Metering - Horrible underexposure

Started Dec 14, 2009 | Discussions
jhass1 Junior Member • Posts: 31
Metering - Horrible underexposure

I have a new (to me - it's second-hand) 5d on which I thought the LCD had failed - actually just HUGE underexposure. I have tried:
Firmware update to 1.1.1.
Resetting everything
Formatting various CF cards (which work in other Canon 40ds)
Changing Lens

Nothing - the underexposure is AT LEAST 5 stops but the funny thing is that the metering does actually change in response to light but is badly out - I cannot get even vaguely usable images at any ISO. HELP!!

Steven Noyes Forum Pro • Posts: 12,372
Do you EC set? Sample images with EXIF intact.

These always help.

Steven

dswcamera Senior Member • Posts: 1,676
Interested & like to help but need more details

At this point all we know is the exposure appears way off to you but nothing of the particulars

What were the shooting situations, indoors, outdoors
Av or Tv modes.

Have you put it in manual mode, moved the camera through various lighting and watched the light meter response?
What ISO are you using
Is this flash or natural lighting.

Show us some examples too.
Dan
--
'A bad idea in search of a good cause is..
just a bad idea' ... me

foxikk
foxikk Regular Member • Posts: 169
Re: Interested & like to help but need more details

did you try removing front Lens Cover ?

But seriously did u try taking picture with AUTO mode and see if u get correct exposure. If not then it might be metering sensor

OP jhass1 Junior Member • Posts: 31
Re: Interested & like to help but need more details

Thanks - I've tried everything in all modes. I'm not sure images will help - they are LITERALLY dark grey unless I shoot directly into a lightbulb or overexpose in "M" by many many stops. At the moment I have removed both batteries and have left the body for 1 hour - just about to replace batteries and check again. Would sample images help anyone diagnose? EXIF? btw all shot in RAW (apart from AUTO mode). Anyone know any tricks on resetting metering - I heard someone say that on SONYs if you switch on at the same time as holding two buttons down you get a low level reboot (a la ipod).

OP jhass1 Junior Member • Posts: 31
Re: Do you EC set? Sample images with EXIF intact.

So the batteries being out for 1 hour didn't work - the date needed reset but the last settings on camera were retained. It also looks like the camera is setting a "base" reading for each ISO/mode/Speed/Stop combo and THAT DOESN'T CHANGE even moving from high light source (light bulb) to dark corner (this is all inside shooting but the effect was first noticed outside).

Here an example table mode AV metering Eval:

ISO
100 (f4.0) 1/1250
400 (f4.0) 1/4000
800 (f4.0) 1/8000

Partial metering slightly slower (1/1000 at ISO 100 f4.0)
Spot - same as Partial
Centre - slightly faster (1/1600 at ISO 100 f4.0)

The reverse (in TV mode) holds true, i.e. when the speed above is selected then f4.0 is the result.

Histograms show a VERY narrow (maybe 2-4%) cluster on left.

So my conclusion is that there is a random default setting selected based on the mode/metering/ISO combo and that the meter sensor is whacked. Any thoughts?

rolandsilva Regular Member • Posts: 428
Re: Interested & like to help but need more details

if you have it in auto mode and it is consistent you may have actually set the exposure over ride in program aperature or shutter priority you can have the camera shoot over or under by moving I think it is the back wheel, you will see the exposure compensation amount show on the top lcd. I did this once by accident in aperature priority and could not figure out why everything was underexposed by a stop.

OP jhass1 Junior Member • Posts: 31
Re: Interested & like to help but need more details

sadly not that simple but thanks. The underexposure is SO much that I thought the LCD screen was gone!

foxikk
foxikk Regular Member • Posts: 169
Re: Interested & like to help but need more details

camera has to go to service and you can only try with M mode for now

dgovoni Contributing Member • Posts: 915
I assume you understand the 18% reflectance rule (medium tone)?

All camera meters are calibrated to correctly expose for medium tone. So to correctly test whether this meter is working, go buy a gray card and with front lighting on the card, set exposure to zero (middle) of the meter as you see it. The resulting image will look to have the same tone as the grey card. If not, there is a meter problem or possibly something with the shutter.

-- hide signature --

dennis

dgovoni Contributing Member • Posts: 915
This might help
Victor Engel Forum Pro • Posts: 18,487
Re: Metering - Horrible underexposure

Have you tried removing your linear polarizer? Actually, I'd think that would have the opposite effect -- just brainstorming here.
--

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Steven Noyes Forum Pro • Posts: 12,372
Sounds like a dead meter.

Assuming you know how to use everything, the meter will need serviced.

Steven

Kiwi_Rick Junior Member • Posts: 26
Try A Basic Test

To separate metering issues from other possibilities, I suggest that you try taking a picture in Manual mode at ISO 100, in full sunlight at 1/125th and F16. This should get you an image that is within a stop or so of correct exposure.

If you still get a dark image, then there is a fault with the camera, possibly in the sensor circuitry, and I would send the camera for service.

Kiwi_Rick Junior Member • Posts: 26
Re: Try A Basic Test - More

Thinking a bit more about this:

1. If the manual exposure turns out approximately correctly, then you may have a metering problem. Otherwise, if images are still dark, then :

2. You could try with a different lens, in case there is a lens problem

3. Or maybe the shutter is at fault

4. Or as I said before, a sensor or electronics issue

Regardless, it sounds like service is your best option. Let us know the outcome !

PicOne
PicOne Veteran Member • Posts: 6,931
Where/who did you buy it from used?

and have you asked him/them/it about this issue?

-- hide signature --

'Everything in photography boils down to what's sharp and what's fuzzy.'
-Gaylord Herron

PawelWoj Senior Member • Posts: 1,040
Re: Do you EC set? Sample images with EXIF intact.

Is the exposure needle at the center? you may have to turn the big dial to get it to the middle cause the previous owner might have had the Exposure compensated.

To do this you have to turn the cameras viewfinder info on so half press the focus , then turn the big DIAL to the center in the viewfinder.

jhass1 wrote:

So the batteries being out for 1 hour didn't work - the date needed reset but the last settings on camera were retained. It also looks like the camera is setting a "base" reading for each ISO/mode/Speed/Stop combo and THAT DOESN'T CHANGE even moving from high light source (light bulb) to dark corner (this is all inside shooting but the effect was first noticed outside).

Here an example table mode AV metering Eval:

ISO
100 (f4.0) 1/1250
400 (f4.0) 1/4000
800 (f4.0) 1/8000

Partial metering slightly slower (1/1000 at ISO 100 f4.0)
Spot - same as Partial
Centre - slightly faster (1/1600 at ISO 100 f4.0)

The reverse (in TV mode) holds true, i.e. when the speed above is selected then f4.0 is the result.

Histograms show a VERY narrow (maybe 2-4%) cluster on left.

So my conclusion is that there is a random default setting selected based on the mode/metering/ISO combo and that the meter sensor is whacked. Any thoughts?

OP jhass1 Junior Member • Posts: 31
Re: Where/who did you buy it from used?

Yes, not sure he gets it. Anyway I have finally bowed to the inevitable and have sent it to Canon for proper evaluation and (hopefully) fixing.

OP jhass1 Junior Member • Posts: 31
Re: Try A Basic Test - More

In case you're still interested... Canon serviced it and said that they "Readjust exposure and shutter speed to standard. Clean sensor". Sent it back. It appeared fine taking an indoor shot at high ISO so I was delighted. Next morning took and outside shot. Also OK. Took another - not great and in AV mode it had selected the SAME speed despite a significantly darker scene. So I played around and it looks like the meter is selecting an appropriate exposure at the FIRST shot and then just not seeing any change in light as I move from indoors to out, or vice versa. In other words they have done nothing and clearly not tested what they thought they had done. It's all packed up ready to go in the post back to them on Monday - ho hum what a painful saga this is turning out to be. Wish I could find somewhere selling unused old stock of the Mark 1.

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