Jump to content


Photo

problem with focus in tight closeup


  • Please log in to reply
8 replies to this topic

#1 Ruby Gold

Ruby Gold
  • Basic Members
  • PipPip
  • 34 posts
  • Producer

Posted 08 July 2006 - 05:05 PM

One other question. After looking at footage I shot in a recent interview, I noticed that when I went in for a very tight close-up, the shot was slightly out of focus.

I was in 60i mode, using 3 point lighting, manual white balance, manual iris setting, and manual focus.

To set focus, I framed my shot, noting the zoom number, then zoomed all the way in and focused. During the interview I wd zoom in or out for a tighter or wider shot, going out as wide as the original zoom number I noted. Everything seems in focus except the super tight close-ups.

Any ideas why these were out of focus or how to correct for that in the future wd be greatly appreciated. Thanks.

Ruby
  • 0

#2 Stephen Williams

Stephen Williams
  • Sustaining Members
  • 4708 posts
  • Cinematographer
  • Europe

Posted 09 July 2006 - 03:51 AM

One other question. After looking at footage I shot in a recent interview, I noticed that when I went in for a very tight close-up, the shot was slightly out of focus.

I was in 60i mode, using 3 point lighting, manual white balance, manual iris setting, and manual focus.

To set focus, I framed my shot, noting the zoom number, then zoomed all the way in and focused. During the interview I wd zoom in or out for a tighter or wider shot, going out as wide as the original zoom number I noted. Everything seems in focus except the super tight close-ups.

Any ideas why these were out of focus or how to correct for that in the future wd be greatly appreciated. Thanks.

Ruby



Hi,

The persons head may have moved slightly! Always check and recheck the focus on close ups. You may well have to pull focus during the shot as well.

Stephen
  • 0

#3 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19759 posts
  • Cinematographer
  • Los Angeles

Posted 09 July 2006 - 12:03 PM

Focus is just more critical in a tight shot, so you were off. This is the main reason why focus pullers are used in filmmaking, to follow moving people in tight shots...
  • 0

#4 Bob Hayes

Bob Hayes
  • Basic Members
  • PipPipPipPip
  • 1087 posts
  • Cinematographer
  • Culver City, California

Posted 09 July 2006 - 12:08 PM

People move. On interviews I get in the habit of zooming in a checking focus occasionally when there is a break in the questions or when the interviewer asks a long question. This works if the camera tracks properly when focusing and zooming in and I think the VX 100A does.
  • 0

#5 Peter J DeCrescenzo

Peter J DeCrescenzo
  • Sustaining Members
  • 620 posts
  • Camera Operator
  • Portland, OR, USA www.peterdv.com Blog: http://herefortheweather.wordpress.com/

Posted 09 July 2006 - 02:18 PM

In addition to the excellent suggestions and comments here, in case you had the lens' iris wide open (smallest f-stop value), you might test using a more closed-down iris, such as f4 or f5.6. A larger value f-stop will make the depth of field less shallow, increasing the depth of the scene which will appear in focus.

Of course, increasing the f-stop value also affects exposure, so an iris adjustment might not be appropriate depending on your lighting resources and so forth. And for some shots you may want the DOF as shallow as possible.

Note that as you stop-down the iris (increase the f-stop value) on a 1/3" CCD cam's built-in lens (such as the DVX100), light diffraction/scattering through a very small iris may increase to the point of causing undesireable softening of the image. This is usually not an issue with f-stop values of approx. f5.6 or smaller on these cams. You can double-check for this on a high resolution video monitor.
  • 0

#6 Ruby Gold

Ruby Gold
  • Basic Members
  • PipPip
  • 34 posts
  • Producer

Posted 09 July 2006 - 03:39 PM

Thanks to all for great tips--I really appreciate it. And Peter, I had the exposure at f/6.8 most of the time, f/5.6 for a few clips. It doesn't seem from what you said that those stops wd have impacted the focus. But, I guess, as many suggested, that the movement of the subject may have been the issue.

As for a monitor--any suggestions on what to get that wd be useful but not cost an arm and leg (I spent my arms and legs on the camers), and also how to calibrate said monitor?

Thanks again-
Ruby

In addition to the excellent suggestions and comments here, in case you had the lens' iris wide open (smallest f-stop value), you might test using a more closed-down iris, such as f4 or f5.6. A larger value f-stop will make the depth of field less shallow, increasing the depth of the scene which will appear in focus.

Of course, increasing the f-stop value also affects exposure, so an iris adjustment might not be appropriate depending on your lighting resources and so forth. And for some shots you may want the DOF as shallow as possible.

Note that as you stop-down the iris (increase the f-stop value) on a 1/3" CCD cam's built-in lens (such as the DVX100), light diffraction/scattering through a very small iris may increase to the point of causing undesireable softening of the image. This is usually not an issue with f-stop values of approx. f5.6 or smaller on these cams. You can double-check for this on a high resolution video monitor.


  • 0

#7 Peter J DeCrescenzo

Peter J DeCrescenzo
  • Sustaining Members
  • 620 posts
  • Camera Operator
  • Portland, OR, USA www.peterdv.com Blog: http://herefortheweather.wordpress.com/

Posted 09 July 2006 - 03:58 PM

... how to calibrate said monitor?

http://videouniversity.com/tvbars2.htm
  • 0

#8 Peter J DeCrescenzo

Peter J DeCrescenzo
  • Sustaining Members
  • 620 posts
  • Camera Operator
  • Portland, OR, USA www.peterdv.com Blog: http://herefortheweather.wordpress.com/

Posted 09 July 2006 - 04:28 PM

... As for a monitor--any suggestions on what to get that wd be useful but not cost an arm and leg ...

Examples of relatively low-cost JVC CRT-type monitors:
http://www.bhphotovi...egoryNavigation
http://www.bhphotovi...egoryNavigation

Examples of relatively low-cost Sony CRT-type monitors:
http://www.bhphotovi...egoryNavigation
http://www.bhphotovi...egoryNavigation

Sony also makes a variety of CRT monitors which are higher resolution and more color-accurate than those listed above, but they cost more, too. Ikegami-branded monitors can sometimes be a good value also.

Sony, Marshall, JVC and others also sell many different model LCD monitors.

CRT monitors tend to be more accurate than LCDs for displaying exposure and color. CRTs typically have superior ability to display a wide angle-of-view, fast response time (low lag/blur), and are better at displaying interlaced video, especially standard definition interlaced video.

Although LCDs are getting better all the time, typically only the most expensive LCDs come close to performing as well in these regards compared to CRTs. In their favor, LCDs are generally much thinner, lighter and use less power compared to CRTs. Since LCDs are inherently progressive devices, they can display progressive video more accurately and less expensively compared to CRTs.

For environmental reasons manufacture of CRT monitors is being phased-out, because CRT monitors contain a large amount of lead. Some dealers are selling the last remaining stocks of certain CRT models.
  • 0

#9 Ruby Gold

Ruby Gold
  • Basic Members
  • PipPip
  • 34 posts
  • Producer

Posted 09 July 2006 - 07:06 PM

Thanks again Peter for all the helpful info.
Ruby
  • 0


rebotnix Technologies

Ritter Battery

Metropolis Post

The Slider

Rig Wheels Passport

Media Blackout - Custom Cables and AKS

Wooden Camera

FJS International, LLC

Opal

Aerial Filmworks

Tai Audio

CineTape

Paralinx LLC

Technodolly

Abel Cine

Glidecam

CineLab

Gamma Ray Digital Inc

Willys Widgets

Visual Products

Broadcast Solutions Inc

Rig Wheels Passport

Gamma Ray Digital Inc

Broadcast Solutions Inc

Wooden Camera

Abel Cine

Metropolis Post

rebotnix Technologies

CineLab

Visual Products

Aerial Filmworks

Media Blackout - Custom Cables and AKS

The Slider

Tai Audio

FJS International, LLC

Paralinx LLC

Willys Widgets

Technodolly

Opal

CineTape

Glidecam

Ritter Battery