I am shooting in natural light, with my subject facing a full floor-to-ceiling south facing window. You would think my meter would allow ISO between 200-400 in bright light, but I was lucky to get it to 640, with f/3.2 and 1/60 (manual mode).

I've read other places that people say put your ISO down to 100 for indoor shots for greatest clarity (especially sharp eyes) — but don't know how I can with subjects potentially moving. Is there a setting in my camera (Canon 5D Mark III) I am missing, or something that might be making my meter need more light?

  • 7
    \$\begingroup\$ "You would think my meter would allow..." Why would you think that? The most likely explanation is that the meter is correct, and your assumptions are wrong. \$\endgroup\$
    – Philip Kendall
    Mar 16, 2014 at 6:48
  • 2
    \$\begingroup\$ Are your images coming out with the correct exposure? That's how we can know if the meter is right or not. If your instinct about what should be required is right and the meter is off, the images you are getting will be overexposed. Is that the case? \$\endgroup\$
    – mattdm
    Mar 16, 2014 at 12:15
  • \$\begingroup\$ Thanks for the responses - as a beginner I am grateful for all the kind help I can get. I only said you would think I could get to ISO 400 because many books and sites I have been reading say 400-800 is possible for indoors (maybe I misread and that is for use with a flash). And as this is full unobstructed, floor to ceiling southern light I thought my camera would register it as almost outdoor light. \$\endgroup\$
    – LeylaMB
    Mar 17, 2014 at 3:29
  • \$\begingroup\$ When I follow the camera's meter and zero out (with a higher iso and keeping ss and f stop in a safe range) the exposure is correct, so yes, the camera is doing its job. BUt I was wondering that as the light is SO bright, I was wondering if there was a special camera setting that makes the camera less sensitive to light that I might have accidentally set up. I will try with a lens that has f1.4, but I was hoping to avoid such a narrow focal plane. Any other suggestions would be very welcome (I am trying to do without flash) - thanks in advance. \$\endgroup\$
    – LeylaMB
    Mar 17, 2014 at 3:30
  • \$\begingroup\$ If your subject is in the direct light of the window but the rest of the room is darker you will need to change the metering point of you camera so it meter only on the subject (or move closer to the subject so it fills the viewfinder and meter it ) otherwise the meter may be reading the darker room. You may still need an higher ISO if the direct light is not sufficient for lower ISO. \$\endgroup\$
    – Alaska Man
    Oct 23, 2018 at 18:15

3 Answers 3


It would take a rather brightly lit room to get your ISO down that low. I've got a low hanging, 5 light fixture in a small white room and I just metered f/3.2, 1/60 and ISO 1250. So, bright sun is definitely going to help, but ISO 200 or 100 inside, at f/3.2, without flash is an impossible dream.

You either need a faster lens (like a f/1.4) - but that is going to require some razor thin depth of field probably by setting it really low. Or you need a flash. If you haven't used a 'real' flash before - they have a bad rep till you get to know how to use them either bounce-style or off camera.

If you really want to shoot that low ISO inside, get a flash. Its well worth the investment.

But frankly, a Canon Mark III shooting at ISO 640 is completely fine. The noise really should be fine for a Full Frame camera at 640. Of the things to worry about, I wouldn't cry too much about it.

  • 2
    \$\begingroup\$ Indeed. ISO 640 (or, for that matter, ISO 1600) is just another setting on a modern DSLR. Only pixel peepers would notice any difference, and a nudge of the luminance noise slider in any raw converter will eliminate even that. \$\endgroup\$
    – user2719
    Mar 16, 2014 at 5:48
  • \$\begingroup\$ I was going to say, I routinely shoot at ISO 6400 without issue on my 5D Mark iii if that is what you are actually talking about. \$\endgroup\$
    – AJ Henderson
    Mar 16, 2014 at 5:55
  • 1
    \$\begingroup\$ photo.stackexchange.com/a/43758/17441 for reference on Canon ISO settings. \$\endgroup\$ Mar 16, 2014 at 5:55

Why is my camera metering indoor scenes as darker than I expect it would?

Because the scene is darker than you assumed it would be. Indirect sunlight is not as bright as direct sunlight. It is usually nowhere near as bright. Much, if not all, of the light that is shining through the window has likely already been reflected by something else and unlike when you are outdoors, you're not getting any reflected light from directions other than the direction the window faces. Think of the window like an aperture. It is restricting the light entering the room to one direction. While it is allowing light from the south at specific angles to enter the room it is also not allowing light from above, below, east, north, or west to enter the room.

You would think my meter would allow ISO between 200-400 in bright light, but I was lucky to get it to 640, with f/3.2 and 1/60 (manual mode).

It is not the meter that isn't allowing you to shoot at the ISO, aperture, and shutter speed you would prefer, it is the amount of light that exists in the conditions under which you are shooting. The meter is only telling you how much light is present in the scene.

  • \$\begingroup\$ Understood - so even though it is direct sunlight, unobstructed and not reflected- the fact that it is not the same and lacks the multi-directions of outdoor. \$\endgroup\$
    – LeylaMB
    Mar 17, 2014 at 3:32

The short answer: It's darker then you think it is. Here's a depiction of various brightnesses and an exposure value which nominally will give correct exposure at that brightness. Note that these are overlaid — the area of the whole circle is what matters, not the separated rings.

exposure value as circles — this chart by Matthew Miller, CC-BY-SA 3.0

This seems shocking, because our eyes are so good at adjusting, but a scene in sunlight is 500× brighter than a typical home interior.

Your settings of "f/5.0, shutter 1/160th, ISO 6400" correspond to a correctly-exposed image at EV 6 — exactly what's labeled as "home interior" on this chart — so theory is meeting reality.

EV 0 corresponds to a one second exposure at a theoretical f/1 and ISO 100. You can calculate in stops from there by hand, or use a site with an EV calculator.

Note that higher ISO isn't, itself, what's causing the noise. That's really caused by lack of light, and, short of getting more light in, it's actually not a bad thing. See this answer for more detail and practical examples.

If you want a lower ISO, you'll need either slower shutter speed, wider aperture, or more light. If you want to go down to ISO 800, you'll need three stops to compensate (because you halve 6400 three times to get to 800). That means you could get equivalent exposure from f/5.0, ISO 800, and 1/20th of a second. You'll probably need a tripod, or good image stabilization, to get acceptable results, though — and if you're shooting people, they'll have to be very still. Opening your aperture all the way to f/4.0 gives you another ⅔ stop — but that only gets you to f/4.0, ISO 800, and 1/30th.

My suggestion is to invest in a low-cost off-camera flash, either optically triggered or as a radio slave.

  • \$\begingroup\$ Nice answer, but don't forget the CTO filter on the flash. If you think changing the white balance on your camera is worth the trouble, you should do it for your flash too. \$\endgroup\$
    – Orbit
    Dec 23, 2017 at 12:25
  • \$\begingroup\$ @Orbit In my experience, in most homes, shooting with bounced flash easily provides the primary light source and there aren't mixed color-temperature issues unless there happens to be a long hallway leading to another room with lights on in the distance or something like that. CTO gels are a nice tool but not a requirement in many cases. \$\endgroup\$
    – mattdm
    Oct 6, 2019 at 15:31
  • \$\begingroup\$ You are right, the question states in natural light, so unless it is close to sunset you wouldn't need a filter. Still think that having filters is just as important as being able to change the white balance of your pictures, and that that is often forgotten. \$\endgroup\$
    – Orbit
    Oct 20, 2019 at 8:43

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