Regarding overexposure - a tip

[jparnold]

In the past couple of years I have noticed that sometimes very brightly lit scenes appear to be overexposed by my Vidcam (Panasonic GS400).

Recently I had an idea and so checked what the camera was automatically setting the shutter speed (usually 1/50 second) and iris /aperture for very brightly lit scenes (eg beach, snow, desert). I can do this as my Vidcam has auto and manual settings of all sorts of things including shutter speed, iris/aperture and white balance.
My camera had 'set' the camera to 1/50 f16.
I then manually set the shutter speed (using shutter priority) to 1/125 to see what the iris/aperture would do (it was still being automatically set) and nothing happened. I then set the shutter speed to 1/250. The iris/aperture then 'opened' from f16 to f11.
What did this tell me?
The optimum shutter speed at f16 (the max) was 1/125. So at 1/50 (the default automatic speed) and f16 (the max) I was overexposing.

The moral of this post?

If you have a Vidcam which allows manual settings check this out especially if the maximum aperture for your camera is f16.

Use a Neutral Density filter (say X4) attached to the front of the lens BUT remember to remove it when videoing dimly lit scenes.

This saves having to darken a video clip using Brighness/contrast (VideoStudio) 'filter'.




I recently checked the aperture setting on my VidCam when 'filming' in desert areas (my Vidcam is auto as well as manual) and I noted that the aperture had been set (automatically) to f16 the highest aperture available (the auto shutter speed is 1/50). I then manually set the shutter speed (leaving the aperture to be automatically set) and it wasn't until I set the shutter speed to 1/250 before the aperture changed (from f16 to f11).
The 'moral' of this is that I was OVER EXPOSING when using fully auto mode (1/50 f16). I had noted previously that some scenes/clips seemed over bright and had to adjust using a video filter during editing to darken them.
So I now use a X4 ND (neutral density) filter for brightly lit scenes.

[GLOBETROTTER]

I most often set my video camera to 1/50 because this is the optimum shutter spead for video with normal motion (especially for Pal video) and ISO at 160 for optimum fine grain without pixel noise. The aperture is also set at f/8 for optiumum lens quality and sharpness & DOF across the frame, only opening to a wider aperture such as f/2.8 to throw the background out of focus and accentuate the subject in sharp focus.
This means that the SHUTTER speed of the camera remains constant and the APERTURE setting on the lens iris is adjusted for light and or FOV and depth of field changes/requirements. Unlike when I often stop the aperture down to f/16 or f/22 for still images of landscapes, I rarely stop the aperture down beyond f/8 in video mode, because this will often cause lens 'softness' of the video image and less clarity across the frame.

This works well for most even lighting or overcast weather in northern climate countries, but in very bright sunlit conditions when the frame becomes over-exposed it can be impossible to prevent the aperture from shutting down to f/16 or beyond, so to prevent this problem and still be able to keep your aperture at f/8 or at wider settings (f/1.2 to f/8), simply screw an ND filter to the front of the lens.
For widely changing light conditions, you can also use a Variable ND filter. For static landscape video footage where you have dark foreground and bright sky/background, a Graduated ND filter works wonders.
I actually prefer to use a Circualar Polariser filter on front of lens for most of my outdoor video fotage, and that same PL filter also acts as a natural ND filter.

So to clarify, do NOT simply close your aperture down to f/16 or f/22/ or f/32 when shooting video (unless you are filming 1/1 Macro subjects). For most normal filming, use an ND or PL filter to block bright light levels and enable you to keep that lens iris open at wide to medium apertures (depending on your subject matter).

[jparnold]

Thanks for those tips.
I was aware that the optimum shutter speed for video is 1/50 (I have tried faster shutter speeds and with fast moving objects like a birds wings in flight you get almost a strobe effect with faster shutter speeds).
Also I was aware use of the iris/aperture to control DOF (I am casting my mind back to when I used an (film) SLR).

I rarely stop the aperture down beyond f/8 in video mode, because this will often cause lens 'softness' of the video image and less clarity across the frame.

I was unaware of this.

So to clarify, do NOT simply close your aperture down to f/16 or f/22/ or f/32 when shooting video (unless you are filming 1/1 Macro subjects).

I usually rely on auto allowing the camera to choose the relevant white balance and also aperture as most of the time I don't have time to set these manually.

you can also use a Variable ND filter.

I was unaware these existed and would be great for many reasons especially not having to remove the ND filter in certain situations.

The reason for my post was to bring to the attention of readers who only have fully automatic cameras (and those who can manually set their cameras but use auto most of the time) that in extremely brightly lit scenes it is possible to overexpose without a ND filter (because at 1/50 and max iris/aperture too much light can still get through).

[39_Steps]

Thanks to both for these tips and hints. I just checked the seldom used manual for my seldom used Canon HF 100 1080i camera to see if any internal ND filters exist. Apparently not, but it might be helpful if they did.

In video mode, these are the options;
-aperture: [1.8], [2,0], [2.4], [2.8], [3.4], [4.0], [4.8], [5.6], [6.7], [8.0]
-shutter: [1/2000], [1/1000], [1/500], [1/250], [1/100], [1/60], [1,30], 1/15], [1/8]

The Beach and Snow settings apparently throw in a little extra overexposure so that faces will not be underexposed! It is not clear to me whether use of the 24 fps "filmlike' Cine setting would cause any additional overexposure, but perhaps the 30P fps and 24P fps modes are just variations on the interlaced 60fps option.

Thanks again for the hints.