ISO Auto in Manual: overexposure

wev

wev

Senior Member
Contributor
I have been trying auto ISO (set to 800), as I have been shooting in sun/shade/sorta sun/sorta shade conditions lately. I have found very odd results and am loosing a lot of pictures. Here is an example from today. Very bright sun; Tamron 150-600 at 600mm, 1/125, f7.1 -- and the ISO pushes to the max 800, blowing out the image. This has only been resized and compressed for posting

DSC_1414.JPG


Is the camera simply trying to compensate for what it reads as contrast between the bird and background?

Another, full sun, 1/640, f7.1, and ISO maxed.

DSC_1359.JPG


Is this sort of thing to be expected using auto or is there something iffy about the sensor? I am about to sent the body in to have the shutter/mirror checked after some lock-ups, so I wanted to note this down too, if wonky.
 
Horoscope Fish

Horoscope Fish

Senior Member
I don't understand... Usually the idea of shooting in Manual with Auto-ISO enabled is to take control of the aperture and shutter speed and let the Auto-ISO function control ISO in order to maintain proper exposure. So why are you setting your Auto-ISO function to ISO800?
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Eyelight

Senior Member
Looks like the first shot was metering the darker body of the bird which does not look very lit. And the second shot metered the background. So, I don't know that either would necessarily be unexpected.
 
wev

wev

Senior Member
Contributor
Horoscope Fish said:
I don't understand... Usually the idea of shooting in Manual with Auto-ISO enabled is to take control of the aperture and shutter speed and let the Auto-ISO function control ISO in order to maintain proper exposure. So why are you setting your Auto-ISO function to ISO800?
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Click to expand...

Sorry -- set to 800 max auto iso. That is the only ISO control available in manual. If you try turning on the Anti ISO function otherwise, it say "Not Available."

Am I going about the controls all wrong? The manual is not at all helpful.
 
wev

wev

Senior Member
Contributor
Eyelight said:
Looks like the first shot was metering the darker body of the bird which does not look very lit. And the second shot metered the background. So, I don't know that either would necessarily be unexpected.
Click to expand...

I kinda thought that, which makes the auto useless as I can not predict or control what the hell it is going to do.
 
Horoscope Fish

Horoscope Fish

Senior Member
wev said:
Sorry -- set to 800 max auto iso. That is the only ISO control available in manual. If you try turning on the Anti ISO function otherwise, it say "Not Available."

Am I going about the controls all wrong? The manual is not at all helpful.
Click to expand...
On my D750, in the Auto-ISO menu, there are options for "ISO Sensitivity" (minimum ISO), "Maximum ISO" and "Minimum Shutter Speed". I set "ISO Sensitivity" to 100, "Maximum ISO" to 1600 (usually) and "Minimum Shutter Speed" to "Auto" but with the slider bumped one notch toward "Faster". Even though this last setting is irrelevant when shooting in Manual I use Auto-ISO in Aperture Priority mode as well. Anyway, back to Manual mode...

When shooting in Manual with Auto-ISO enabled (which is how I typically shoot) I choose my shutter speed and aperture and simply keep an eye on the ISO to keep everything where I want it.
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wev

wev

Senior Member
Contributor
Horoscope Fish said:
On my D750, in the Auto-ISO menu, there are options for "ISO Sensitivity" (minimum ISO), "Maximum ISO" and "Minimum Shutter Speed". I set "ISO Sensitivity" to 100, "Maximum ISO" to 1600 (usually) and "Minimum Shutter Speed" to "Auto" but with the slider bumped one notch toward "Faster". Even though this last setting is irrelevant when shooting in Manual I use Auto-ISO in Aperture Priority mode as well. Anyway, back to Manual mode...

When shooting in Manual with Auto-ISO enabled (which is how I typically shoot) I choose my shutter speed and aperture and simply keep an eye on the ISO to keep everything where I want it.
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Click to expand...

That is what I do, too. Here is the problem in the first picture -- it is Southern California, crystal clear, dry as a desert, full blazing sun bright out and I have reduced the speed all the way down to 1/125 shooting at 600mm and it still blasts the image into a gray scale and blown out whites. Go any lower in speed and the image is a blur and focus fails -- and it is still at 650 ISO. The image in the viewfinder looks great, of course, but I am lucky to salvage a picture out of photoshop.

To heck with it -- I am setting ISO at 100 and doing the thinking for myself from now on (which may not be an improvement, but I will know who to blame).

Thanks
 
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Paganman2

Senior Member
The Iso shouldn't really be a problem if its putting all the data to the right of the histogram, as 1000 + should not be a problem with pictures like these and esp, if there is no cropping.

P.
 
Horoscope Fish

Horoscope Fish

Senior Member
wev said:
That is what I do, too. Here is the problem in the first picture -- it is Southern California, crystal clear, dry as a desert, full blazing sun bright out and I have reduced the speed all the way down to 1/125 shooting at 600mm and it still blasts the image into a gray scale and blown out whites. Go any lower in speed and the image is a blur and focus fails -- and it is still at 650 ISO. The image in the viewfinder looks great, of course, but I am lucky to salvage a picture out of photoshop.

To heck with it -- I am setting ISO at 100 and doing the thinking for myself from now on (which may not be an improvement, but I will know who to blame).
Click to expand...
I guess I was just confused because your description of using Auto-ISO in Manual Mode wasn't matching mine. I'm also about as south as you can get and still be in California so I'm not sure what the issue is but, yeah... You gotta go with what works for you. Hope you get the issue sorted.
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wev

wev

Senior Member
Contributor
nickt said:
The exif says these shots were spot metered. Maybe that is the cause of the unexpected results.
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Ah, had not thought of that. I went to spot, as the clusters were so random on what was going to be in focus and with my shots there is little time to fiddle about. That said, I will try center and see if I see a difference.
 
D

Don Kuykendall_RIP

RIP :(
There is a difference in Spot metering and Spot focus. When I shoot BIF I have spot focus or 9 point focus and Center Weighted metering. I have rarely ever seen a good use for spot metering other than shooting the moon and it works great there.

For BIF I use
manual exposure set to 1/2000sec and F9
Auto focus set to spot
AUTO ISO min 100, max 3200
Metering mode to center weighted and depending on the brightness of the sky I may have the exposure compensation set to -1 to -2. I usually shoot a few and then look to see if I need to adjust.

I have been using this setup for a while now and if always works great and fast.
 
W

WayneF

Senior Member
nickt said:
The exif says these shots were spot metered. Maybe that is the cause of the unexpected results.
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Bravo, you are correct, right on, good detective work. If we look, the Exif does say Spot metering, and Spot requires beaucoup more experience and attention. Spot metering is absolutely worst choice for novices (they don't understand it). Spot will rarely be correct, or even ballpark, without considerable user attention and knowledge.

Not that it matters, but we could ask what spot? And then, didn't that spot come out about middle gray? That will true of any color or shade the spot was on. Was middle gray desired? For example, we just learn to know that if we Spot meter on a Caucasian face (to isolate it from the background), we dang well better compensate it about +1 EV (so the face won't be middle gray). But novices don't know things yet.

It was camera Manual mode and fixed ISO 800, so no form of metering could change the camera settings at all. The user set them.
So to even ask the question about what's wrong, we have to presume the user manually zeroed the camera meter to select those settings, and thought he was metering. But he better be very knowledgeable about Spot metering to expect a correct exposure. Spot metering ain't easy. :) Spot is a very advanced technique, requiring considerable experience and special knowledge. The spot chosen should come out middle gray, regardless what it is or was.

One exception: Spot metering is used indoors, using automatic TTL flash (which does NOT Spot meter itself - it has its own method), will switch flash from TTL BL to TTL mode, and the ambient (where we use flash) is way down, insignificant, well underexposed. So even if the camera is not fully Manual, the ambient is too far down for Spot (or any metering) to affect camera settings for it.


Simply try using Center Weighted or Matrix metering next time, and the camera metering should improve greatly. :) This was not the cameras fault. It is the users fault for not understanding Spot metering well enough to use it. Not so many of us do.
 
M

mikew_RIP

Senior Member
The D7100 has the tendency to over expose in auto ISO,i have -1/3 set in all the time,i use Matrix metering,after ignoring advice over and over again now i have used it a few times i like it more and more.
 
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Paganman2

Senior Member
mikew said:
The D7100 has the tendency to over expose in auto ISO,i have -1/3 set in all the time,i use Matrix metering,after ignoring advice over and over again now i have used it a few times i like it more and more.
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Isn't the over exposing a good thing, if it pushes all the data to the right and helps noise control aka ETTR?

P.
 
Horoscope Fish

Horoscope Fish

Senior Member
I don't find Spot metering particularly esoteric or advanced: It meters off a very specific area. Not so tough to understand. How Matrix metering works is far more complicated in my opinion.

As I've said before, the job of the camera's light meter is NOT to render perfect exposure. What correct exposure is for a particular shot is a subjective assessment to be made by the photographer. The objective data the light meter provides will expose properly for middle grey. Matrix, Center Weighted, Spot: They ALL do the same thing, expose for middle grey, all the time, every time (yes, I know, Matrix has a database of "scenes' that it uses, etc. etc.). Think of it as a "Middle Grey" meter because really, that's what it is. It's up to us, as the brain behind the camera, to use the known baseline of middle grey exposure provided by the light meter to adjust our exposure to what is "correct" for that particular shot.

That... And learn to read and understand histograms and/or watch your blinkies screen to prevent blowout.
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