Low Apertures and ND Filters

[Tim Davison]

I am using Tiffen 0.9 ND Filters on my lenses when shooting outdoors to try and get the f stop as low as possible but finding that I am often having to really push up the shutter speed to avoid over exposure in bright sunshine.

I know the conventional wisdom says that shutter speed should be twice the frame rate to avoid shots being too 'choppy' but just how bad is it up the shutter speed to maintain depth of field? Should the aperture or the shutter speed be sacrificed first in your opinion? Do you use stronger ND filters?

I am thinking of buying a polarising filter (to combine with my ND filter) to assist with this process.

[Les Wilson]

My experiments with polarizers showed a loss of about 1 stop no matter how it was oriented.

I have no experience with HDSLRs outside yet but what was recommended to me was to have both a .9 and .6 on hand and use them together or with a polarizer to get the aperture you want.

I assume you are lowering the ISO to 100 already.

[Jeremy Pevar]

Do not, I repeat, DO NOT adjust shutter speed to get the correct exposure when shooting video on the 7D (or 5D, or any DSLR.) When shooting video on these cameras there are two ways to adjust the amount of light entering the camera: 1. Adjust the f-stop, 2. Add an ND filter

If you are shooting at ISO 100 with a 1/50th shutter speed in full sunlight you will need 4 - 6 stops reduction in light. So, either you will need to stack several ND filters, or you will need one much darker ND filter. I would recommend dropping a few hundred dollars and buying a variable ND filter (Tiffen just came out with one that sells for $250.)

The reason that you shouldn't change shutter speed to control exposure is that it will effect the look of the image by greatly reducing motion blur. Sometimes this is desirable (see the beach scene in Saving Private Ryan for a great example of this effect,) but often it is not.

I would strongly recommend picking up a book on cinematography to learn the basics. An invaluable reference is the ASC Manual - every DP in Hollywood has a copy of this book in their kit.

Good luck!

[Chris Westerstrom]

i agree it looks choppy to increase shutter speed, but in a pinch it's far better than the moire problem that is amplified 10X when stopping down.

ND filters are definitely preferable but stopping down is not always an option in the DSLR world IMO...especially when shooting architecture exteriors.

I guess it's a matter of preference but with a wide angle exterior, I'd rather have choppy sharpness than nasty moire.

I also think plenty of things can look appealing with higher shutter speeds

[Pedanes Bol]

With a fixed shutter speed of 1/50 and an open aperture, your options to achieve desired exposure include ND filters and adjusting the ISO. I typically use ND 0.6 and 0.9 filters either alone or in combination depending on the available light and then change the ISO if needed (like adjusting GAIN in a camcorder).

Hope this helps.

P.

[Tim Davison]

All very helpful guys, thanks. Variable ND filter seems to be the way forward but, as I will not ahve time to purchase one before the weekend, I think I will have to double up on the ND filters that I have and hope that does the trick

[Liam Hall]

Stacking NDs if fine. Buying a stronger ND is better. Try getting a 1.5 or a 1.8. On a sunny day, shooting at 1/50th/ISO100 with a 1.5ND will get you to f/4, with a 1.8 will you'll to f2.8.

Variable NDs have their uses, but can give inconsistent colour and as cause refraction at longer focal lengths. I avoid using mine whenever I can.

[Bill Pryor]

I have a .9 and a .6 ND (both B+W filters) and usually stack them in bright sun.

[John Wiley]

Originally Posted by Jeremy Pevar

Do not, I repeat, DO NOT adjust shutter speed to get the correct exposure when shooting video on the 7D (or 5D, or any DSLR.) When shooting video on these cameras there are two ways to adjust the amount of light entering the camera: 1. Adjust the f-stop, 2. Add an ND filter

If you are shooting at ISO 100 with a 1/50th shutter speed in full sunlight you will need 4 - 6 stops reduction in light. So, either you will need to stack several ND filters, or you will need one much darker ND filter. I would recommend dropping a few hundred dollars and buying a variable ND filter (Tiffen just came out with one that sells for $250.)

The reason that you shouldn't change shutter speed to control exposure is that it will effect the look of the image by greatly reducing motion blur. Sometimes this is desirable (see the beach scene in Saving Private Ryan for a great example of this effect,) but often it is not.

I would strongly recommend picking up a book on cinematography to learn the basics. An invaluable reference is the ASC Manual - every DP in Hollywood has a copy of this book in their kit.

Good luck!

I think you're taking the 180 degree rule a little too seriously! I agree that if in doubt you should stick to 1/50th wherever possible, but there are also plenty of times to bend this rule. I shoot lots of surfing and it looks terrible at 1/50th. I'll often push the shutterspeed up to 1/200th or even higher to get a sharper look. Likewise I've seen examples where Stillmotion, one of the most respected production companies using DSLR's to shoot weddings, often bump up their shutterspeed to allow a wider aperture in bright sunlight.I suppose they know they can get away with it because the minimal motion in during the ceremony or posed shots means very few people will notice any sort of difference in the motion blur.

Rules where made to be broken... by all means learn the guidelines and the reasons behind them, but do not limit yourself creatively and technically by sticking to them till the death.

[Nigel Barker]

Evidently Polaroid (who presumably know a thing or two about polarising materials) now make a full range of variable ND filters at cheap prices. I have just ordered a few to see how they perform.

Amazon.co.uk: polaroid variable nd

 

Amazon.co.uk: polaroid variable nd

Polaroid Polaroid Variable Range Fader Filter - Digital Imaging Accessories

[Greg Fiske]

+1 to John's comment. The 5d can go down to 50 iso. Another option, if you are ok with a 720p deliverable is doing slow motion so you can use 1/120.

I would put more weight to maintaining shutter speed. Nothing really wrong with having your background included in your frame, just get creative with your composition/ look for interesting or basic backgrounds.

[Nigel Barker]

The 5DII can go down to ISO 50 only when shooting stills you cannot use it in movie mode.

[Jimmy Toha]

Originally Posted by Nigel Barker

Evidently Polaroid (who presumably know a thing or two about polarising materials) now make a full range of variable ND filters at cheap prices. I have just ordered a few to see how they perform. Amazon.co.uk: polaroid variable nd
Polaroid Polaroid Variable Range Fader Filter - Digital Imaging Accessories

Nigel, when you've received it, do share with us what you think about it.

Some reviews from Amazon aren't exactly stellar but then again, it's fair to listen to more than one or two opinions :)

[Tim Davison]

In the end I went for the Light Workshop Variable NND Filters (about £100 in the UK) and must say I've been really impressed with the reults