Sony A7sii underexposes

[pilsburypie]

Hi - Just sold all my Canon gear and video camera to get a small 1 camera setup. Got the A7sii a couple of days ago after plenty of research and have been using and testing a fair bit. I have an issue that can be worked around, but it is a real inconvenience - underexposure.....

For stills the camera underexposes by 0.7 stop. Easy to bump up the exposure compensation dial and get a well exposed photo. Histogram is nicely right of middle with no white clipping

For video the camera underexposes by about 1.7 stops in all picture profiles. The histogram is way over to the left and it needs a real exposure compensation boost, sometimes up to 2 stops to get a bright well expose shot with a healthy looking histogram. This makes it a real faff to have to keep changing exposure compensation when switching from stills to video. I tend to use cine1 or cine2 as my grading experience is in its infancy and at the moment I'm content with just tweaking. Either way, this underexposure is across the board.

Who else feels their A7sii underexposes? The underexposed shot is noisy, but correctly exposed is much better. Mine at least is consistent, I just wish I could assign the correct exposure compensation to stills and movie modes permanently and be done with it.

Thoughts and advice appreciated.

[blafarm]

I have not seen that.

What mode are you shooting in?

Does it still happen in AUTO?

What lens / adapter are you using?

[Guest Ebrahim Saadawi]

There's no such thing as a camera that underexposes, unless you're relying on Auto (the camera's metering system)

In video shooting, it's so delicate to expose correctly as video is compressed therefore cannot be corrected as stills, you need dead-on correct exposure, and more so, in video you're shooting a continuous sequence so you can't have an involuntary exposure change. I am saying all this to clear out: Shoot in Manual Exposure mode.

Now onto how to expose that camera.

Generally, (but no entirely), the highest image quality is achieved when allowing the most amount of light to reach the sensor. But, of course there's an upper limit to how much light (exposure) the sensor can take before it clips the highlights to pure white and lose information at that bright part of the image.

So, the highest quality exposure is the absolute highest you can achieve without clipping the highlights. This way you get the absolute highest DR the camera offers in all modes, as you use all the highlight data before clipping and use the cleanest shadows the camera can see in that situation. You're getting more information from both ends and ending up with a lot more robust image to grade. This works in baked-in profiles and better in Log like flat profiles (Cine 2 and 4 and S-Log2 -if you  have the grading expertise to process ETTR S-LOG2 footage that is-)

The technique us termed ETTR, Exposure To The Right (of the histogram).

Of course you darken the image in post and get the exact exposure you want, along with cleaner shadows and much richer image than under exposing and pushing up, MUCH cleaner. You can make it as dark as you want in-post, easily. So unless you're delivering files straight from the camera, use this, if you're indeed delivering straight off the card, then you need to use a contrasty profile and normak middle exposure to get a decent viewable image regardless of how it could look better if you had time to ETTR + Grade.

I have made extensive tests on various cameras on exposure an ETTR is the best for the A7S is all modes, by a big margin.

For achieving perfect exposure easily, the a7s has three exposure aids, Histogram, Zebras, and exposure meter.

The easiest way to achieve ETTR with the a7s, is Zebras. You set the Zebras setting to 100+, then bring up exposure in-camera until you see zebra stripes appear. These stripes indicate that this part is clipped entirely, so you go back a notch. This way you get the highest exposure without clipping easy and fast.

You can use the Histogram. But I don't find it as easy or as good as zebras in ETTR. But if you do, then expose until the data is to right just before crossing the right column of clipping.

Disregard the meter completely.

Just try the Zebras (set it to 100+ first) method, take the footage to edit and see how it looks when graded down and corrected vs normally or underexposed so you'd make your own decision.

If you insist on using Auto Mode and dial by Exposure compensation, you can use the same technique with zebras and Up you exp. Com. To the point prior they appear. Just over expose a bit in general, but I still don't recommend Auto exposure at all (Apert/shut priority).

I made extensive testing on this ETTR and Exposure matter you can find here:http://www.eoshd.com/comments/topic/7922-ettr-the-ultimate-exposure-technique/

[pilsburypie]

Thanks both for the replies - Firstly I'm using just the Sony 35 f2.8. Got this as a stop gap until the new Sony 24-70 f2.8 is released. I'm so used to that zoom focal length I'm having withdrawal symptoms already. Yes, I suppose I am shooting in auto, I kind of see aperture priority as semi auto, however I do see that the camera is automatically doing the exposure for me.

ETTR is not new to me - I have known it for a while under another guise HAMSTTR (histogram and meter settings to the right) - either way same thing, bright as possible just before clipping occurs. I'm a big fan of it as my previous camera, a Canon 1Dsii, although an incredible image machine, suffered from poor iso performance so I had to squeeze as much out of it as possible.

The 100+ zebra is great. I was previously relying on the histogram - getting it right over to the right before clipping. However, looking back at some shots, they are indeed a bit too overexposed and do have some burned out areas. I suspect that the histogram is not totally accurate. I have had much better success with the 100+ zebra method and knocking exposure comp back a 1/3stop after stripes appear.

I have also used the manual exposure with good success. However, this works best for me when I have a few seconds "thinking time" for shots. Very often with my subject (family/kids) I'm very run and gun, switching from stills to video in a flash. The metering (set to multi) seems to be different from stills to video, about a stop. I can be shooting stills, change to video and have the shutter speed leap up from 1/100 to 1/200 when I hit record. The auto mode i.e. aperture priority works for me in this run and gun situation. Given the time I do agree fully manual wins. Same as auto focus - it has it's place, but you can come unstuck.

This tends to be why I have exposure comp at +0.3 for stills and +1.3 for video. That seems to be a safe middle ground. Just annoying I can't have that automatically set. It's an extra step to dial it in every time when I chop and change between modes.

Very often I do use files straight out of camera. I have graded (Resolve) when I have had time, but found for the time and effort I put in, getting it right in camera can be nearly as good. I'm no pro so this often does for me. Do you have a suggestion for a picture profile? I'm using PP6 - cine2 which has what I feel to be a more natural look but does lack a bit of punch. Not had time to mess with that profile's settings yet, but I would like to add a bit of contrast to it so it is as good as there SOOC.

Thanks for taking the time to post your info, much appreciated.