depth of field & filmmaking - help

stephenlevi

stephenlevi

Just a little background, I am a photographer, so I understand depth of field, shutter speed, ISO, etc.

The part that is confusing me is this. When filming at 24fps and a constant shutter speed of 50, if you go outside and its very bright, it's virtually impossible to get a nice shallow depth of field shot at say f4. Because it's too bright.

For example, today I was messing with the video on my DSLR and went outside and turned the ISO all the way down, shutter on 50, and it's way too bright. From what I've been told, you don't want to mess with shutter speed in filmmaking, because movie cameras shoot at 48 (50 being closest on DSLR) otherwise it won't keep that filmic look.

I'm confused.

So basically with filmmaking, am I just supposed to rely on aperture, ISO and ND filters?
 
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Theodebernacius said:
The human eye cannot see IR. Can sensors "see" IR? What does he mean by "blue-light-sensitive chip"?
Click to expand...

Camera sensors generally can see IR, and have filters in place to cut it out so it doesn't effect the image - but most cameras still have some small sensitivity to IR and as Knightly mentioned you can test for it with a tv remote.

Also, most digital sensors are less sensitive to blue than to red and green. As a result the blue channel signal typically needs more gain than the other two to create a balanced image, and so the blue channel tends to be much noisier than the others.

So my best guess at what he's talking about is that when they filmed outside they were using the IR NDs to cut out the remaining IR light that was being seen by the sensor. IR mostly affects the red channel, by cutting it down they were able to increase the overall exposure to get more light for the blue channel without overexposing the red channel.

Now the effects of that are probably minimal as far as anyone's concerned who isn't shooting for the absolute cleanest image for theatrical blow-up. But the concept is relevant to the rest of us in a different situation - indoor lighting. If you are shooting with something like a DSLR, and you are shooting indoors in relatively low light, you can minimize the visible noise in your image by using lights with a stronger blue component - i.e. daylight balanced. Swap incandescent practicals for daylight balanced CFLs, then use either daylight LEDs or Flourescent for your additional lighting. It's not a huge difference but it's worth testing to see if it's worth the trouble for your particular needs.
 
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If you can afford a more expensive filter ($100 on eBay, $300 name brand) a variable ND will be your best friend and last a lifetime.

Stay away from the super cheap ND filters (under $25 a pop) on eBay and such. I bought a few $6 and $7 knowing they'd be bad "but surely not that bad, right?". Turns all my footage pink and don't live up to their ND rating.

A typical decent filter runs $35-60 at a brick and mortar camera store.
 
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