Damn Auto-ISO and speedlight

Blade Canyon

Senior Member
I shot a friend's birthday party the other night. The D850 was on a tripod in the "studio" for strobe-lit head and group shots. I used the D800 and a Nikon speedlight for pics around the house. There were a lot of fun shots taken that way, but I was disappointed with overall quality and sharpness. Turns out the Auto-ISO was on. I had set ISO to 400 (so as not to overtax the batteries), but did NOT notice that Auto was on. I did notice the sharpness was a bit reduced when checking the shots on the back of the camera, but I attributed that to the 28-300 lens I was using.

The camera was shooting at 2200 to 2500 ISO as its default with the speedlight! Bugs the hell out of me that I overlooked that fact. These photos would have been so much less grainy at 400.

Now I want a menu setup option that says "No Auto-ISO when using flash" so I don't make that mistake again.

Any ideas for how to permanently avoid this mistake in the future?
 

Blade Canyon

Senior Member
Why do you use Auto-ISO, to begin with? :)

In many outdoor active situations, I know I want the shutter speed to be at X (to capture action and avoid visible camera shake), and I know I want the aperture to be at least Y (for sufficient depth of field). So I put those in manually and leave the ISO on Auto. The shots come out very close to what I want.

My mistake was leaving the camera set to Auto-ISO. Next time I picked it up I had in new distance-contacts and could not read the settings very well.
 

hark

Administrator
Staff member
Super Mod
Contributor
I shoot in Manual Mode when using any types of lights. Then everything gets set manually.

I'm surprised that the body would be grainy at ISO 2200. I've used ISO 6400 on my D750 (no flash or lights) without grain being an issue. However, the exposure needs to be set correctly. If you wind up raising the exposure during post processing, that will introduce more noise. Nik DFine should be able to help alleviate a lot of the noise though.
 
In many outdoor active situations, I know I want the shutter speed to be at X (to capture action and avoid visible camera shake), and I know I want the aperture to be at least Y (for sufficient depth of field). So I put those in manually and leave the ISO on Auto. The shots come out very close to what I want.

My mistake was leaving the camera set to Auto-ISO. Next time I picked it up I had in new distance-contacts and could not read the settings very well.

That is exactly how I shoot birds. Auto ISO can be wonderful if used correctly. I rarely shoot flash so i will have to remember to check the Auto ISO setting.
 

LouCioccio

Senior Member
I shoot in Manual Mode (camera) set the Flash to TTL. Here is an image from a Blue and Gold Dinner. The cup cakes were exposed fine the flash fired but the one with the grand father but the flash DID NOT FIRE. I shoot RAW and was able to pull it back in. When I shot wedding ($$$) I shot in Manual Mode Camera so I had control but the Flash in most instances was in TTL. This will generally work. I came from Flash Bulbs to Electronic Flash and in the olden days you had to use a formula (algebraic) to find out what the aperture was supposed to be. If you have an EXIF viewer the cupcakes should give you:
Image Created: 2018:02:25 16:09:02
Exposure Time: 1/100 sec
F-Number: f/5.6
Exposure Program: Manual
ISO Speed Rating: 200
Exposure Bias: 0 EV
Metering Mode: Spot
Light Source: Unknown
Flash: Flash, Return Detected

But the grandfather and grandson will give you:
Image Created: 2018:02:25 17:12:01
Exposure Time: 1/100 sec
F-Number: f/5.6
Exposure Program: Manual
ISO Speed Rating: 200
Exposure Bias: 0 EV
Metering Mode: Spot
Light Source: Unknown
Flash: No Flash

. LDC_5580.jpg
LDC_5556.jpg


Lou Cioccio
 

WayneF

Senior Member
The camera was shooting at 2200 to 2500 ISO as its default with the speedlight! Bugs the hell out of me that I overlooked that fact. These photos would have been so much less grainy at 400.

Now I want a menu setup option that says "No Auto-ISO when using flash" so I don't make that mistake again.

FWIW, I agree with you. We need other menus too, one to prevent D-lens from frequently ruining TTL BL flash exposure, and another to force TTL (vs TTL BL) without having to set Spot metering (which likely messes up ambient). We have menus for some of the most mundane things, but are missing some of the important features of automatic flash control.

But was this D800 on the camera then, able to communicate with the camera? Because if a D800 recognized a flash was present, D800 ISO should have advanced only 2 EV, to 4x ISO (like 400 to 1600 ISO). If this 4x increase were from ISO 100 to ISO 400, that would be just about right for indoor bounce flash. But IMO, higher ISO only just means the flash level is always reduced to fill flash level, which might be great if planned that way, but not by surprise.

Nikon has gone through a few phases with Auto ISO and flash. The earlier Nikon DSLR models (D70, D80, D200, D40, etc) always did exactly what you want. Auto ISO would NEVER advance past minimum if a flash was detected present. That lasted until the D300S in 2009, when then ISO would always fully advance as determined by the ambient. Except even today, Auto ISO still will not advance if a manual flash is detected (manual flash cannot react to ISO changing).

Then after 2009 (D300S and later, for only a few models, like the D3000 and D5000), Nikon cameras went through a phase where Auto ISO was always determined by the ambient light level, and the flash had to work into any higher ISO that it might discover present, and it became fill level then. And any well-exposed indoor ambient is normally orange or green, different color than the flash. We had to turn Auto ISO off to use flash. I suspect this was an unfortunate push towards their "balanced flash solves all" concept, but Auto ISO does not work well with flash. We can of course always turn Auto ISO off.

And it was bad, and it lasted only a short time, roughly a year, until changed again. Nikon Auto ISO with flash philosophy changed again in 2010, affecting from D7000, D5100, D3200 and following, including D800 in 2012. And now, if Auto ISO is on, ISO will advance at most only 2 EV (or to 4x ISO). Which was good if ISO 100 minimum and using bounce flash.

So now (including the D800), Auto ISO should advance at most only up to 4x ISO if a flash is detected present (if it can communicate with the camera). That 4x can still be quite high if the Minimum ISO was already set high.

If the D800 camera (and later models today) recognize that a manual flash is present, or if using the Commander, then Auto ISO would be ignored, and ISO would Not advance past the minimum setting. If no flash was recognized present, then Auto ISO is determined by the ambient level. And a recognized TTL flash might advance 2 EV, up to 4x Minimum ISO. But even at 4x, if the ISO goes high enough to make the indoor ambient seem normal lighting, then the TTL flash is metered as only fill level.
 
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Blade Canyon

Senior Member
FWIW, I agree with you. We need other menus too, one to prevent D-lens from frequently ruining TTL BL flash exposure, and another to force TTL (vs TTL BL) without having to set Spot metering (which likely messes up ambient). We have menus for some of the most mundane things, but are missing some of the important features of automatic flash control.

But was this D800 on the camera then, able to communicate with the camera? Because if a D800 recognized a flash was present, D800 ISO should have advanced only 2 EV, to 4x ISO (like 400 to 1600 ISO).

I remember you did a test on that, or asked other users to test it. I was surprised that my camera did NOT go past 2 EV when I tested it because I had a previous bad experience with Auto-ISO and flash, and it seemed like more than 2 EV. Yet when I tested it, it was 2 EV, just as you predicted. (I don't remember what body I was running back then.)

Now I get 2200 to 2500 with ISO set at 400?
 

WayneF

Senior Member
I remember you did a test on that, or asked other users to test it. I was surprised that my camera did NOT go past 2 EV when I tested it because I had a previous bad experience with Auto-ISO and flash, and it seemed like more than 2 EV. Yet when I tested it, it was 2 EV, just as you predicted. (I don't remember what body I was running back then.)

Now I get 2200 to 2500 with ISO set at 400?

ISO 2200 is a half stop setting. The Auto ISO does frequently do 1/6 stops though, and 3/6 is a half. So the half stop is not any puzzle, but higher than 2 EV is the puzzle, at least as I originally stated it. There is a little more though.

The way that you can repeat that 2200-2500 result (intentionally cause it again) is to set either or both your flash compensations, the one in the camera menu, and/or the flash compensation set directly on the SB-800 body, either or both set to bit of positive flash compensation. If One of them is set to + 1/3 EV, then your ISO 400 Minimum might see ISO 2200. If both are set to + 1/3 EV, you might see the total of ISO 2500 (which is + 2/3 EV total compensation). They add.

Apparently this "only 2 EV above Minimum ISO with TTL flash" notion is Not limited by requests for additional flash compensation, which does seem reasonable.

A quick way to check if all things are actually as you believe them to be is to check the Info button (or top LCD) to notice the +/- compensation icon. This result will also show in the Rear LCD results (on screen that shows ISO settings). The icon will be on if any of the three comp sources (Exp comp, flash comp on camera, flash comp on flash) are not zero, and if that's a surprise, then we ought to find out which is on. They all add to the final exposure.

Surprising (to me), adding Exposure compensation (in contrast with Flash Compensation) does Not increase Auto ISO more than 2 EV above minimum, but it does cause additional TTL flash that performs the requested compensation. Because Exposure Comp does affect both ambient and flash exposure goals.
Adding additional Flash compensation can increase Auto ISO more than 2 EV above minimum. I'm puzzled how that could be explained rationally. :)

The way it seems is that Auto ISO will Not expose the ambient reading more than the 2 EV (but then TTL will honor the Exposure Compensation anyway).

But as is the nature of flash, we do need to examine our result and decide if it needs retry with correction. :)
 
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Blade Canyon

Senior Member
D'oh! Because the camera was set to matrix metering, the flash changed itself automatically from TTL to TTL-BL (backlight). I bet that was the real culprit for the auto-ISO going so high. Off to do some more tests.
 
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WayneF

Senior Member
D'oh! Because the camera was set to matrix metering, the flash changed itself automatically from TTL to TTL-BL (backlight). I bet that was the real culprit. Off to do some more tests.

That was my complaint in my first here, there should be a menu to set flash metering mode in the camera (where the metering is done). Spot Metering is inappropriate for balanced flash, but it seems a terrible way to have to set pure TTL mode. A few older flashes had a switch on them to select TTL vs TTL BL directly, but those models are disappearing.

FWIW, the TTL BL is about BaLanced flash, not about the word Back Light. Search the D800 PDF manual for wod Backlight, and it is only found in regard to the illumination of the LCD displays. Hunt for word Balanced, and you find it several places about the flash, like page 185 :

i-TTL balanced fill-flash for digital SLR: Flash emits series of nearly invisible
preflashes (monitor preflashes) immediately before main flash.
Preflashes reflected from objects in all areas of frame are picked up by
RGB sensor with approximately 91K (91,000) pixels and are analyzed in
combination with range information from matrix metering system to
adjust flash output for natural balance between main subject and
ambient background lighting.


The next paragraph says:

Standard i-TTL flash for digital SLR: Flash output adjusted to bring lighting
in frame to standard level; brightness of background is not taken into
account.
Recommended for shots in which main subject is
emphasized at expense of background details, or when exposure
compensation is used. Standard i-TTL flash for digital SLR is activated
automatically when spot metering is selected.

That is of course TTL BL vs standard TTL. Nikon manuals tend to use the word Subject about the flash lighting, and the word background about the ambient, which is valid of course, and is the result of how things work, but the actual idea here is about balancing flash with ambient. Ambient has to be correct on the background, but ambient plus flash must be correct on the subject. Which means reduced fill flash.

The way things work is that any two lights added will be brighter than the brightest. The idea is that ambient metering meters ambient settings to give a 100% exposure result from ambient. TTL metering also meters flash to give a 100% exposure from flash. But two 100% exposures adds to 200% exposure of the subject, which result is one stop overexposed (if using TTL mode, we have to know to back off with manual negative flash compensation). There's a calculator for this at https://www.scantips.com/lights/flashbasics4a.html#percent . But what TTL BL mode does is to automatically reduce the flash level to only fill level (typically about -2 EV if in bright sun), to prevent most of the overexposure of two proper exposures added. 100% ambient with the TTL at -2 EV compensation results in only 1/3 EV overexposure of the subject, called Balanced flash. We could also add -1/3 EV Exposure compensation then (which reduces background too), however flash compensation is a bit erratic in TTL BL mode (because the automation continues to also do its thing).


My notion is that TTL vs TTL BL is not a factor about Auto ISO and the 2 EV limit. I was testing with a SB-800 which has the huge luxury of having a TTL vs TTL BL switch on the flash. The fact that flash compensation increases the 2 EV increase allowed was true of pure TTL mode.

However, very sorry, I just got very confused about it, because nothing I can do now will let my D800 advance ISO more than 2 EV above Minimum ISO (with flash). Now (from ISO 400), it holds at ISO 1600 regardless. Flash compensation no longer has any effect on it, yet it clearly did just a bit earlier. I cannot account for any change. It is not metering mode, nor TTL vs TTL BL mode, etc. But now I cannot repeat the previous test, and I have no clue why it changed on me. I still have the captured images that shows it was doing the ISO 2200 and 2500 before, but I cannot repeat it now?
 
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