This is one in a series of posts on the Sony a7RIII. You should be able to find all the posts about that camera in the Category List on the right sidebar, below the Articles widget. There’s a drop-down menu there that you can use to get to all the posts in this series; just look for “a7RIII”. If you’re new to this thread, it’s a good idea to start reading here.
The last post proposed a strategy for managing ISO settings and exposure on the a7RIII when setting the exposure manually. I think this is an excellent way to do things with a camera whose read noise relates to the ISO setting. But it’s quite different from the way most folks use their cameras. Now I’ll write about a way that should be a bit more familiar that gets most (but not all) of the same benefits and the purely manual approach.
The cardinal rule remains the same: If you can, expose to the right (ETTR) at base ISO. With the a7RIV, you can use the live view histogram, or take shot and look at the histogram as you review the capture. Set your exposure compensation (EC) so that your meter will give you that exposure. You might want to bias the exposure slightly towards underexposure if the light is changing since it’s easier to deal with a bit more noise in the shadows than blown highlights.
But let’s ask what you should so if the ETTR exposure is too long for you or requires a wider lens opening than you want to use. If the lens opening is the most important thing to you:
- Set the ISO to base ISO
- Set the camera to aperture-priority exposure mode
- Set the aperture to whatever you wish
- If the ETTR exposure is acceptable, you’re done; take the shot
- If the shutter speed is too long, and you want some extra highlight protection, crank the EC down (make the numbers more negative) until you get an acceptable shutter speed.
- Stop when you get to two stops underexposed from the ETTR setting.
- If that gets you an acceptable shutter speed, you’re done; take the shot.
- If not, set the ISO to 640
- If the exposure is acceptable, you’re done; take the shot.
- If the shutter speed is too long, and you want some extra highlight protection, crank the EC down (make the numbers more negative) until you get an acceptable shutter speed.
- Stop when you get to three stops underexposed.
- If that’s still a short enough exposure, increase ISO until you get a shutter speed you can live with, keeping the EC three stops underexposed.
Sounds like a lot of fiddling, but after you’ve painstakingly followed the steps above a few times, you’ll get a feel for it and will be able to take many shortcuts. The idea is to make use of the highlight protection that comes with what would generally be called underexposure, and boost the gain in postproduction, which, thanks to the nature of the a7RIII sensor, has practically no noise penalty.
If the shutter speed is what’s key for you, use the above procedure, but set the camera to S mode and swap aperture and shutter speed in the protocol.
You will be fiddling with the EC dial in the a7RIII a lot if you use this procedure. Fortunately, Sony has put a dedicated EC knob right on top of the camera.
Den says
Quite new to your blog but love the insight. Great reading.
So in the most simple terms, are you saying you only ever need to use ISO 100 or ISO 640 when working with RAW? – assuming shutter speed and aperture are acceptable for the shot (as in 3 stop range).
Let say you’re shooting a bride and groom dancing by candle lights. My balanced exposure hits F1.4 / 250 / ISO 20,000. Would there still be an advantage taking this back to 640 (5 stop) or 3200 (3 stop). Or are you saying if you cant get back to 640 within 3 stops the DR benefit is not worth bothering with due to noise.?
Can I also ask a separate/optional question if you have a view, but in video SLOG2 on this camera, why ISO 800 as minimum rather than ISO 640? (A7RIII).
JimK says
I’m sorry; I don’t know anything about video.
JimK says
That’s the gist of it.
If saying if you can’t get back to ISO 640 within three stops the dark viewfinder and possibility of a twist in postproduction aren’t worth it. I have been known to go to five stops in really contrasty situations, though.
Nick Ward says
Hi Jim,
Firstly, let me start by saying thanks for sharing your time knowledge and creating this valuable resource.
In the interests of making the ISO 640 and above as automatic as possible can we not also incorporate AUTO ISO? Unless I am missing something, we could set the AUTO ISOs MIN ISO to 640 and the min shutter speed to what ever is needed to freeze motion/avoid shake. The setting of the ISO will then be automatic using as little ISO gain as possible to achieve the min shutter speed and the Exposure Compensation is used to push the exposure as far right as possible (until see +109 zebras). E.g. In manual with 1/125 and f4 and -3 EC selected I can manually push the ISO a step at a time to 4000 before I see the zebra. Alternative I can set the Auto ISO with MIN ISO 640 and min shutter 1/125 and just push up the EC to just before the Zebra appears and the camera calculates ISO 4000 for me.
Please be kind if I made a schoolboy error and failed to follow your logic
Thanks
Nick
JimK says
If you do that, you won’t get the extra headroom that you could get by intentionally “underexposing”.