View Full Version : depth of field


michael
01-13-2004, 06:52 PM
does anyone know how to increase a DV camera's (such as the Canon XL1S) depth of field?

-thanks in advance for any responses

indietalk
01-13-2004, 07:42 PM
Physically move the camera forward, and go wider.

film8ker
01-16-2004, 02:15 PM
Use higher quality lenses. Decrease the light and open the iris. For more info and depth of field and circle of confusion read the “Filmmaker’s Handbook.”

Shot Renegade
03-27-2004, 07:34 PM
Neutral Density filters are the way forward. The Canon XL1 has a built in ND filter. Put it on and then open up the aperature really wide. Then use long lenses. Long lenses make the focus much more sensitive.
You might have to light the scene a bit more even though you've got your aperature wide open. You can also tweak the gain, but it's probably better to get it good without worrying about gain settings! :)

film8ker
03-28-2004, 07:00 AM
“There may be many reasons to use higher quality lenses, but increasing/decreasing DOF is not on of them”

While technically there are only two things that affect DOF (focal length and aperture), cheap lenses like those found on almost every pro-sumer camcorder have poor optics compared to more expensive lenses and this affects apparent DOF because they are not collimated to the precision that 16 or 35mm lenses. Since the optics are not as precise they appear to have a greater DOF because the overall image is not as sharp therefore the tolerances on the circle of confusion are less and a wider acceptable range appears to the CCD. Think of it like focusing the light of the sun through a magnifying glass. On a good one, you can get a very small circle with clearly defined edges before you start getting distortion in the shape and it starts to look like a figure 8. If you use a cheap plastic magnifying glass, it is very hard to get a clean circle, and the edges are not distinct even when the circle of light is relatively large. This isn’t a precise analogy but it’ll give you a good idea. Or, do an A/B comparison with a video lens and a film lens at the same focal length and f-stop on a Siemens Star and you’ll see a noticeable difference in picture clarity. This directly affects the apparent DOF, which is obvious when you think about it. If overall clarity is lost, then the delineation between the areas of soft focus and hard focus will be harder to determine.

NicklausLouis
03-28-2004, 10:50 AM
So to make the vid look more filmic, it is better to ...

a) move the camera foward and open wide to increase the DOF?

or

b) move the camera back and zoom in to decrease the DOF?

I've gotten so confused about all of it all of the sudden. Let's say I have an XL1 at my disposal, but I have no money to buy any new filters or lenses for the camera. What is the best way to make the video I shoot look more filmic?

Poke

NicklausLouis
03-28-2004, 11:20 PM
Are you trying to Poke fun at me? :wink:

Not at all ...

I am merely trying to "cut through the muck". I've heard so many different answers to this question that my head has begun to spin. I once thought I knew the answer, now I'm not so sure.

You answer was not confusing. You said move forward and open up. Simple.

Poke

Shaw
03-31-2004, 08:58 PM
Very interesting. Thanks for the summary iJack; it was quite helpful.

film8ker
04-03-2004, 08:19 AM
Yeah, exactly. Don’t forget though that zooming into a subject changes the relationship of how it looks compared to the background. For instance, if you have a subject standing in front of a building that’s far behind him/her with a wide-angle lens, and the camera is placed far from the subject creating a wide shot, the windows and details will be relatively small and the building will look distant. If you move the camera towards the subject to change the shot from a wide to a CU, then the building retains the characteristics of the small windows and perceived distance. However if you zoom into a subject to achieve a close-up, the background details will also enlarge relative to their original relationship to the subject, essentially making the building appear closer to the subject than it actually is.