GH4 Aperture Priority (with AutoISO and shutter speeds) - Panasonic Method?

TheTrickster

TheTrickster

Well-known member
I'm looking to further understand the use of Aperture Priority mode on the GH4 using AutoISO.

As I'm recording in changing environments (underwater), I ideally would like to fix Aperture (so my depth of field is static), I would like to fix the Shutter Speed (obviously) and so would like the camera to adjust the Gain/ISO to keep the exposure constant.

In Manual (Movie) mode you cannot set the ISO to AutoISO, so that mode is out, can't really use Shutter Priority as I need to keep the lens stopped down to around f6-f8 (as I presume it will try and set the Aperture wide open) - so my final thoughts on this are to use Aperture Priority and hope the camera is doing some voodoo to keep the shutter speed up...

From playing with the camera in Aperture Priority (Picture) mode - as movie mode doesn't show any details of shutter or iso :(
it does appear that it ups the ISO and keeps the shutter at 1/60 when moving to darker scenes and then in lighter scenes it increases shutter speed (when I presume its moved the ISO back to 200)

All this is guess work, as I have no idea if it definitely sacrifices ISO before shutter speed? I've read on Personal-View (from GH3 comments) that the minimum shutter speed is 1 / ( FL *2 ) the focal length but wondered if that is confirmed?

I wondered if anyone out there knew how Panasonic have programmed the GH4 for movie mode while in Aperture Priority.

Thanks!
 
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Well, I did a quick test and verified many of your findings. But I was able to get auto ISO working using video without being in the creative video mode. Unfortunately, when you do this your lose control over the picture style used.
 
Thanks for that, I had presumed that when using the REC button while in a Photo mode, if you had the camera set to AutoISO it reverts back to ISO200.

What mode where you in?

Why oh why can't they get the camera to display on screen what its doing while recording (ISO / Apeture / Shutter etc)...
 
When using WIFI and smartphone the GH4 shows all exposure values. You can study the camera logic with WIFI. Please Panasonic make those exp values visible in-camera too with FW fix. And auto iso with EV-control too...
 
I was in manual mode. I did another test, and it appears that no matter what your ISO is set to, it will use Auto ISO when recording non creative mode video. When I set the ISO to 200, and started recording with the REC button with the camera pointed toward darkness, the resulting video was in ISO 6400. I have no idea what the aperture and shutter speed or angle was since it's not shown on video review when doing non creative mode manual video.
 
Wow - thats interesting, that appears to be a bug in the firmware for that then, if you have specified the ISO...
 
estarkey7 said:
I was in manual mode. I did another test, and it appears that no matter what your ISO is set to, it will use Auto ISO when recording non creative mode video. When I set the ISO to 200, and started recording with the REC button with the camera pointed toward darkness, the resulting video was in ISO 6400. I have no idea what the aperture and shutter speed or angle was since it's not shown on video review when doing non creative mode manual video.
Click to expand...

If your mode dial is in A,S,P or M position the video exposure is always fully automatic and auto iso. Only creative video mode lets you use different exposure modes (via menus).
 
Ah okay, so that rules out using any of those modes then (as you have no control of Aperture to Shutter either then)
 
Selecting th "Photo 4K" option in the creative video modes gives you indirect access to your settings by looking at a saved frame capture: pause an in-camera playback clip, press the "select button", and then the "save frame" option, which saves the frame to SD card right after the video clip. In A-priority and auto-ISO, shutter speed and ISO will display with the saved frame. I just found that in low light the shutter speed will fall to 1/30 sec. before ISO goes up.

The only difference in the "Photo 4K" option I can see is the ability to shoot in 3:2, 4:3, or 1:1 formats as well as 16:9 - all having the same 8.3 MP frame size by increasing height while decreasing width. I've found this particularly useful in nature shooting, and in performances, when pulling 4K stills of players is the object.

Peter
 
Trickster,

There is a way to use APERTURE PRIORITY and AUTO ISO. With the dial on top set to the "movie camera" icon press the "Menu/Set" button to get the menus, select the top "camcorder" icon and on Page 1 select EXPOSURE MODE. Press Menu/Set or right cursor control, choices are P, A, S, or M (you know what those stand for). Select A and press Menu/Set. You are now in Aperture Priority exposure mode when you set the dial on top of the camera to "Motion Picture" (the movie camera icon).

Until you change it. I keep mine set to M as I work in Manual Exposure mode primarily, I knew P, A, and S were there on that menu, I just never really use those, but A with AUTO ISO should work for your situation and needs.

Now, if you exit the menus by a light touch on the shutter button, you can select either a specific ISO or AUTO. I think this is what you want. Give it a try.
 
Hi Bruce, thanks. Yes I know that AutoISO works with both Aperture and Shutter priority modes (within the creative movie mode) - my main issue, is understanding how the camera behaves in these circumstances... We don't know the weighing the camera gives to each of the options to provide adequate exposure...

Example: In Aperture Priority Mode, AutoISO, Aperture set to f8, a native 12mm lens. Scene is underexposed by 3 stops. The camera has 2 choices slow the shutter or increase the ISO. At the moment I can't say for sure which one it chooses first. It appears, that for underexposed scenes its using ISO and for overexposed scenes its using shutter.

If they would just add AutoISO to the Manual mode (within creative movie) then I would be very happy, as it will only fiddle with ISO - Plus add the upper limit option too! :)
 
TheTrickster said:
Example: In Aperture Priority Mode, AutoISO, Aperture set to f8, a native 12mm lens. Scene is underexposed by 3 stops. The camera has 2 choices slow the shutter or increase the ISO. At the moment I can't say for sure which one it chooses first. It appears, that for underexposed scenes its using ISO and for overexposed scenes its using shutter.
Click to expand...

I believe the limiting factor you're applying here is attempting to use f8 under water. If your results are 3 stops underexposed I'm guessing the camera is going down to 1/30 (slowest shutter speed it may attempt in an AUTO mode) then raising the ISO to 6400 and your results show that isn't enough. I know you want f8 for somewhat deep DOF but under those lighting conditions that just may not be possible once you get to a depth where not much sunlight reaches.

Try f4 and see if you can live with the results, then f2.8. The 12mm focal length should help some with apparent DOF. I assume you can focus somehow but autofocus may not be 100% reliable under those circumstances.

TheTrickster said:
If they would just add AutoISO to the Manual mode (within creative movie) then I would be very happy, as it will only fiddle with ISO - Plus add the upper limit option too!
Click to expand...

The various "hacks" on the GH2 did lift that upper ISO limit, but Panasonic added so much to the GH3 and GH4 there is little incentive to mess with the firmware. I too, wish that ISO limit in Motion Picture was not there, but the GH3 is phenomenal at ISO 6400!
 
Is there a way to take photos in Aperture Priority mode and adjust exposure compensation? With my 60D, I would typically dial it down to -1 stop so my ISO wouldn't go too high.
 
After having a play with the Wifi App (thanks for the tip)...here are my findings... Although the App shows the hidden Aperture, we still don't get to see the ISO value.

Running the camera in Creative Movie Mode with Aperture Priority and AutoISO. The camera tries its best to run a shutter speed twice the frame rate ala 180' shutter angle (I don't think its related at all to focal length of the lens)

Findings:
4K@29.97 - f2.8: We get a Shutter Speed of 80.
4K@29.97 - f4.0: We get a Shutter Speed of 40.
4K@29.97 - f7.1: We get a Shutter Speed of 30.
4K@29.97 - f22: We get a Shutter Speed of 30.

1080@59.94 - f2.8: We get a Shutter Speed of 80.
1080@59.94 - f4.0: We get a Shutter Speed of 60.
1080@59.94 - f7.1: We get a Shutter Speed of 60.
1080@59.94 - f22: We get a Shutter Speed of 60.

4K@23.98 - f2.8: We get a Shutter Speed of 80.
4K@23.98 - f4.0: We get a Shutter Speed of 40.
4K@23.98 - f7.1: We get a Shutter Speed of 25.
4K@23.98 - f22: We get a Shutter Speed of 25.

From this we can say that at no point does the camera take the shutter speed below the currently selected Frame Rate.

Running the Camera in 4K Photo mode - it appears that it prefers to keep the shutter speed at 1/125 and sacrifice ISO - even if the scene is overexposed - I presume to give sharper, less blurrly photos... Sadly only 4K Photo mode gives you the ISO info embedded in the photo file, taking a frame grab from a Creative Movie Mode video, it doesn't contain any EXIF info.
 
TheTrickster said:
After having a play with the Wifi App (thanks for the tip)...here are my findings... Although the App shows the hidden Aperture, we still don't get to see the ISO value.

Running the camera in Creative Movie Mode with Aperture Priority and AutoISO. The camera tries its best to run a shutter speed twice the frame rate ala 180' shutter angle (I don't think its related at all to focal length of the lens)

Findings:
4K@29.97 - f2.8: We get a Shutter Speed of 80.
4K@29.97 - f4.0: We get a Shutter Speed of 40.
4K@29.97 - f7.1: We get a Shutter Speed of 30.
4K@29.97 - f22: We get a Shutter Speed of 30.

1080@59.94 - f2.8: We get a Shutter Speed of 80.
1080@59.94 - f4.0: We get a Shutter Speed of 60.
1080@59.94 - f7.1: We get a Shutter Speed of 60.
1080@59.94 - f22: We get a Shutter Speed of 60.

4K@23.98 - f2.8: We get a Shutter Speed of 80.
4K@23.98 - f4.0: We get a Shutter Speed of 40.
4K@23.98 - f7.1: We get a Shutter Speed of 25.
4K@23.98 - f22: We get a Shutter Speed of 25.

From this we can say that at no point does the camera take the shutter speed below the currently selected Frame Rate.

Running the Camera in 4K Photo mode - it appears that it prefers to keep the shutter speed at 1/125 and sacrifice ISO - even if the scene is overexposed - I presume to give sharper, less blurrly photos... Sadly only 4K Photo mode gives you the ISO info embedded in the photo file, taking a frame grab from a Creative Movie Mode video, it doesn't contain any EXIF info.
Click to expand...

Interesting that your shutter speed stayed high in Photo 4K mode. Were you shooting with a tele lens? Auto-ISO in non-video modes seems to use 1/125 as a floor at longer FL's. My brief test in which SS fell to 1/30th before ISO rose was at 14mm.

Peter
 
Purely unscientific but I've noticed my GH4 try to do smart things in tricky conditions too. Like it definitely lets the shutter speed go way lower using a 45-200 mm lens at 200 mm if the the optical stablisation is switched on, compared with if it is switched off.

Not smart enough for me to trust (at least not yet- maybe in a few years once I've got used to it) but an indication that the Panasonic engineers have put some thought into the auto settings, at least. That trust would come much more quickly for me if I could see exactly what the camera was setting in auto modes, all the time, as others have said.

All in all though I'm continuing to be impressed by the little GH4, so much so that I'm considering taking it as my main camera on forthcoming trip to Norway.

Cheers, Hywel
 
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