How does XF400 handle shutter speed and gain in aperture priority?

[Nick Mirro]

I am unsure about the handling of SS, aperture and gain. If I want to control aperture, how does the camcorder apportion exposure correction between SS and gain?

Can I lock SS and aperture, and have the camcorder use auto gain? I understand manual will give full control, but I don't want to chase the exposure needle if the camera can adjust gain automatically.

I guess I'm trying to keep the correct SS to framerate ratio while controlling DOF.

[Nick Mirro]

I suspect that nobody knows quite what the camcorder does with gain and SS in this situation.

As for auto ISO, this article explains things. https://forums.creativecow.net/thread/59/863249

Since I am shooting living moving creatures and filming while boating (moving), I guess I need to shoot manual and keep my hand on the gain and keep the needle in the middle. I don't like not knowing what the SS is.

[Ron Evans]

Not sure how the XF400 does it but on my Sony and Panasonic if I set iris and shutter speed , with gain limit ( so the camera doesn`t try and see in the dark ) gain set to auto , I then set how I want the image to look with AE shift controls. Auto gain will try and maintain that look. Clearly if the image goes very dark or very light it will not work too well but most of the time it works well. Cameras currently are Sony AX100, AX53 and Panasonic GH5 and GH5S.

[Nick Mirro]

Thanks for sharing your experience. This missing feature is a bummer. Canon only gives gain control limit.

Do you think Canon would allow SS to be significantly out of ratio with framerate, just to keep the right exposure? Things would get too choppy or fluid. Maybe I'll post this to Canon.

[Ron Evans]

You have AE on the XF400, page 72 in the manual that I downloaded the only problem is it is only operational in P, Tv or Av so you will not be able to set shutter and iris and let it control gain. Personally I do not like shutter speed changing so I do not think you can have complete control of depth of field and shutter speed.

[Nick Mirro]

I agree. So manual mode it is with the custom dial set to adjust gain. Thank you! :)

In SS priority, I'm left wondering if gain is adjusted at all in light of the composition, or if the camera just varies aperture to get the best EV.

Though it is customizable, I'm coming to realize this camcorder is directed more to users wanting minimal tweaking and minimal post-processing.

[Ron Evans]

I think it will adjust aperture and gain so setting a gain limit will also restrict the range it uses and the AE control will then try and maintain brightness of image to what you have set. If it is like the smaller Sony`s it will try and set the aperture to the lens sweet spot and use gain to change the image.

[Bryan Worsley]

Haven't used an XF400 myself, but on the HF-GXX camcorders I've owned you could confirm the actual shutter and aperture values chosen by the camcorder in the programmed exposure modes (P, Av, Tv) by taking a Photo. Upon pressing the on-screen Photo icon, the values would momentarily flash on screen.

[Nick Mirro]

Thank you Bryan. Shooting pictures does bring up the aperture and SS. I can see that in SS priority, aperture is adjusted first. Then gain is applied to the limit set as Ron said. In manual exposure, auto gain will not function. So the only way to get a small aperture in SS priority is to flood the subject with light. That is possible in my case. Thanks for the help here!!!

[Ron Evans]

Remember the zoom will also ramp aperture. Not sure how much on the XF400 but on my Sony's and the Panasonic zooms on the GH it ramps quickly so if you are after shallow depth of field that will be difficult. I spend most of my time at the opposite end getting the max depth of field in the theatre. Sad that it will not allow you to set aperture and shutter speed with it managing gain as both my GH and my Sony AX100 will do that.

[Bryan Worsley]

Originally Posted by Nick Mirro

In manual exposure, auto gain will not function. So the only way to get a small aperture in SS priority is to flood the subject with light.!

I took that to mean Nick is after deeper depth of field (closing down the iris), assuming he's shooting at full wide angle ?

Surely this can be managed in full Manual Exposure mode ? Yes the AGC function is disabled, as you would expect, but after setting the desired SS and Aperture you can still manually adjust the level of Gain. That's how it works on my HF-G30 and checking the XF-400/405 manual on-line (page 68) it's the same. In Manual Exposure mode, the chosen Gain level is imposed and independent of SS and Aperture i.e. it's not setting an AGC limit. Rule of thumb, at least on the older XA/HF-G models, was that a 6db change in Gain equates to one f-stop.

On the XF-400/405 you also have an exposure assist tool (Exposure Bar, page 69) that shows the optimal automatic exposure (that the camcorder would set) and the current (manually set) exposure and an indicator on the bar flashes when the difference is greater than +/- 2 EV.

Of course, if you are adding Gain to compensate for closed down aperture it's going to be at the expense of increased noise levels. "Flooding the subject with light" might be the better way to go.

[Bryan Worsley]

Incidentally, on the older (HD) XA/HF-G models there was an additional option (under 'Image Effects') for making fine exposure ('Brightness') adjustments (on an arbitrary +/- 2 scale) when recording in the programmed exposure modes. I examined this on my HF-G30 a while back using the photo trick to reveal the SS and Aperture values. Just checked it again. Interesting that when recording in P mode (under adequate/optimal lighting) it makes small adjustments to the aperture value only - doesn't touch the internally set SS. In low l light, with the iris fully open (F1.8), I assume it resorts to Gain.

On the latest 4K models (XA50/55, HF-G60) with the 1" sensor, I see that this 'Brightness' setting is no longer available. The available image adjustment options (now under 'Looks') are limited to Sharpness, Contrast and Color Depth (Contrast being disabled in Wide DR). And likewise on the XF400/405 and GX10. That said, these models do give a much wider range of incremental aperture and SS settings to choose from. One frustration I have with my HF-G30 is that it is not possible to manually set a 1/120 sec shutter (in Tv or Manual exposure modes) when recording at 1080p60.

[Ron Evans]

Is there a reason you want to set 1/120 for 60P ?

[Bryan Worsley]

To achieve a '180 degree' motion blur, as suits the subject matter and lighting conditions. I shoot a fair amount of indoor sports. The irony is that the camcorder will internally target a 1/120 shutter in fully automatic (P) exposure mode (as revealed by the Photo trick) under the same conditions.

[Ron Evans]

The 180 degree shutter rule was an upper limit to reduce the judder of slow frame rate film making at 24fps or slower. Deliberately set to induce motion blur. I do not think that is necessary when the frame rate is above 48fps the perceived flicker rate for our eyes. If you want to use stills from the video that is another issue and the faster rate would be helpful for that. All my video is indoors too and I always shoot with 1/60 at 60P. Gives a little more light too and if you really want the slower frame rate look in editing on a 30P timeline then shutter speed is fine for that too. Placing the 60P video with 1/120 shutter on a 30P timeline you would get judder.