stupid DOF question for xl1s at DVinfo.net

JT Coleman · August 19th, 2006, 12:14 PM

sorry for the stupid question, but is there a way to make your DOF more shallow with an XL1s? I don't like that my images always turn out so flat.

JT Coleman
Austin, Texas

Rob Lohman · August 19th, 2006, 12:16 PM

Try opening up your iris (low f-stop) and zoom in on your subject.

If there is a lot of light you may need to increase shutter speed
or add ND filters (or lower the light levels in another way).

Cole McDonald · August 19th, 2006, 12:42 PM

in addition to opening the iris, you need to put more distance between your subjects and their backgrounds. With the camera closer to your subjects, you will get a tighter DoF. DoF gets shallower the closer to the lens you get. If you can get the subject the closest to the lens you can afford to get the framing you need, you will have the most focal control. DoF on a small chip still is longer than you want, so give plenty of space behind the subjects.

Chris Hurd · August 19th, 2006, 12:55 PM

Also see http://www.dvinfo.net/articles/optics/dofskinny.php

JT Coleman · August 19th, 2006, 04:28 PM

Quote:

Originally Posted by Cole McDonald

in addition to opening the iris, you need to put more distance between your subjects and their backgrounds. With the camera closer to your subjects, you will get a tighter DoF. DoF gets shallower the closer to the lens you get. If you can get the subject the closest to the lens you can afford to get the framing you need, you will have the most focal control. DoF on a small chip still is longer than you want, so give plenty of space behind the subjects.

So the iris change totally worked, thanks for that... on your suggestion, Cole, I can't seem to find a way to get a notable change in my DOF by moving the subject closer to the lens. When I do, I inevitably had to zoom out in order to make them match the necessary frame size, and that unfortunately increases my DOF and puts me right back where I started. I read about this in the ultimate DOF skinny, so I guess thats normal, but is there some other trick I'm not thinking of?

I guess another way to read your suggestion is "try and place your subjects so that the background falls outside the DOF and this will also reduce the flatness of your image" ...?

Btw guys, thanks again for the help !!!

JT Coleman
Austin, Texas

Nick Weeks · August 19th, 2006, 04:32 PM

The further you zoom in, the better DOF, so, move your camera back far away from the subject, and put the background far away, then zoom in as far as it's feasable... combine this with a large iris and you have a nice DOF

That's what makes these cameras and lenses so difficult to get good DOF because you can't always move the camera that far back and zoom in

Another problem is I think the IS II auto lens that comes with the XL1s ramps up the iris as you zoom in, so you can't do 1.6 at full zoom I don't think. I'm using the 16x manual on mine, so I can't tell you for sure.

Cole McDonald · August 19th, 2006, 05:29 PM

How close were you to your subjects? I'm thinking 4 feet or less. The two options for camera placement are:

1) uncomfortably close to the subject (see the BTS in "Signs" by M. Night Shamamamamamalalalalman...look at how close the camera is to the talent at the dinner table)

2) a block away at full zoom. This brings the out of focus background close enough that you can see it's out of focus, but if you put someone in front of a tree, the leaves will be the size of their head due to the magnification caused by being zoomed in.

In addition to that, the farther away the camera gets, the longer the focal range, so getting shallow DoF becomes more difficult. Which it already is when shooting on a 7mm chip (1/3 inch). The physics of lenses dictate that the in focal range in creases the further away from your lens.

The best way to figure out the optimal placement is to do some tests using a tape measure from lens to subject and beyond them to the background. Start near the camera (1 foot), wide as the lens will go and write down the tape measure points where focus fades in front and behind the subject. Move the subject back a foot and repeat until you can no longer get them to go out of focus when they move backwards after you've focused on them in place.

Then zoom in about half way and repeat...you'll note that the focal range is unaffected by the zoom, all it does is exxagerate the out of focus background by magnifying it...zooming also serves to flatten the 3-d quality of your scene:

Cam----------Sub----------Back (wide)
Cam-----Sub-----Back (2x zoom)

You will not that the background is brought optically closer to the camera than is the subject...you distort space by zooming and flat is what you are trying to avoid...so have your actors get used to being able to reach out and touch the camera when they are doing their sides. I am, of course, assuming you are using this for narrative shooting where you have control over the environment and blocking and actors.

Justine Haupt · September 4th, 2006, 09:03 AM

Of course, on a thread like this, somebody has to point out mini35 adapters... skim the "Alternative Imaging Methods" board for more info.

If you have an "extra" $1000 to throw around, there are some great solutions.

August 19th, 2006, 12:14 PM	#1
JT Coleman Regular Crew Join Date: Nov 2005 Posts: 32	stupid DOF question for xl1s sorry for the stupid question, but is there a way to make your DOF more shallow with an XL1s? I don't like that my images always turn out so flat. JT Coleman Austin, Texas

August 19th, 2006, 12:16 PM	#2
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Try opening up your iris (low f-stop) and zoom in on your subject. If there is a lot of light you may need to increase shutter speed or add ND filters (or lower the light levels in another way). __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

August 19th, 2006, 12:42 PM	#3
Cole McDonald Trustee Join Date: Nov 2005 Location: Sauk Rapids, MN, USA Posts: 1,675	in addition to opening the iris, you need to put more distance between your subjects and their backgrounds. With the camera closer to your subjects, you will get a tighter DoF. DoF gets shallower the closer to the lens you get. If you can get the subject the closest to the lens you can afford to get the framing you need, you will have the most focal control. DoF on a small chip still is longer than you want, so give plenty of space behind the subjects. __________________ Web Youtube Facebook

August 19th, 2006, 12:55 PM	#4
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	Also see http://www.dvinfo.net/articles/optics/dofskinny.php __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

August 19th, 2006, 05:29 PM	#7
Cole McDonald Trustee Join Date: Nov 2005 Location: Sauk Rapids, MN, USA Posts: 1,675	How close were you to your subjects? I'm thinking 4 feet or less. The two options for camera placement are: 1) uncomfortably close to the subject (see the BTS in "Signs" by M. Night Shamamamamamalalalalman...look at how close the camera is to the talent at the dinner table) 2) a block away at full zoom. This brings the out of focus background close enough that you can see it's out of focus, but if you put someone in front of a tree, the leaves will be the size of their head due to the magnification caused by being zoomed in. In addition to that, the farther away the camera gets, the longer the focal range, so getting shallow DoF becomes more difficult. Which it already is when shooting on a 7mm chip (1/3 inch). The physics of lenses dictate that the in focal range in creases the further away from your lens. The best way to figure out the optimal placement is to do some tests using a tape measure from lens to subject and beyond them to the background. Start near the camera (1 foot), wide as the lens will go and write down the tape measure points where focus fades in front and behind the subject. Move the subject back a foot and repeat until you can no longer get them to go out of focus when they move backwards after you've focused on them in place. Then zoom in about half way and repeat...you'll note that the focal range is unaffected by the zoom, all it does is exxagerate the out of focus background by magnifying it...zooming also serves to flatten the 3-d quality of your scene: Cam----------Sub----------Back (wide) Cam-----Sub-----Back (2x zoom) You will not that the background is brought optically closer to the camera than is the subject...you distort space by zooming and flat is what you are trying to avoid...so have your actors get used to being able to reach out and touch the camera when they are doing their sides. I am, of course, assuming you are using this for narrative shooting where you have control over the environment and blocking and actors. __________________ Web Youtube Facebook

August 19th, 2006, 04:32 PM	#6
Nick Weeks Major Player Join Date: Jan 2006 Location: Birmingham, AL USA Posts: 722	The further you zoom in, the better DOF, so, move your camera back far away from the subject, and put the background far away, then zoom in as far as it's feasable... combine this with a large iris and you have a nice DOF That's what makes these cameras and lenses so difficult to get good DOF because you can't always move the camera that far back and zoom in Another problem is I think the IS II auto lens that comes with the XL1s ramps up the iris as you zoom in, so you can't do 1.6 at full zoom I don't think. I'm using the 16x manual on mine, so I can't tell you for sure.

September 4th, 2006, 09:03 AM	#8
Justine Haupt Major Player Join Date: Oct 2005 Location: Long Island, NY Posts: 208	Of course, on a thread like this, somebody has to point out mini35 adapters... skim the "Alternative Imaging Methods" board for more info. If you have an "extra" $1000 to throw around, there are some great solutions. __________________ ~Justine "We are the music makers, and we are the dreamers of dreams" -Arthur O'Shaunessey (as quoted by Willy Wonka)