Puzzling D80 Auto-ISO behavior

<p>Ok, here’s a puzzling D80 behavior. I have Auto-ISO enabled with Max ISO set to 800 and Min shutter speed set to 1/100s. Now when I shoot in A-mode and set the aperture f/1.8 (it’s the 35mm G lens) with flash (SB600 pointing up), I get shots with ISO 100 and 1/60s shutter speed. Considering that I have set 1/100 as my min-speed, I’d have thought the camera would choose 1/100 and up the ISO to 180 (or so). In fact if I turn flash off it will keep the shutter speed at 1/100 and increase the ISO until it hits 800 and only then will it use slower shutter speeds. Anyone knows why using flash makes it prioritize on lower ISO over faster shutter speed?</p>

<p>Thanks.</p>

<p>My theory is that this is a Nikon software bug. And my present workaround is to shoot in M-mode. But I'd much rather shoot in A-mode if I can find a way to fix this.</p>

<p>you probably have the flash sync speed set at 1/60s which is the default. I think it can be set to 1/200 (check the manual).</p>

<p>Ah, that was it. My flash shutter speed is set to the max (1/60s). I thought the D80 could do 1/200s. But the menu options only show up to 1/60s. (Menu# 24).</p>

<p>Ok, that setting is for the slowest sync speed. Which is alright. So technically this should not affect the shots.</p>

<p>Ok, it seems it's by design. In A-mode you cannot get it faster than 1/60s. To get up to 1/200s you need to use S-mode. I can't think of any good reason why they would enforce such a rule. Oh well.</p>

<p>Nish, out of curiousity, set the flash to rear curtain/slow sync and see if that helps. You could also try shooting manual.</p>

<p>Thanks Jay, yeah, shooting manual seems to be the way out.</p>

<p>What is the use of auto-iso and flash?????????????</p>

<p>Hans,</p>

<p>The flash is bounced off a high ceiling and the auto ISO helps with getting a correct exposure for the background.</p>

<p>Weird. Flash sync speed was my first thought as well, but when I looked it up and saw it was 1/200s I decided I was on to nothing, and kept my mouth shut. Just as a thought, have you tried setting the flash to slow sync? It might be that the bit of firmware that limits the exposure to 1/60s is interfering with your auto-ISO settings. It sounds like a bug, but this might bypass the code that's causing the problem (with my software engineer's hat on).</p>

<p>To get the 1/200 sync speed you have to be in S or M mode. It makes sense when you think about it. Aperture priority mode is used to set aperture over shutter speed. When you start pushing shutter speed up to 1/200 while setting aperture you're getting close to manual setting mode anyway.</p>

<p>Thanks Paul, and yes what you say is true. What I really would have liked is something between A and M modes.</p>

<p>Hey Andrew. The firmware is set to use a max shutter speed of 1/60s in A-mode. Apparently, this is by design. I still don't think it's a good idea but then I guess the Nikon engineers had their reasons!</p>

<p>Nish - with flash mode set to slow sync as well as normal mode? (This overrides whatever you've got in custom setting 24.) I see enough weird software behaviour (often caused by my own programming) that I'm inclined to think it's a bug unless someone gives a good reason for it. The shutter speed limit on non-slow-sync flash feels like the kind of code that could cause this behaviour accidentally. Or that could be a complete red herring.<br />

<br />

Paul - that makes absolutely no sense to me. I've spent years using auto-ISO in aperture priority to keep the shutter speed faster than 1/focal length, and that's quite often a lot faster than 1/60s. Admittely this hasn't been in flash mode, but I don't see why I should suddenly accept that the background is blurry just because the flash has illuminated the foreground. It doesn't feel like a deliberate feature to me. Unless Nikon just decided that all flash photos will be taken at the minimum ISO in auto ISO mode, but that really ought to be a manual mode option.</p>

<blockquote>

<p>In A-mode you cannot get it faster than 1/60s. To get up to 1/200s you need to use S-mode. I can't think of any good reason why they would enforce such a rule.... What I really would have liked is something between A and M modes.</p>

 

</blockquote>

<p>Maybe I am missing something in the conversation, but can certainly have a faster shutter speed using Aperture Priority, provided the scene has enough light to <em>use</em> a faster shutter speed. The reason the shutter doesn't drop below 1/60th is because there simply ins't enough light. When using flash, you can set it up so that it doesn't drop below this mark knowing that the flash is now illuminating your subject. The camera meter is going to meter the scene without flash. Period. That is going to give you your EV. If auto-ISO bumps you to 800, and you are using aperture priority, the only thing left to adjust is the shutter speed. If the EV calls for a shutter speed of 1/200th, that is what you will get. If the EV calls for a shutter speed of 1/10, that is what you will get, UNLESS you are using flash. In that case, the shutter won't go below 1/60th. This is to prevent blurring of your subject. If you don't like the way the camera is metering the scene, you could attempt to dial in exposure compensation, but with Nikon, this would be a two-step process: you would need negative compensation to get a faster shutter speed (assuming the normal EV called for 1/60th) and the positive flash exposure compensation on the flash to override the negative compensation on the camera (it is cumulative with Nikon). Or, better yet, if you don't like the camera metering EV settings, shoot manual. That is your in-between.</p>

<p> </p>

<p>Andrew, I did not get a chance to try slow sync. Will try that and get back here.</p>

<p>John, yes you are missing something :-)</p>

<p>Here's what I get: ISO 100, 1/60s, f/1.8</p>

<p>Here's what I want: ISO 180-200, 1/100s, f/1.8</p>

<p>I have auto ISO enabled (max ISO 800, min shutter speed 1/100s).</p>

<p>Right now, with flash enabled, and in A-mode, I can't get what I want. I need to use M-mode. I am yet to try Andrew's slow sync suggestion though.</p>

<blockquote>

<p>If auto-ISO bumps you to 800, and you are using aperture priority, the only thing left to adjust is the shutter speed.</p>

</blockquote>

<p>Well, ISO is still at 100, so there's no need to adjust shutter speed here. Since auto ISO is on, the camera should ideally bump the ISO until it hits the max ISO specified before it changes the shutter speed. It does that when flash is off.</p>

<p>Incidentally, I spent a long time shooting in aperture priority with auto-ISO keeping the shutter speed fast enough to stop camera shake, and finding the pain of changing the auto-ISO speed limit annoying. It was only when I realised that I usually had auto-ISO working and that I could get the same effect more easily by working in manual + auto-ISO, tweaking the shutter speed as I zoom, that I finally stopped complaining about how hard it was to tweak the settings. (Well, mostly stopped.)<br />

<br />

I mention this in case you're in the same situation - manual mode might be your friend anyway. It's not so useful if you're usually bumping off minimum ISO and actually want the shutter speed to increase automatically.</p>