I took two pictures, both of them have equal exposure, I changed the shutter speed and aperture. One is brighter than the other. Is that normal? If not what do I do to make the two pictures look a like? Thank You.
ps. sorry what I meant is equal exposure and i changed both the shutter speed and aperture
If you're taking the identical picture under the same lighting, then any combination of shutter speed and aperture that gives the same total exposure should give the same results (reducing the light coming in by going to a smaller aperture (bigger f number) can be compensated for by keeping the shutter open longer).
With film, that starts to break down at long exposure times (multiple seconds) due to reciprocity failure, but digital sensors aren't affected by that.
Things that might cause problems:
If you're running in manual mode and setting exposure time and aperture yourself, the lighting may have changed between shots (clouds across the sun or whatever).
If you're running in aperture or shutter priority auto exposure mode, then if the framing of the shot is different, that may give a different exposure metering result (especially for spot metering, still possible for other modes).
If you're new to photography and have been using exposure compensation to change aperture/exposure time in auto exposure mode, or have exposure bracketing turned on, both of those are supposed to change the total exposure and thus brightness of the result.
Otherwise, it may be a lens or shutter fault. The lens aperture stays wide open while focusing with a DSLR, then closes to the set value just before taking the picture, then reopens. It's possible that there's a problem with that stop down mechanism - for example, the aperture blades may be a bit sticky and taking longer to close than they should, so the picture may be being taken while they're still closing, giving a brighter result. Shutter problems are also possible, though probably less common.
If everything else is the same except the shutter speed, of course one will look brigther than the other. That's perfectly normal and expected.
Aperture, shutter speed and ISO all control the final exposure. So if you want to take pictures with different shutter speeds, but you want same "brigthness", you need to adjust the aperture or ISO accordingly to compensate for the change in shutter speed.
You can compute a EV expsoure Value for each exposure:
iso 200 , 1/160s, f/36 = 16.6 EV
and iso 200.1/320s, f/22 = 16.3 EV (this is the brighter image)
To make them equal you should have used iso 200, 1/320s , f/25 = 16.6 EV
Compute Aperture 1 stop-up: 36 / sqrt(2) = 26/1.4142 = 25.5
Even if you did everything correct (e.g. you just use aperture priority mode and you used metering mode that uses a large area), the exposure will not be exactly the same because the camera is only going to adjust the exposure time in discrete steps. E.g. you can expose for, say, 1/60 seconds, but you cannot expose for, say, precisely 0.01835 seconds.
This can cause problems when doing certain image stacking tasks when e.g. the pixelwise median, maximum, or minimum of a set of images is needed. You then need to correct for the differences in exposure, this requires transforming the pictures to linear colorspace, measuring the brightnesses and then dividing the brighter picture by the factor needed to make this exactly as bright as the dimmer picture and then transforming the pictures back to sRGB.
