shutter speed vs. aperture at DVinfo.net

Buck Admas · November 13th, 2009, 11:57 AM

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.

Steve Phillipps · November 13th, 2009, 04:48 PM

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).
Steve

Nik Skjoth · November 13th, 2009, 05:35 PM

right... Try recording running water and go from 1/60 gradually up to 1/1000, you'll see why you wanna keep it low.

Chris Hurd · November 13th, 2009, 07:15 PM

Quote:

Originally Posted by Buck Admas

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.

Liam Hall · November 14th, 2009, 05:52 AM

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.

David Chapman · November 14th, 2009, 10:45 AM

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.

Nigel Barker · November 14th, 2009, 03:12 PM

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

Nigel Barker · November 14th, 2009, 03:14 PM

Quote:

Originally Posted by Steve Phillipps

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.

Steve Phillipps · November 14th, 2009, 03:44 PM

Yes of course, but in PAL land 1/2 shutter would be 1/50th as you'd be shooting 25P.
Steve

Liam Hall · November 14th, 2009, 03:49 PM

Quote:

Originally Posted by Nigel Barker

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.

Nigel Barker · November 15th, 2009, 02:50 AM

Quote:

Originally Posted by Liam Hall

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.

Liam Hall · November 15th, 2009, 08:44 AM

Yes, well pretty much yes. The theory isn't perfect.

Here's a good explanation.

DOF2

Buck Admas · November 16th, 2009, 09:04 PM

cool. thanks for all the help guys

November 13th, 2009, 11:57 AM	#1
Buck Admas New Boot Join Date: Nov 2009 Location: Canada Posts: 7	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.

November 14th, 2009, 05:52 AM	#5
Liam Hall Major Player Join Date: Sep 2006 Location: London, England Posts: 969	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. __________________ Writer-Director-DOP www.liamhall.net

November 14th, 2009, 10:45 AM	#6
David Chapman Major Player Join Date: Mar 2006 Location: Dallas, TX Posts: 346	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. __________________ David Chapman www.davechapfilms.com

November 15th, 2009, 08:44 AM	#12
Liam Hall Major Player Join Date: Sep 2006 Location: London, England Posts: 969	Yes, well pretty much yes. The theory isn't perfect. Here's a good explanation. DOF2 __________________ Writer-Director-DOP www.liamhall.net

November 13th, 2009, 04:48 PM	#2
Steve Phillipps Inner Circle Join Date: Apr 2006 Location: Wales Posts: 2,130	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). Steve

November 13th, 2009, 05:35 PM	#3
Nik Skjoth Regular Crew Join Date: Jul 2007 Location: Cph Denmark Posts: 136	right... Try recording running water and go from 1/60 gradually up to 1/1000, you'll see why you wanna keep it low.

November 14th, 2009, 03:12 PM	#7
Nigel Barker Inner Circle Join Date: Feb 2009 Location: Norwich, Norfolk, UK Posts: 3,531	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

November 14th, 2009, 03:44 PM	#9
Steve Phillipps Inner Circle Join Date: Apr 2006 Location: Wales Posts: 2,130	Yes of course, but in PAL land 1/2 shutter would be 1/50th as you'd be shooting 25P. Steve

November 16th, 2009, 09:04 PM	#13
Buck Admas New Boot Join Date: Nov 2009 Location: Canada Posts: 7	cool. thanks for all the help guys