Pls show examples where increasing brightness in post better than increasing ISO.

Started Oct 1, 2013 | Discussions thread
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gollywop Veteran Member • Posts: 7,985
Re: Pls show examples where increasing brightness in post better than increasing ISO.

bobn2 wrote:

ultimitsu wrote:

bobn2 wrote:

So, mostly the metering is checking highlights. The easy technique is to set 2 1/2 or a bit more stops of EC and spot meter off the highlights (if your camera lets you use EC in M). On most camera there are a few ISO settings to be working with, and you know those pretty well anyway.

This sounds quite interesting, can you elaborate a bit on how it works? why 2.5 stops?

Your meter should be calibrated to centre when it gets 18% grey as the nominal exposure (10/ISO lux seconds). So, you need to miscalibrate it to regard 100% as nominal. According to ISO, the ratio of highlight to 18% is 78/10 = 7.8 = 2.96 stops (funny what these discussions can do - I see I miscalculated a long time ago, and have been giving my highlights a bit less than I could - dial in 3 stops). So, if the meter reads highlight and thinks it's 18% grey, it will give 3 stops less exposure than it should - so you correct that with EC, or recalibrating the meter (most will not let you recalibrate that far). In practice if you know how much headroom your camera has, you could dial in more than that.

(Just going back through my working, I realise where the extra half a stop came from, ISO leaves 1/2 stop for specular highlights over white - I must have taken it off somewhere along the line - 3 stops is better)

Actually Bob, the 2-1/2 stops may be a good bet much of the time. It really depends on how well the metering spot fits into the brightest highlights. If the spot is fully contained in the brightest highlights, then you can use 2-3/4 to 3 EV. But, if the spot only partially contains the brightest highlights (and some less than brightest), the lowered metering will result in settings that will overexpose the brightest parts. In this case a lower EC, like 2-1/2 or even 2 is desirable.

This can become a problem when the brightest parts of the scene are important but relatively small, as when sunlight is shining through tree leaves. Lots of potential for blowing, but no "brightest" area large enough to meter fully.

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