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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


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Old November 13th, 2009, 11:57 AM   #1
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shutter speed vs. aperture

during bright daylight shooting in photo and video mode, what are benefits of using ND filter for shallow DOF photography vs. achieving correct exposure by increasing the shutter speed to match a wide open aperature?

i'm newish to the DSLR thing and still trying to understand. Also, when shooting video with different lenses, how can i make sure the footage has even exposure and DOF across both lenses without a lightmeter and exposure chart? Thanks.
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Old November 13th, 2009, 04:48 PM   #2
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In movies if you use too fast a shutter speed the image strobes quite irritatingly. Rule is to use a shutter speed double the frame rate (ie 1/60th second at 30fps).
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Old November 13th, 2009, 05:35 PM   #3
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right... Try recording running water and go from 1/60 gradually up to 1/1000, you'll see why you wanna keep it low.
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Old November 13th, 2009, 07:15 PM   #4
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Originally Posted by Buck Admas View Post
how can i make sure the footage has even exposure and DOF across both lenses without a lightmeter and exposure chart? Thanks.
Manually set an aperture value at or below the maximum aperture of the slowest lens.

For example, if you have these lenses:

EF 50mm f/1.8
EF 70-200mm f/4L
EF 28-135mm f/3.5-5.6

The maximum aperture value of the slowest lens will be f/5.6 at the full telephoto end of the EF 28-135mm lens. Therefore you'll want to manually set an aperture value of f/5.6 or slower no matter which of these three lenses you're using.
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Old November 14th, 2009, 05:52 AM   #5
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That will work for depth of field but not exposure Chris. These are f/stops not t/stops. The light transmission will vary between lenses at the same f/stop. Zoom lenses in particular will vary greatly compared with primes and you could quite easily find yourself missing exposure by a stop, which on a digital camera could be crucial.

I suggest the OP learns the histogram and how to use it. That will tell him exactly what is going on.
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Old November 14th, 2009, 10:45 AM   #6
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Liam, I noticed this a few weeks ago when I got the 50mm f/1.4. I took a photo with that lens at 2.8 and then another photo with my 17-55mm f/2.8 (trying to match focal length) and the 50mm appeared to be a stop brighter (at least a half) at the same aperture setting.

The histogram and exposure readings in the camera should help produce a good exposure for each photo/video. Any other details can be adjusted in post.
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Old November 14th, 2009, 03:12 PM   #7
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The depth of field depends on several factors including aperture, the focal length of the lens & the distance of the subject. Keeping a constant aperture while changing to a lens of a different focal length will not maintain the same DOF. See here for an interactive calculator Online Depth of Field Calculator
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Old November 14th, 2009, 03:14 PM   #8
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Originally Posted by Steve Phillipps View Post
Rule is to use a shutter speed double the frame rate (ie 1/60th second at 30fps).
If in PAL land with 50Hz power then the shutter speed should be 1/50 to avoid flickering under artificial lights.
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Old November 14th, 2009, 03:44 PM   #9
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Yes of course, but in PAL land 1/2 shutter would be 1/50th as you'd be shooting 25P.
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Old November 14th, 2009, 03:49 PM   #10
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Keeping a constant aperture while changing to a lens of a different focal length will not maintain the same DOF. [/url]
It will if you change subject to camera distance by the appropriate amount.
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Old November 15th, 2009, 02:50 AM   #11
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It will if you change subject to camera distance by the appropriate amount.
Agreed so if you switch from a 50mm to a 100mm lens then if you double the subject to camera distance will the DOF remain the same for the same aperture. Aperture, subject distance & lens focal length are the variables in the equation but sensor size which is the other factor in the calculation will remain constant for a given camera.
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Old November 15th, 2009, 08:44 AM   #12
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Yes, well pretty much yes. The theory isn't perfect.

Here's a good explanation.

DOF2
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Old November 16th, 2009, 09:04 PM   #13
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cool. thanks for all the help guys
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