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What's the best way to make up for lost exposure when reducing flash power?
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<blockquote data-quote="WayneF" data-source="post: 497834" data-attributes="member: 12496"><p>There is a little more to it. I don't know your camera mode, so I will assume Auto, or A mode, or P mode.</p><p></p><p>In those modes. there is a Minimum Shutter Speed With Flash, most likely 1/60 second (some other camera models have a menu E2 to select it).</p><p></p><p>Do this very simple experiment, so you can see it happen, and will understand what is happening.</p><p></p><p>So in an indoor scene, with the flash turned off (internal flash door shut, which may not be possible if in Auto mode, maybe use camera A mode to see this),</p><p></p><p>then aim the camera at a similar indoor scene. Assuming Auto ISO, perhaps it is like ISO 3200, f/5.6, and 1/30 second shutter speed (this can obviously vary, you could tell us the numbers you see). My explanation depends on it being less than 1/60 second shutter speed, very often true indoors. P mode and very high ISO will be a wide open aperture, and might be a faster exception?</p><p></p><p>Then reach up and turn the flash on (open the internal flash door). The shutter speed will jump up to this Minimum shutter speed With Flash of 1/60 second, but the ISO 3200 and f/5.6 that it set will not change. It is not about exposure, 1/60 is faster than it was, which will underexpose the ambient. The idea is that you are now using flash, and don't need a very slow shutter speed (in camera A, P, or Auto modes).</p><p></p><p>This is an underexposure of the ambient light... 1/60 is too fast for the ambient. But no matter, because we are now using flash. However, you say you then are using Flash Compensation to reduce the flash output. </p><p></p><p>If the ambient exposure were sufficient, this may not matter, if the ambient exposure were acceptable. But since you need flash, probably it is not.</p><p></p><p>When the ambient exposure is near acceptable (very high ISO), the flash becomes just fill flash, and the ambient is considered the main light. But the 1/60 second (flash minimum) is limiting it, it will underexpose.</p><p></p><p>Indoors with flash, it is common to not use Auto ISO. For the reason just mentioned, and also because the incandescent ambient light is probably orange, making proper white balance be very difficult. In any formal portrait situation (with stronger flash), the goal will always be minimum ISO and a high aperture (like f/8) and the fastest possible sync shutter speed (1/200 second), to intentionally shut out all orange ambient, to keep white balance easy.</p><p></p><p>Indoors, it is more common to use much less ISO with flash (maybe ISO 400 as actually needed for the little internal flash, but not ISO 3200), which makes the ambient be very underexposed, including at the additional 1/60 second flash will impose. Maybe shutter speed was 1/4 second with the flash turned off, and so 1/60 with flash is less. But the flash takes care of it. And is not likely too much light if the ambient is insignificant.</p><p></p><p></p><p>But now we have to learn about flash. Note that flash exposure depends on distance. Flash maybe be correct exposure at the subject distance, but will overexpose closer things and underexpose farther things (inverse square law). So the first thing to learn to deal with is the inverse square law falloff.</p></blockquote><p></p>
[QUOTE="WayneF, post: 497834, member: 12496"] There is a little more to it. I don't know your camera mode, so I will assume Auto, or A mode, or P mode. In those modes. there is a Minimum Shutter Speed With Flash, most likely 1/60 second (some other camera models have a menu E2 to select it). Do this very simple experiment, so you can see it happen, and will understand what is happening. So in an indoor scene, with the flash turned off (internal flash door shut, which may not be possible if in Auto mode, maybe use camera A mode to see this), then aim the camera at a similar indoor scene. Assuming Auto ISO, perhaps it is like ISO 3200, f/5.6, and 1/30 second shutter speed (this can obviously vary, you could tell us the numbers you see). My explanation depends on it being less than 1/60 second shutter speed, very often true indoors. P mode and very high ISO will be a wide open aperture, and might be a faster exception? Then reach up and turn the flash on (open the internal flash door). The shutter speed will jump up to this Minimum shutter speed With Flash of 1/60 second, but the ISO 3200 and f/5.6 that it set will not change. It is not about exposure, 1/60 is faster than it was, which will underexpose the ambient. The idea is that you are now using flash, and don't need a very slow shutter speed (in camera A, P, or Auto modes). This is an underexposure of the ambient light... 1/60 is too fast for the ambient. But no matter, because we are now using flash. However, you say you then are using Flash Compensation to reduce the flash output. If the ambient exposure were sufficient, this may not matter, if the ambient exposure were acceptable. But since you need flash, probably it is not. When the ambient exposure is near acceptable (very high ISO), the flash becomes just fill flash, and the ambient is considered the main light. But the 1/60 second (flash minimum) is limiting it, it will underexpose. Indoors with flash, it is common to not use Auto ISO. For the reason just mentioned, and also because the incandescent ambient light is probably orange, making proper white balance be very difficult. In any formal portrait situation (with stronger flash), the goal will always be minimum ISO and a high aperture (like f/8) and the fastest possible sync shutter speed (1/200 second), to intentionally shut out all orange ambient, to keep white balance easy. Indoors, it is more common to use much less ISO with flash (maybe ISO 400 as actually needed for the little internal flash, but not ISO 3200), which makes the ambient be very underexposed, including at the additional 1/60 second flash will impose. Maybe shutter speed was 1/4 second with the flash turned off, and so 1/60 with flash is less. But the flash takes care of it. And is not likely too much light if the ambient is insignificant. But now we have to learn about flash. Note that flash exposure depends on distance. Flash maybe be correct exposure at the subject distance, but will overexpose closer things and underexpose farther things (inverse square law). So the first thing to learn to deal with is the inverse square law falloff. [/QUOTE]
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What's the best way to make up for lost exposure when reducing flash power?
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