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Posts: 2
Registered: ‎10-02-2013

5d Mark III - Metering Underexposed

So first off, I apologize as I think I've seen a similar thread here but I can't find it anymore!

 

I purchased a 5d Mark III as an upgrade from my 7d a couple of weeks ago and, although I am happy, there is one main issue that is bothering me.

 

When I meter a "perfect" exposure, the camera is delivering about a full stop UNDER that.

 

My normal settings are; 

Shoot in M

Center focus point

Spot metering

AI Servo.

 

 

I generally shoot 2/3 over anyway, and find that I'm needing to now shoot at least 1 2/3 over to get the same result as my 7d. In addition to that, I'm getting a noticeable vignette in lower (but even/consistent) light situations.

 

I have tried all the different metering options, including variations on the focus points. I have done a full factory reset and the issue is consistent across all my lenses. 

 

Any ideas?

Esteemed Contributor
Posts: 3,805
Registered: ‎06-11-2013

Re: 5d Mark III - Metering Underexposed

I'm wondering how you're evaluating the accuracy of the meter.  All of my cameras are extremely accurate _if_ I use a gray card to test them.  But that's because the "gray card" provides a known level of reflectivity.  

 

The meter in the camera is a "reflected light" meter.  An all white target will give a different reading than an all black target even if both targets are in identical lighting - because white reflects more light than black.  

 

Spot metering is, of course, sensitive to the point you choose for the target.  You would need to make sure both cameras are not just taking photos of the same subject in the same light, but would also need to be particularly careful to make sure that the very point that your cross hairs are on for the spot focus are the same.

 

I considered that you may have altered the exposure compensation, but that's ignored when shooting in manual mode so I don't think that's it.

 

One more thing... when you "meter" an exposure, is it that both cameras report different readings, or do they report the same metering but the 5D III turns out darker?  I'm just trying to narrow down the issue.

 

Tim Campbell
5D III, 5D IV, 60Da
New Contributor
Posts: 2
Registered: ‎10-02-2013

Re: 5d Mark III - Metering Underexposed

Thanks for the response!

 

I just did some additional test shots to answer your question more accurately.

 

I shot a grey card under tungsten light at ISO 4000, 2.8, with a 50mm 1.4. I shot the same image with both cameras set up exactly the same, and the 5dm3 is, in that shot, roughly 2/3rds underexposed.

 

I'm really baffled. 

 

ps. I notice you use the 60Da. Never spoken to an owner. Do you love it? I am starting to really enjoy astrophotography so that unit is interesting to me. Its pretty much geared towards that one purpose yes?

Esteemed Contributor
Posts: 3,805
Registered: ‎06-11-2013

Re: 5d Mark III - Metering Underexposed


@rjs1981 wrote:

Thanks for the response!

 

I just did some additional test shots to answer your question more accurately.

 

I shot a grey card under tungsten light at ISO 4000, 2.8, with a 50mm 1.4. I shot the same image with both cameras set up exactly the same, and the 5dm3 is, in that shot, roughly 2/3rds underexposed.

 

I'm really baffled. 

 

ps. I notice you use the 60Da. Never spoken to an owner. Do you love it? I am starting to really enjoy astrophotography so that unit is interesting to me. Its pretty much geared towards that one purpose yes?


You don't, by chance, happen to own an incident light meter to determine which camera is actually telling the truth do you? 

 

As you are shooting in "M" according to your post, the exposure compensation is ignored (it's used to P, Tv, or Av modes... but not M).  It's the only setting I can think of that would cause the camera to createa a different exposure.

 

So barring that, it seems one of your cameras is having a problem.   I once had someone tell me that their Canon 5D II and Canon 5D III were giving different exposures... but I own two Sekonic incident light meters and three Canon bodies.... so I tested the light with both Sekonic incident meters, then tested my bodies pointed at the same gray card and all agreed on the exposure.

 

But it sounds like you've done some reasonable testing to make sure the exposures *should* be the same... and yet they aren't.  It seems reasonable that it points to a problem with one of the cameras.  I can tell you that my own 5D III body (and I also own a 5D II body) are metering accurately so I don't think there's a 5D III metering problem per se, but you may have a individual body with an issue.

 

 

 

As for the 60Da... I'm quite pleased with this camera.  So here's the story.

 

I belong to a fairly large astronomy club in the area.  I'm going to guess there are about 160 members.  Of those... probably about 20% are fairly seriosu imagers.  A few owned the old Canon 20Da (the first astro camera Canon sold).  Many members own modified and unmodified Rebel bodies as well.  But when Canon released the 60Da, several members took notice and bought one.  

 

So one day I'm at a friend's house and the previous night another club member was at his private observatory with his 60Da and took a photo of the whirlpool galaxy (M51).  I was looking at the EXIF data for the exposure.  At the time I did not own a 60Da... but I did have the 5D II (I did not yet have the 5D III).  I took the _same_ exposure (ISO & shutter time) with my camera using the identical scope in the same observatory for the same object.  

 

At the end of my exposure, I got almost nothing.

 

I doubled the exposure. 

 

I could see a hint of the galaxy... but mostly nothing.

 

I tripled the exposure.

 

Now I was starting to see the hints of the galaxy... but nowhere even remotely close to what the 60Da had captured.   (and I'm using a 5D II which blows the doors off the 60D when it comes to ISO performance.)

 

The following day I ordered a 60Da.

 

Human eyes are a bit wonky... we are "most" sensitive to greens because they are pretty much smack in the middle of the visible spectrum (which runs from 400nm to 700nm wavelengths).  We are less sensitive to blues and reds.  Traditional cameras compensate for this in several ways... rather than "truthfully" collecting light, the Bayer mask is already stacked to double the green reception vs. the blue or red.  But even the filters inside the camera have a slow ramp up to block the IR.  The "IR" filter actually starts to block the spectrum gently even as low as around 500-550nm.   It ramps up gradually as it approaches 700nm.  

 

90% of the universe is composed of hydrogen atoms.  Atoms give off light at very specific wavelengths as their electrons jump from one shell to anotther.  For hydrogen, it's the Ballmer series where the dominant light is at 656.28nm (Hydrogen alpha wavelength), then hydrogen beta, gamma and delta... but those are cyan, and a few shades of violet and safely sharter wavelengths then what a terrerestrial camera IR filter blocks.  It's mostly the Ha which is a problem.  

 

The 60Da is at least 3x more sensitive to Ha (and possibly closer to 5x more sensitive) as compared to a non-modified terrestrial DSLR cameras.    The result is that not only do you get more reds (the Ha is a fire-engine red color), but overall you get much shorter exposure times to capture the same image.

 

There are several companies which make high end dedicated astro-imaging CCD cameras... SBIG (Santa Barbara Imaging Group), Finger Lakes, Apogee, etc.  These are typically monochrome cameras with peltier cooling systems that can chill the CCD considerable colder than ambient temps (becaue there's a relationship between physical temps and noise), have incredible well-depth (basically a measure of dynamic range), and fitler wheels.  Since a monochrome camera does not have a bayer mask, the cameras are much more sensitive to light -- but they can't see "color".  To compensate, a filter wheel rotates in a "red" filter, "blue" filter, "green" filter, and usually a "luminance" filter.  They may also use special narrowband filters to pick up Ha, Hb, O III, etc.   They take numerous images in each part of the spectrum and them merge them to create color image.  These cameras tend to be expensive.    I sure would love to own an SBIG STX-16803 and filter wheel but it's the better part of $12,000!  

 

The 60Da has been working quite nicely so far - a good workhorse and I've put it to use numerous times capturing images for hours on end.

 

Here's an image taken by my 60Da.  This is based on 16 combined "light" images of 4 minutes each of the Dumbbell nebula  (Messier 27).  I also took 8 "darks".  What I did _not_ take were any "flats" or "bias" images and it shows.  You can see the obvious vignetting caused by the telescope ("flat" images would have allowed my software to compensate for this.)   The red colors you see in this image are Hydrogen atoms giving off light in Hydrogen alpha wavelength.  Without a modified camera, you get red... but not nearly as much.

 

BTW... in fairness I should mention that I'm getting pretty good at image "acquisition" in astrophotography... but I have a lot of learning to do when it comes to image "processing" for astrophotography.  Most of my club members blow me away (even using the same camera that I use) but I am learning quickly.

 

Dumbell Nebula.jpg

 

Tim Campbell
5D III, 5D IV, 60Da
Occasional Contributor
Posts: 7
Registered: ‎06-21-2014

Re: 5d Mark III - Metering Underexposed

I am interested to hear the responses, as I have the exact problem, and coming from a 7d, which I still have. With my 7d, I have metering mode set to evaluative mode, and chose single AF POINTS , whoever AF point I chose is the active metering point, and is always an accurate meter reading. With the 5d Mkiii, not so much. Same as you, when I try to meter from the chosen AF point, the actual shot comes out very underexposed. I am needing to know exactly what and where I should be metering. With the 7d I chose my AF point, where I want the subject's eyes, and the 7d meters from that spot. With the 5d Mkiii, I am still struggling to find how and where I meter to meter for eyes, do I have to meter using spot meter and direct center point over eyes, then recompose camera with subjects eyes at the chosen AF point?
Occasional Contributor
Posts: 18
Registered: ‎08-01-2014

Re: 5d Mark III - Metering Underexposed

I too have complained about underexposure with my new Mk3 especially vs that of my Mk2.  I feel that all of my shots are appear nicer with some added exposure.  The more I searched the more I found this appears to be an epidemic of sorts, as many people are on forums with the same complaint.  When I had my Mk3 in for the light leak repair, I asked them to check exposure and they claimed it was ok - however I suspect they didn't even check because they missed other things on the work order as well (not the first time I had problems with Canon Missisauga so it's easy to be suspicious).   Since it's not just me I'd wager a guess that there is a definate concern here that the product has been experiencing problems either by design or some failure after purchase.  I would really like it if some Canon personel could pipe in and comment here. 

 

However, I can offer a scenario that I have not acted on testing yet.  It is possible that Canon feels either due to sensor design or by firmware that the 5D3 should meter more to the left as compared to most bodies.  Possibly to deal with noise or highlight/shadows detail.  I can't really see why and talk on the internet would not support this possibility.  It is also possible that the 5D3 does not respond well across the whole colour/exposure spectrum making the shots look more lifeless than other shots even though the exposure as a whole is correct? 

 

Either way, requires Canon to get off their high chairs and quit expecting that their name alone is going to keep them in business because the world is starting to get dissapointed with the product lately.  It appears Sony, Nikon and Panasonic are all starting to walk by.  The 5D3 is a nice body but for the price I should've sold off my glass and bought the D800.

Occasional Contributor
Posts: 18
Registered: ‎08-01-2014

Re: 5d Mark III - Metering Underexposed

In reading deeper into this forum, I discovered another thread that appears to address this issue which I am interested in testing as soon as I pull out my camera.  Seems to have worked for 2 people who followed that thread, I'd be really interested to hear if it works for you.   It reads as follows:

 

  

 

Dgtl_nm8r,

 

There was a serivce advisory for the EOS 5D Mark III, but it was not related to the issue you are experiencing.  As a first step towards resolving this issue, we suggest that you restore the camera's default settings.  You can reset to the factory settings by following the procedure below: 

 

  1. Press the MENU button.
  2. Select the [Tools #4] tab.
  3. Select [Clear All Camera Settings].
  4. Press the SET button.
  5. Select [OK].
  6. Press the SET button.

 

Esteemed Contributor
Posts: 3,805
Registered: ‎06-11-2013

Re: 5d Mark III - Metering Underexposed

I did notice one comment in this thread that looks like a misunderstanding. 

 

When you use spot metering on a Canon camera (this is true of all the models I've owned and I've yet to encounter an exception but haven't checked all bodies)... the "spot" is always at the center of the frame... not at the selected AF point.

 

The camera does support metering lock... you can point to the spot you'd like to meter, lock in the metering read, re-compose and focus to what you want to shoot.

 

When using spot metering but wanting to focus on some location OTHER than the center, do the following:

 

1)  With camera in spot metering mode, point the camera at the target you'd like to use for metering purposes -- taking care to insure that the metering point is in the CENTER of the frame.  

 

2)  Half-press the shutter button to cause the camera to meter and focus.

 

3)  Press the asterisk (*) button on the back of the camera (upper right corner on the back).  This will "lock" the meter reading. The camera will display an asterisk through the viewfinder window as well as on the rear LCD to indicate the meter reading has been locked.  (the lock will automatically release if you don't press anything for several seconds)

 

4)  Re-compose the frame and use the select AF point to focus the shot as you want.  As long as you don't wait so long that the asterisk disappears from the display, your metering is still locked to your previous subject.

 

Now you can take the shot -- with metering exposed to one point, but AF focused to some other point.

 

The metering lock will be cleared once you take the shot.  It will also be cleared if you don't use any camera controls for a few seconds.  If you don't want to take the shot or wait, you can force it to clear immediately by pressing the AF point selection button (even if you don't change the selected AF point).

 

Tim Campbell
5D III, 5D IV, 60Da
Occasional Contributor
Posts: 7
Registered: ‎06-21-2014

Re: 5d Mark III - Metering Underexposed

Correct on the spot metering, but in my 7d in Evaluative metering mode, the chosen AF point is the active metering point. On the 5D mkiii it doesn't appear to be that way, and I'm still having a heck of a time nailing the metering on the 5D!! Very frustrating!! Any tips? Even when I have spot, meter of the center point, set exposure( in manual mode) and the recompose, I am not getting accurate readings! Almost always underexposed, also using other metering modes, same thing! What am I missing and why!!
VIP
Posts: 10,993
Registered: ‎12-07-2012

Re: 5d Mark III - Metering Underexposed

Beside Tim, a great guy to know is Tom Martinez.  His blog is http://tomjmartinez.blogspot.com/

Is an accomplished astro-photographer and willing to answer questions.

 

If I were you concerning the exposure issues with the 5D Mk III, is try the same test with evaluative metering.  Spot metering can be problematic at times.

EOS 1DX and 1D Mk IV, even less and less other stuff.
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