Why is ISO limited to 100 for exposures longer than 1.3 seconds on the Canon PowerShot SX60 HS?
Asked 5/7/2018
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On my Canon PowerShot SX60 HS, if I set a long shutter speed (longer than about 1.3 seconds), the camera will not let me choose ISO above 100. The manual confirms this behavior in Tv and M modes.
Why does Canon impose this limitation? Is it due to sensor noise, image quality, or some other technical reason? Is there any practical workaround without modifying the camera firmware?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
1
I think primary reason is that at high ISO and high exposure, noise makes images nearly unusable. Here is review of Canon's high ISO performance at long exposure. One of images is this:
As you can see, at same exposure of 15s, Canon 5d2 shows much more noise in ISO6400 shot. You camera sensor might accumulate too much noise during long exposure at high ISO to kill any image.
Camera manufacturers do that all the time, limiting performance in order to still produce useable images. Otherwise users will be upset:
Hey! I used 120 sec exposure at iso 6400 and all i got was bunch of noise. Your camera is garbage!
It's easier to limit camera's capabilities, rather than educate users about its limitations.
On the opposite end of spectrum you have modern DSLRs which can be set to ridiculous, nearly-useless ISO settings of 3.276.800. Probably, because Nikon wanted to brag about high ISO numbers to lay public, but actual Nikon D5 ($5000 camera) users understand that it's not real option.
Originally by user38691. Source · Licensed CC BY-SA 4.0
user38691
8y ago
0
Generated from our catalog & community — verify before relying on it.
This limit is most likely a manufacturer-imposed image-quality safeguard.
At long shutter speeds, the sensor builds up more noise, and using a higher ISO amplifies that noise even further. On a small-sensor camera like the SX60 HS, the results at long exposures and high ISO would likely be very noisy and often unusable. To avoid users getting extremely poor results, Canon appears to lock the camera to ISO 100 once the exposure exceeds about 1.3 seconds.
This kind of restriction is common: camera makers sometimes limit combinations of settings that would produce very low-quality images rather than allowing every possible combination.
Without using unofficial firmware such as CHDK, there generally isn’t a true way around the limit if the camera firmware enforces it. The practical workaround is to keep ISO at 100 for long exposures and compensate with a tripod, stabilization of the camera, and appropriate exposure settings. If you need cleaner night images at higher ISO or longer shutter speeds, a camera with a larger sensor will usually perform much better.
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