Cheap 77mm ND filter to shoot budget skiing videos..

[Mogul]

I'm normally quite happy with stabilised iPhone 4S video when shooting the kids skiing but might try the 600D this year if it isn't too much hassle.

Would use the 17-40mm f/4L at f22 but still probably too much light about to achieve a slow shutter speed for smooth video so thinking about a el-cheapo ND filter off eBay just for fun.

Assuming that I'll be able to run a custom white balance it and get reasonable results for video with a cheap one. Anyone got any other pointers??

[tenohfive]

Personally I don't believe in putting bad glass in front of good - the end result will only be as good as the weak link.

[Mogul]

With you on that but this is just for a bit of fun... Was thinking that any objective loss in image quality (on a frame by frame basis) would be outweighed by the perceived quality of smooth video and the ability to shoot wide open for some depth of field.

[Super Slo Mo]

Wide open gives you very little depth of field. Having said that, on snow I'd expect you to be stopped down a bit anyway, even using ND.

[Mogul]

Should have said that *shallow* depth of field was what I would like to achieve..

40mm @ f/4 on my crop sensor with a subject at 10 ft should have some useful shallow depth of field

Depth of field
Near limit 8.75 ft
Far limit 11.7 ft
Total 2.92 ft

I think I'll just by an el-cheapo variable ND and give it a go. ND400 should let me play with f/4?


http://goo.gl/G8gbse

[Simpo Two]

What shutter speed are you trying to get?

[Super Slo Mo]

At s guess, below 1/60th if he's wanting it to be 'smooth', although even at this shutter speed there'll still be a noticeable effect.

[Mogul]

Have assumed that shooting video for playback at 24fps, the longest possible shutter speed might be 30fps and that might be worth going for.

e.g. for each second of footage, you would 'see' 24 x 1/30ths and this would look quite different to 24 x 1/4,000ths but if a single shot was well exposed at 1/4,000ths, I believe that I would need to come down 7 stops to let the same amount of light in at 1/30th..

[Super Slo Mo]

1/4000 is one heck of a shutter speed. I don't know the number of stops offhand but you're probably right.
At that frame rate even 1/125 will be noticeable.
The only thing to bear in mind is that at the lower shutter speeds you might get a smeary picture due to camera shake or motion blur. There's an easy way to find that out though.