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Forums Lobby MASTER YOUR TOOLS Nikon Speedlights & Lighting topic #59442
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Subject: "Why Shutter Exp mode does this?" Previous topic | Next topic
Beemer2 Silver Member  Scotland, UK  Nikonian since 07th Dec 2006 Sun 30-Sep-12 02:02 PM
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"Why Shutter Exp mode does this? "



Using D300s, 17-55mm and SB-800 iTTL no compensations set.

If I set my D300s to ISO200, manual mode, 1/60s shutter speed and F8 I get a good exposure.

If however I set shutter mode, 1/60s for the same subject the camera selects F2.8. The resulting image histogram is not much different to before.

Why would shutter mode use F2.8 rather than any smaller stop?

Ian

If only Mozart had had a camera

  

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blw Moderator Awarded for his high level of expertise in various areas   Richmond, US  Nikonian since 18th Jun 2004 Mon 01-Oct-12 02:04 AM
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#1. "RE: Why Shutter Exp mode does this? "
In response to Reply # 0



Remember that there are two meter readings in play. First there's the ambient. In your manual mode, you are set for 1/60, f/8. This is a significant underexposure, so if the flash doesn't go off, you get a very dark frame. I know that because in S mode, you set the same shutter speed and the ambient exposure is f/2.8 - three stops faster.

Why is the resulting histogram close to the same? Because the flash is being used to illuminate the subject, using TTL metering. The flash is working a LOT harder in the manual case, because without flash you're underexposing by three stops. (Or it could be more than that.) In both cases, the flash is providing illumination, but in the S case you're opened up three stops more, making the flash three stops closer to correct exposure.

If you repeat the experiment with a macro-distance subject, say a flower at 10" distance, you will find that the background is very, very different between f/2.8 and f/8.

_____
Brian... a bicoastal Nikonian and Team Member

My gallery is online. Comments and critique welcomed any time!

  

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Beemer2 Silver Member  Scotland, UK  Nikonian since 07th Dec 2006 Mon 01-Oct-12 04:07 PM
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#2. "RE: Why Shutter Exp mode does this? "
In response to Reply # 1



Brian,

I do recall reading Russ's good flash blog and your comment reminded me of it. Your point about background distance hit the nail on the head. I never have used Shutter mode with flash so this was a trial and I had not thought the process through.

thanks,

Ian

If only Mozart had had a camera

  

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Forums Lobby MASTER YOUR TOOLS Nikon Speedlights & Lighting topic #59442 Previous topic | Next topic