Sony A7SIII for underwater video - a list of Sony quirks to look out for

Hello all,

I recently switched from my trusted Lumix LX10 compact to a Sony A7SIII (ILCE-7SM3) for underwater video.

As expected, it’s a great upgrade, with features I was longing for (4K60fps, 10-bit colour, HDMI monitor connection capabilities, more battery life, workable AF…)

The choice of this camera was highly motivated by a great deal on an unused Nauticam NA-A1 housing, as well as the new 100mm macro and the MFO3 coming out in a relatively short time frame.

Very happy with the camera.

However, I came across some very specific Sony quirks affecting UW imaging, especially video, that I would have liked to know about before building the rig.

To help others, I’ll share them here for reference.

I think most apply to the FX3 / FX30 and some other Alpha bodies as well, and might be worth looking into for the new models like FX5, for instance.

1. NO TRACKING AF FOR UNDERWATER VIDEO (!!!)

This is the biggest letdown. While more recent Sony models like the a6700 do not have this issue, underwater shooters using the camera in a housing cannot use tracking AF.

Reason is simple: for video, tracking AF can only be activated with the touchscreen. Touchscreen which we can't use in a housing (cue in sad trombone....).
Yes, there is no option to map a button to a tracking AF on/off toggle in video mode (i.e. presse a button to lock on / start tracking what is in the square, something which is possible on newer bodies like the a6700).

The most frustrating part about this is that button-assignable tracking on/off toggle is available… in STILLS MODE.

But honestly, who shoots stills on a video-centric camera like the A7SIII or FX3?

Sure, standard AF, manual + back-button focus works quite well. But tracking AF would really help in some scenarios, like shooting small translucent subjects moving fast on both axes...
Sounds familiar? Yes, it’s blackwater video I’m talking about. For this kind of application, not having access to locking tracking on a subject is a major letdown.

And on the subject of tracking, note that ANIMAL EYE AF is NOT available in video mode. Yes, it can be selected in the menus, but Sony explains specifically that this is active in stills mode only.
This is a generational issue, and doesn't seem to apply to more recent bodies - unfortunately it was barely discussed online, and never addressed in a firmware upgrade, up to current 5.01

Frustrating as hell. Why simply kill tracking AF for underwater video shooters by having the camera tracking only rely on touch screen settings. I'm sure this a limitation for some land applications as well.

2. NO MANUAL WHITE BALANCE IN MEMORY PRESETS

The A7SIII does a good job at manual white balance underwater, as demonstrated in James Emery's tests here, for instance.

The camera offers 3 physical memory presets accessible by turning the dial to 1/2/3.

HOWEVER, when in these presets, setting a manual white balance is not accessible. You are locked out. No-can-do-because-memory-preset-mode message - Sure, you can switch to whatever Kelvin or WB preset you want, but you cannot manually set the white balance... Why, Sony? Just why?

To manually white balance, you need to be in standard manual movie mode (there is only one), which gives you access to 3 white balance banks where you can manually set / store white balance.

Practically, this means that you cannot combine your customised presets with manual white balancing underwater.
Say you have a 4K60fps preset, and a 4K120fps preset, then the 3rd one in S-LOG3, well, nope, no manual white balance. You need to be in standard movie mode, and switch your frame rate, picture profile, etc. from the main menus.

There is an option to recall memory presets, but nope, it can only be used… in memory preset mode 1/2/3... Argh

As a side note on memory presets, you cannot assign specific button customisation for each preset, as the button customisations are global.
So say you have a preset for artificial lighting where your WB balance is set, and another one where you would need to access WB more often, you can’t map a specific button layout for each mode.
The presets don’t record/store custom button layout options.

Lastly, note that manual WB info (like say 4900K M+6) is displayed in camera when set, but not accessible in post. You cannot find this info in the exif data which will just indicate "custom white balance", but not what it was set to. Frustrating for tests, if setting the WB manually multiple times at different depth. You would need to record the data on a slate to access it after shooting...

3. HDMI DISPLAY / OUTPUT ISSUES

I was super happy to finally get to connect a monitor to help my ageing eyes, see what I was shooting better, have better viewing-angle ergonomics, etc…

However, this didn’t come without a couple of surprises:

1. If mirroring the camera display, the camera outputs a square image, based on the camera monitor, so the mirrored monitor image is quite small on a 5” monitor, with lots of unused space - a little bigger than the camera screen, but not massively.

There is the option to output a clean HDMI feed (intended for in-monitor recording), which will use the whole monitor space and look great, but this comes at the cost of recording information - you do not even see if you are recording, and have to check the camera screen for that.

2. In mirroring mode, the A7SIII does NOT output data such as focus peaking or zebras. These are not sent over HDMI, unlike on other cameras like Panasonic and, I think, Canon.

This means you have to rely on your monitor for this. I use the Weefine WED-5 Pro monitor, which has acceptable peaking implementation, more or less matching the camera’s when set to level 7 (but just not as precise).

However, when it comes to zebras, the way Weefine has currently implemented zebras on the monitor is the reverse of what you would expect, and they are basically unusable as is.
This has been discussed with Weefine and we hope a firmware upgrade will fix this.

4. OVERHEATING AT 120fps WHEN SHOOTING IN A HOUSING

Heat management is good on the A7SIII. I ran some land tests at 4K60fps, continuous recording, AF-C on, with no overheating at 27°C.

Ran the same tests at 120fps: perfect, no overheating.

However, inside a housing in water over 27°C (common in tropical / subtropical locations), with a monitor connected, the camera overheats easily at 120fps, causing shutdowns. I haven’t measured precisely, but we’re in the under-5-minutes-of-4K120fps range… be careful if planning to shoot a lot at 120fps (blackwater video, anyone?). Yes, this is with the heat warning sensor set to high...

5. BATTERY LIFE: A WORD OF CAUTION

Lastly, battery life is workable, but be careful, especially with a monitor.

Just to give you an idea, internal battery life for 4K60fps recording on the A7SIII is actually 135 minutes of continuous recording according to Sony.

This is exactly the same on, the FX3, which uses the same NP-FZ100 battery pack (and has essentially the same video implementation as the A7SIII).

FX3/A7SIII: 135 min continuous / 95 min actual recording

In real life, my land tests on the A7SIII gave me 95 minutes of continuous recording at 4K60, so 30% lower than the continuous quoted figure, but matching Sony's 95 minutes actual recording figure perfectly.

But this is in ideal conditions, camera not in a housing, 27°C, no monitor connected, and while AF-C was on, it was on a still subject, and relatively newish battery.

And then in real-life UW shooting situations, in a housing with the monitor, with less than 5 minutes of actual shooting (!) at 120fps, the battery was drained to 23% remaining on a 90-minute blackwater dive.
This was for 5 minutes of shooting, with auto-off activated.

I’m currently looking into battery pack options for the housing's strobe trigger space, and have found one which works but has an auto shutoff feature which cannot be disabled.

I'll mention a last one: APS-C/Super 35 crop mode (super useful for macro) can only shoot 1080p video, not 4K - but this is offset by Sony's clear image zoom function, which allows you to crop in without much IQ loss due to digital upscaling (see here for more details)

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Anyway, these are the little Sony quirks and aspects to take into consideration when looking into Sony cameras for UW video. I'll flag any others that come up here.

Some of these, like tracking AF toggle and animal (even insect!) eye tracking for video, have been resolved on more recent bodies like the a6700, but others have not.
Definitely something to look into for underwater video, and that I certainly would have liked to know about.

Hope this helps.

Cheers and happy bubbles

Ben

Edited 1 hour ago1 hr by bghazzal