, which possibly explains why others haven't seen the broader pattern yet.

 
Here are the three locations on the A7/A7R body where LensRentals found light leakage. The lens-release button at lower left was the most serious leak by far.

 

 
Roger and company tried masking-off their high-intensity illuminator, so it would only shine onto the lens release button itself, and were surprised that they could actually see the light leak visually. (Note that this is a very high-intensity light source, you'd be hard-pressed to see this with a flashlight or ordinary incandescent lamp.)

They tried a couple of quick fixes, as seen below:

 
One fix Roger and team applied was to remove the lens-mount flange, and carefully apply some black electrical tape to its backside and periphery. While this worked very well, note that this is NOT recommended, as it will almost certainly void your warranty. The safe approach is to just use an elastic "scrunchy" hair-band around the base of the lens to block light from this area.

 

 
The most critical fix was to block light around the lens-release button. Here, a small piece of electrical tape blocked the light, while still allowing normal operation of the release button. (A note from my own personal experience here: It's very worthwhile to spend the money on some good 3M-brand electrical tape. The adhesive on 3M tape seems to hold up fine for years, while that on off-brand tape can turn gummy and messy in a surprisingly short time.)

Kudos to the LensRentals team for having done such a meticulous job of identifying the specific sources of the A7/A7R's light leaks. As we've said several times now, and now with concurrence from Roger Cicala, these light leaks really don't look like anything that would remotely affect 99.9% of photographers out there. If you're into very long exposures with dense ND filters under daylight conditions, you'll probably want to put a hair-band scrunchy around the base of the lens and a bit of electrical tape over the lens-release button. The rest of us can almost certainly relax.

Stay tuned for our own third and final look at the issue in the next day or two, once our own A7 sample makes its way back to IRHQ. In that piece, we'll look at some real-world examples, to determine at just what exposure and ambient light level the leaks become apparent. Based on everything we've seen so far, we're betting it will be well outside any range most photographers would ever encounter.

Check out our final conclusions here.