The Light Leak Issue

[TrumpetPower!]

... it just doesn’t appear there is an issue to me.

Wrong.  It's a HUGE issue for anyone who's favorite photographic subject is the inside of a lens cap!!!

All sarcasm aside... does anyone not see how this could be a serious issue for astrophotographers? 

If you are using a headlamp or the LCD backlight to set your exposure for a night sky capture, you could be in serious trouble.  I'll be doing some tests tonight and will follow-up tomorrow.

I fear the 5D3 may not be suited for astrophotography at all if this problem affects nighttime exposures.

I've not done any astrophotography, but I was under the impression that the onboard meter is perfectly useless for such work. Or any meter, for that matter -- I thought the serious stuff was all done either from well-established exposure charts or by stacking multiple exposures....

b&

[cinema-dslr]

 could it be that they switched the amber backlight position from the right(7d) to the left next to the mirorbox?

when you look at the lcd at an angle you can make out the led.
i believe that one side of the lcd is mirrored off to reflect the backlight back.
the ledside isn't so sunlight can sliptrough and the ledlight itself will have a more profound effect when placed next to the mirror box

can someone check the position of the backlight led on the markIII?

[Tov]

Perhaps the reason that this shows up with the cap on is because the sensor is actually really really sensitive, more so than on older models, and that is why it seems to show up on the high end gear only.
IE: The same minor leaks as on all gear, but now the sensor can see it.

Boom.

Good one.
Already people are seeing more vignetting on there lenses, probably also due to the sensor.
I still have old stuff, lucky me.
 
very juicy picture btw.

[Fleetie]

... it just doesn’t appear there is an issue to me.

Wrong.  It's a HUGE issue for anyone who's favorite photographic subject is the inside of a lens cap!!!

All sarcasm aside... does anyone not see how this could be a serious issue for astrophotographers? 

If you are using a headlamp or the LCD backlight to set your exposure for a night sky capture, you could be in serious trouble.  I'll be doing some tests tonight and will follow-up tomorrow.

I fear the 5D3 may not be suited for astrophotography at all if this problem affects nighttime exposures.

Erm, no.

Because you would NOT rely on the camera's idea of what is correct exposure when doing astrophotography. Because if you did, the camera would seek to make the picture's lightness similar to that for normal photography.

You simply don't use the camera's exposure system when photographing star fields, because the overwhelming majority of the field is near-black.

You go to manual, or bulb.

Unless you're doing high-magnification photos of the Moon or other frame-filling objects, in which case you're now doing daylight photography, and basically, the terrestrial sunlit "Sunny f/16" rule applies.

Also, you're unlikely to be using headlights or bright torches anyway when engaged in astrophotography, because doing so would destroy your night vision.

BUT, please do report back your findings, because it will be a useful data point.

The 5D3 is the most light-sensitive/noise-free DSLR that exists in a conventional-size (non-integrated-grip) body at the present time, AFAIK.

So it would seem, it's the best such DSLR for astrophotography. (Possibly barring the 60DA, but even then I suspect the 5d3 wins on low-light performance.)

[altenae]

Already people are seeing more vignetting on there lenses, probably also due to the sensor.

?
Maybe because they switched to a Full Frame !
Same vignetting on my 5D mark iii as on the 1ds/5d mark ii.

[Tov]

Already people are seeing more vignetting on there lenses, probably also due to the sensor.

?
Maybe because they switched to a Full Frame !
Same vignetting on my 5D mark iii as on the 1ds/5d mark ii.

I was trying to be sarcastic.

[altenae]

Read this elsewhere.

Read it and think about it.
This leak thing with cap on is BS.


These lens cap on tests are ludicrous beyond belief.
They involve light levels far beyond the meter's range of operation. The meter is designed to produce an image that is 18% grey. Does anyone seriously think that the meter reading in these tests, with or without the LCD light, are registering 18% grey.

Add to that the fact that the EV scale is non-linear and it's hard to see how a rational, informed person could get so hysterical about this. The quantity of light required to shift exposure by 1 stop at these levels becomes a tiny fraction of a stop at real exposure levels - probably less light than leaks into the viewfinder past your eye - and much much less if you happen to look through the viewfinder wearing glasses.

[altenae]

Already people are seeing more vignetting on there lenses, probably also due to the sensor.

?
Maybe because they switched to a Full Frame !
Same vignetting on my 5D mark iii as on the 1ds/5d mark ii.

I was trying to be sarcastic.

 

[JR]

Thanks for all the test Graig.  I would assume Canon would get back to you with their official story on this issue?  Or have you shared with them at all?  Curious...

[Mt Spokane Photography]

... it just doesn’t appear there is an issue to me.

Wrong.  It's a HUGE issue for anyone who's favorite photographic subject is the inside of a lens cap!!!

All sarcasm aside... does anyone not see how this could be a serious issue for astrophotographers? 

If you are using a headlamp or the LCD backlight to set your exposure for a night sky capture, you could be in serious trouble.  I'll be doing some tests tonight and will follow-up tomorrow.

I fear the 5D3 may not be suited for astrophotography at all if this problem affects nighttime exposures.

If you turn a bright light on during a long exposure, you will have 10,000 more times light leaking thru the lens than the lcd.  Set your exposure before opening the shutter, in fact, I don't believe you can set a different exposure once the shutter is open.  Try that and let us know how it works.
 
BTW, last evening, I had tried some of the same tests that Craig did and found the same results.  It is very difficult to block all light from entering the viewfinder, holding it to your eye lets enough light in to change the exposure slightly as you move from shadows to direct sunlight.  However, even with a very bright led flashlight, and even the bright sun on the top LCD, I could not cause a change in exposure when the viewfinder was totally blocked.
 
I seem to recall someone doing the same test on the 5D MK II 4 years ago, it had no effect on mine the past 4 years, and does not affect exposures on my 5D MK III.

[NormanBates]

so is the light leak "only to the light meter" or "to the sensor too"?
because I can live happily with the former, but the later would be a killer (I like stars timelapses)

[bp]

Thanks for testing so thoroughly Craig.  Basically the same results I found when trying to "leak" into an actual lens-cap-off exposure.  I just can't force myself to get concerned over P-mode shots of the back of the lens, because I only do that when I'm REALLY drunk

[bp]

Perhaps the reason that this shows up with the cap on is because the sensor is actually really really sensitive, more so than on older models, and that is why it seems to show up on the high end gear only.
IE: The same minor leaks as on all gear, but now the sensor can see it.

Boom.

Actually... this is probably the best explanation I've heard so far.  The 5D3 does seem to be MUCH more sensitive to dark situations than any other body I've ever had the pleasure of trying.  I'd be very curious to see if the 1DX also does the same thing in idiotic lens-cap-on tests.

[dilbert]

Once I placed the black fabric over the viewfinder instead of my thumb, the variance in exposure decreased in direct sunlight. However it was still present. Out of direct sunlight, the camera metered 10 seconds, in the direct sunlight the camera metered 1 second.

If a photograph gets taken and is exposed for 10 seconds, is it all black?

Does the metering problem happen if the mirror is up and metering is being done with the cap on using live view?

[Stephen Melvin]

All sarcasm aside... does anyone not see how this could be a serious issue for astrophotographers? 

If you are using a headlamp or the LCD backlight to set your exposure for a night sky capture, you could be in serious trouble.  I'll be doing some tests tonight and will follow-up tomorrow.

I fear the 5D3 may not be suited for astrophotography at all if this problem affects nighttime exposures.

The only thing this appears to affect is the meter; it doesn't affect the exposure at all. I just don't see how this is going to be of any relevance. Do you really meter the night sky? Or do you take a test shot and see what it looks like? For that matter, with experience, I'd expect the exposure to be known and consistent.