Barry Goyette
lvl.4
Flight distance : 14928 ft
United States
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Conrad Jay Posted at 2017-4-14 10:43
Interesting. Thanks for the info!
Yeah... sorta knew about the 500 iso lock... but the DR is degraded at this point... no? It says right on the website... If its locked into 500iso, then the dynamic range would only be about 10 to 11 stops rather than the full 12.8stops... Thats my biggest concern... Again, that simply base on the info from there website... Higher the iso, worse the DR.
yeah..no. Not quite how it works. Native ISO is the "true" ISO of the camera based on where middle grey falls (this isn't an exact thing, and manufacturers play around with "where" 18% grey falls.)
BASE ISO in a camera that shoots LOG is generally 2 or more stops faster than native ISO, and is set by the manufacturer as a compromise between dynamic range and noise. All sensors have a saturation point...a maximum highlight value that cannot be exceeded, but the number of stops that exist below middle grey, in the shadows, is much more squishy, and is usually "set" by the manufacturer based on a certain standard for noise (this is why there can often be a bit of controversy as to the actual DR of a camera). When you look at a xyla chart, you will often see several steps below what the stated shadow "range" is, but those steps are too noisy to be useful.
By setting the ISO at 500, DJI is essentially asking you to give the camera less exposure than it's native ISO of 100, which means it will accept a greater range in the highlights, and at the same time show an acceptable level of noise in the shadows, and this is the point where the sensor achieves "maximum" dynamic range. (it achieves this by applying some gain to the image, and that gain is what's truly responsible for extending the DR. At ISO 100, no gain is applied and thus the DR is less.) Rating the sensor any higher will simply push the shadows down deeper into the noise and not increase DR in a meaningful way. All true logs work this way, and you'll find that Arri, Canon, Sony and probably RED, all have a Base ISO that is several stops faster than their true, native ISO, for use in log gammas.
DJI isn't doing anything novel here other than "locking" the ISO (sony does this too, but offers some workarounds). Canon allows you to adjust ISO, but clamps the highlights for ISOs below base, effectively lowering the possible dynamic range. Arri does something similar. |
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