larryepage Loc: North Texas area

I love the various automatic metering modes on my cameras. I even use Program mode quite a bit in order to avoid extreme choices of either aperture or shutter speed. I'm not a big user (almost never, actually) of Auto ISO. Too dangerous.

BUT...I've learned that using any sort of automatic exposure control for stage productions can be a recipe for disaster. Dynamic range is just too great, and there are way too many "contrast zones," where dissimilar luminosity levels are present side by side. Average, Matrix, or even Center-weighted metering are better than Spot, but my consistently best results have come from a completely different approach.

Stage lighting levels, at least within a scene, rarely change much if any at all. It is almost always better to switch to manual, choose a suitable shutter speed, then adjust the aperture for proper exposure. Manually adjust ISO if necessary. Verify by using the rear display. The histogram may lie to you just like your meter may lie to you. Highlights are going to be in whoever you are photographing. If they are OK, highlights will be OK. I know that there are those who will tell you never to be concerned about what you see on the rear monitor, but your best option is to tell those folks thanks, but go and push a chain down the street. And yes...you will have to learn to interpret what you are seeing when you look at images on your rear display.

In your situation, it is easy to see that the lead dancer has moved from the side to the center between the two shots. Her white skirt and generally light outfit have caused the meter to instruct the camera to reduce exposure, just like it did. This is exactly the sort of mischief that will be eliminated by using constant exposure...no exposure change at all was needed between your two images. Nor was the reported EC of -2 needed for either image

CHG_CANON Loc: the Windy City

If the AF point was anywhere other than the nearest dancer in the brighter, higher ISO-image, that likely explains entirely the differing results with spot metering.

SalvageDiver Loc: Huntington Beach CA

Assuming the spot metering is in the center of the image, then you can see that the spot was on two different part of the image that were illuminated differenty. The spot in the first image, iso2500, was on a dark illuminated section of the image, thus the camera tried to increase image brightness to compensate. In the second image, ISO800, the spot was on the dancers dress where there was more illumination, thus the lower ISO.

It's just a difference in where the spot metering was taking its sample from.

It doesn't appear to be a camera problem at all.

(Download)

MJPerini

Why Spot metering? and why EC-2? Given the results it is almost self explanatory.....
What I mean is there appears to be one light for all the dancers placed relatively close with no modification.(Front dancer is much brighter)
I can't tell if that is a lamp in the background, or a reflection of the main light in a mirror
You have a scene with high contrast, and lots of light fall off from front to back, and since you are standing in a place that shows the reflection of the light in a mirror, (or if it is a lamp in the scene keeping it near the center of the frame) that is also throwing off exposure. If you had stepped to the side the bright reflection would be gone.(or minimized the lamp)
Also, why auto ISO, why not just do a test shot to find a high enough ISO that will work for the scene (from a spot that does not include a reflection of the main light.
This is not an easy picture to get right, you are relatively close, and at f/1.8 in a scene that has both depth and movement. In the first picture you focused one the second dancer, leaving the larger brighter first dancer out of focus. It is a very high contrast scene (especially with the light in the picture)
I am not picking on you here, this is a difficult picture to get right.
In any event there is probably nothing wrong with your camera.
This is like theatrical photography, no flash allowed, and lighting that makes one person far brighter than the rest.
What most people do there is isolate with a longer lens so you can get both focus and exposure right one or two performers at a time.
I hope this helps a bit.

joecichjr Loc: Chicago S. Suburbs, Illinois, USA

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

There is no normal variance when it comes to setting the ISO parameters. Everyone is different. You might choose 100-400, or 100-800, and the amount of variance differs from manufacture to manufacture.
My personal preference is to use the smallest ISO possible. That is why I do not let the camera choose anything especially when it comes to exposures. I am and will always be an ALL manual guy.
I do the thinking, I leave nothing up to a electrical marvel.
My best advise would be to set your ISO variance to the lowest possible settings.

Nalu Loc: Southern Arizona

From the dialogue, it seems as though the camera is working as designed. The question would be, why shoot auto ISO in this case with a static source of light? Shoot manual and take the variability out.

Bultaco Loc: Aiken, SC

davidrb Loc: Half way there on the 45th Parallel

There are differences in models but my 1 Dx does not like spot metering for many instances. Some shooting buddies feel the spot is too sensitive for indoor work. The slightest change in sunlight will greatly effect the meter. I have stopped using it and am liking the results. The 1 Dx series is an entirely different camera from all other Canons. You have set yours fairly tightly and yes, in AUTO mode ISO will vary widely. Are you certain your ISO is set to 500 and AUTO? My 1Dx has a setting for AUTO but anything else must be a number alone. i.e. I cannot set AUTO ISO 500, only ISO 500 or ISO AUTO. For some reason you disagree with Canon but they know their cameras. Chances are they will gladly accept your payment and tell you something you don't want to hear. Why bother?

photoman43

I shoot with Nikon cameras, D500, D850 and a Z9. I use Auto ISO on all three along with Matrix metering. In both Aperture Priority and Manual, assuming I make no change in aperture or shutter speed, the ISO will change as the light changes and/or as the composition changes. Matrix metering reads the light across the whole image and changes the exposure.

A slight change in composition can result in a different exposure. The changes are usually minor that I do not notice them in the image unless I look at the exposure data. If backgrounds change like from a solid blue sky to darker green trees, the exposure will change. I rarely use spot or center weighted metering as I prefer the way Matrix metering will adjust the exposure as certain conditions change. I sometimes use highlight weighted metering, but I am still learning how best to use (and not to use) it.

delder Loc: Maryland

My 2 cents.
Nikon D3100 experience
[legacy DSLR]
I long ago stopped using the SPOT metering for the reasons apparent in your Balarena Shots.
In the FILM days, we used to BRACKET our shots.
[24 or 36 (50 loaded) shots] .
Now that "Digital Film" is essentially free & unlimited, there is NOTHING wrong with retaining this practice. We ALSO have the benefit of IMMEDIATE review of the results, so we can learn what setting works best.

tillmanb

I appreciate everyone sharing their wisdom regarding my two photographs. What I have gleaned from your comments is as follows: The difference in the two photos appears to have been operator error. In one photo, the exact center of the scene was the ballerina in front. In the other photo, the exact center was a dark area near the rear of the room. The spot metering made precise pointing of the camera essential for consistent, proper exposure. The ec=-2 setting was also an error. Thank you all for helping me see this clearly.

tillmanb

The ISO speed is determined by the camera in the Auto ISO setting. The 500 figure was actually a different photo and DPP4 reported it. I shouldn't have included it.

One photo was actually:
ISO Speed 2500
Auto ISO Speed ON

The other photo was actually:
ISO Speed 800
Auto ISO Speed ON

IMHO I was wrong about the camera and Canon, and you all were correct. The camera is OK.

CHG_CANON Loc: the Windy City

Open the RAW in DPP4 and confirm the AF location, and if the EXIF indicates the metering link. You can check the camera too for the linked setting. This will confirm where the camera chose to meter.

wdross Loc: Castle Rock, Colorado

With my OM E-M1 mkIII and a narrow spot, that seems normal to me. I know that it is not a Canon, but it seems to be very similar in metering (ISO). This is why I widen my "spot" so the metering doesn’t swing as much. With the metering covering the full frame, the metering hardly swings at all unless there are very large areas of dark and light that come and go in the changing view.