False metering ?

[pat3pee]

Hi,
I took some test shots with my new Canon 50mm f/1.4 lens of the same subject (flower) and distance
using the same settings ISO 800; f/2.8 same, M focus same but with shutter speed 1/250; 1/350 and 1/4000
The picture got correctly somewhat darker on the 1/350sec but a lot lighter with 1/4000sec.
Am I missing something here ? Please tell me how this could happen .

Patrik

[arith]

that is 4 stops darker, it is impossible unless the light improved by 5ev.

[Manfred M]

I don't know the fine details of the Canons, but did you turn off your automatic ISO adjustment? I had a somewhat similiar issue where the camara tried to crank up the ISO when my aperture / shutter speed did not allow for a "correct" exposure.

[herbert]

Hi Patrik,

There are a few things that could be happening. What camera are you using? Did you use Manual mode to change the shutter speed? I have interpreted your post as stating you used Manual focus but I am unclear about the exposure mode (although using a constant f2.8 would imply Manual mode).

It is possible that one or either of Canon's 'Auto lighting optimiser' or 'Safety shift' are being applied. The first affects JPEGs in camera and the second should not affect Manual mode but will apply in Av/Tv mode. A few more details on your test would help.

Also I have to ask if you used flash with one or any of the shots? If so then the camera may adjust the shutter speed to the fastest sync speed possible with your camera. This would be way below 1/4000 (probably 1/250s or 1/200s) and so the image will look much brighter than you expect.

Alex

[pat3pee]

You must be right thanks. I saw this the day after and must have used a filter and forgotten it.

[pat3pee]

Thanks for your help Alex. I use a Canon 60D, had it in Manual mode w. spot metering. Pictures taken both in RAW and jpeg with the same effect. No flash was used. I seem to be confused that I dialed in 1/4000sec which I cannot remember doing but that's what the EXIF data shows .

[pat3pee]

I don't know the fine details of the Canons, but did you turn off your automatic ISO adjustment? I had a somewhat similiar issue where the camara tried to crank up the ISO when my aperture / shutter speed did not allow for a "correct" exposure.

Well here are (attached) jpg previews of all the three photos, detective.
Rgs/Patrik

[Colin Southern]

Well here are (attached) jpg previews of all the three photos, detective.
Rgs/Patrik

Not seeing any attached images

[Dave Humphries]

Well here are (attached) jpg previews of all the three photos, detective.
Rgs/Patrik

Hi Patrik,

We don't see any images I'm afraid.

Have a look at this thread which details four different ways to display images at CiC.
HELP THREAD: How can I post images here?

Just be sure to follow all of the steps in whichever method you choose, it is a two stage process; upload the picture to somewhere, then put a link to the picture into the post - many people that have problems stop too soon and miss the second part. Even I did, which is why I wrote the instructions

Welcome to the CiC forums from ....

[pat3pee]

Sorry Colin, I'm new at this. Will make another try+

[Dave Humphries]

Hi Patrik,

Well I'm stumped too, I'm not a Canon shooter, but the sun looks to be shining in all three, all other figures are equal, so why the left hand one (with supposedly a much shorter exposure) is so much brighter is a mystery to me.

Cheers,

[William W]

I suggest this procedure:

1. Peripheral Illumination Correction

With the lens attached to the 60D, open the First Camera Menu and scroll to “Peripheral illumin. Correct.” – press “SET”
Select “Disable” – press “SET”
Close that menu.


2. Auto Lighting Optimizer

Open the Second Camera Menu and scroll to “Auto Lighting Optimizer”. – press “SET”
Select the icon on the left of the screen “OFF”. – Press “SET”


3. Bracketing

Whilst still in the Second Camera Menu, scroll to “Expo.comp./AEB”. – Press “SET”
If not already in the centre, select the AEB amount such that the bar line appears ONLY at the CENTRE POSITION. Press “SET”
Close that menu.


4.
Repeat your test ensuring that the light is constant and the same for each test exposure.

The results of this second test will confirm or not, if one or a combination of these camera Functions is the cause of your first test result.

If you are unsure of these Camera Functions and the Enable/Disable procedures, refer to the Bolded and Underlined Topics, in your 60D User Manual.

WW

[Ken MT]

I see that you are using spot metering in all three images. Can you check with the images where the exposure was taken from. Either use AF point enable in the menu, or else look in Zoombrowser. I suspect that the left image was exposed on the dark stem or dark brown brick, while the others were on various parts of the flower. Try again using evaluative metering and see if you get the same results at different shutter speeds

[William W]

Ken,

The METERING MODE and also the whole of the camera's TTL metering system would appear to be irrelevant - considering:

1. The OP stated in post #6, that MANUAL CAMERA MODE was used.
2. EXIF details, confirm that statement.


Notwithstanding those two points - the test was conducted over a period of only 2 minutes, and it is implied that the lighting did not change during that time.

WW

[Colin Southern]

Hmmm - not an April Fool's joke by any chance?

[William W]

Hmmm - not an April Fool's joke by any chance?

I have thought of that possibility.
If it is, then we will surely know: either by silence or by laughter.

WW

[herbert]

Given the use of manual mode and shooting with raw I do not know how this has happened. If the image had been pushed 4 stops in post processing then we would see noise and banding artifacts.

Try the test again but shoot at all single stop shutter speeds from your correct exposure down to your shutter limit:

1/250
1/500
1/1000
1/2000
1/4000

Perhaps you will be able to find out the shutter speed where the camera errors. If you do then repeat with all intermediate shutter speeds to see if there is a point at which the camera fails.

Hopefully you will not be able to repeat the error and you can write it off as a mistake by the camera. If the error is repeatable then you may have a camera fault, or a combination of settings with a behaviour which we are not aware of.

Alex

[William W]

Given the use of manual mode and shooting with raw I do not know how this has happened.

Hmm, maybe I am misunderstanding the sandwich of three Images which was posted as the support document.
I understood those three images to be the JPEG files, SOOC?


WW

[pat3pee]

Yes and showing the similar camera settings

[pat3pee]

Alex,
I have done all this now a couple of times without any aberration so it must have been a one-off fluke.
Thanks guys