Low light sensitivity

[Peter Rush]

I haven't had time to test this, but is the sensitivity of the sensor in low light reduced when switching from full frame to APS-C mode? I sometimes put it in APS-C mode for a further reach but wonder If I am sacrificing some low light capability in doing this.

Pete

[Dave Allen]

When I asked Sony tech people directly at a Sony A7rII training and sales even, they said that when in Super 35mm mode, the camera uses the full sensor, and they specifically stated when filming in low light, there is no low light advantage to shooting in FF mode.

[David Heath]

Originally Posted by Dave Allen

When I asked Sony tech people directly at a Sony A7rII training and sales even, they said that when in Super 35mm mode, the camera uses the full sensor, .........

I simply don't see how those statements can be reconciled. If the whole sensor is FF, then how can just using a s35 crop from it's sensor count as using the whole sensor?

Originally Posted by Dave Allen

.......and they specifically stated when filming in low light, there is no low light advantage to shooting in FF mode.

Again, this is not what would normally be the case. With all else equal, a bigger sensor will have a higher basic ISO rating than a smaller one - it's capable of capturing light over a bigger area. (Note this ONLY translates into better low light performance if we talk about the same f stop in each case. For that, the equivalent lens for the bigger sensor will have a bigger diameter and at the end it's that that really makes the difference.)

And the above is generally true if talking about physically differing sizes of sensor, or crops of a larger one.

If the sensor is oversampling, think of it like this. A number of photosites are being combined to give a single pixel output - but so are their noise outputs. The more used, the greater the noise averaging, so the better the S/N ratio. Use half the chip area, and you cut the number available by half - less averaging, so worse S/N. If we're talking about a fixed photosite count, then each must be larger on the bigger chip tha on the smaller - result less noise (so better base ISO rating) on the bigger chip.

The only time this wouldn't in general be true is if the resolution changed, so if taking stills, the resolution was the same as the no of effective photosites. So crop the sensor, lower the resolution. But for video - say 1920x1080 in each case - then crop the sensor and expect the performance in low light to drop for the reasons above.

[Paul Anderegg]

From my limited experience, the low light sensitivity is the same. If you set zebras to 100%, then switch to crop (APS-C), those zebras will be in the same places. APS-C mode is the same as 1.5X on the digital zoom scale when in full frame.

What you WILL have to deal with is INCREAED GRAIN and NOISE when shooting high ISO in APS-C mode. The higher the ISO, the more apparent the difference will be. A Speedbooster might level that playing field a bit.

Paul

[Simon Denny]

I haven't noticed anything different in FF v Crop. All looks good to me.