Focus Issue

[Guest Tim]

I was using a borrowed DVX100a the other day ran into a bit of a focussing issue.

 

I was shooting a head-n-shoulders interview in low light, wide open (f1.7), manual focus. Camera locked off on sticks. No ND. Probably about 7 or 8 feet from the subject.

 

I'd zoom in all the way and set the focus, and then zoom out to the middle of the zoom to a good head and shoulders shot. Things looked sharp in the LCD, but when reviewing the footage later on a larger monitor, the wider shot was a little soft, and the background behind the subject was sharp.

 

Back in the office, I setup the DVX100a (f1.7) on sticks and pointed it at a large bookcase on the opposite wall. I set the Auto Focus to ON and watched the "focus numbers" in the LCD fluctuate consistently between 55 (wide-to-medium focal length) and 68 (zoomed in).

 

Is this a back focus problem?

[Alvin Pingol]

I'd zoom in all the way and set the focus, and then zoom out to the middle of the zoom to a good head and shoulders shot. Things looked sharp in the LCD, but when reviewing the footage later on a larger monitor, the wider shot was a little soft, and the background behind the subject was sharp.

 

I believe this technique does not work for this camera. Have you seen the DVX Focus Charts?

[J. Lamar King IMPOSTOR]

Make sure you check your camera against that chart. I know of at least two DVX's that do not focus anyhere near what that chart says.

[Greg Gross]

Tim, what do you mean by low light? Auto focus can be a problem

in low light! Was the area behind the subject lighter than the subject?

Was your subject maybe backlighted? Something threw your focus

off! The DX100A I would think would perform flawlessly except for the

known limitations of auto focus. I'm not sure I understand your situation.

I wonder if subject was backlit and you did not compensate with DX100A

"backlight" control(compensation). I wonder if you were shooting at known

limitations. With PD-170 I would have shot in manual mode(set my zoom)

manually. If Iwould have seen backlit situation I would have pressed the

"backlight" compensation control. I wonder if there was more light behind

your subject thus subject slightly out of focus,with more light behind sub-

subject rear of subject would focus sharply. I'm not sure if I'm interpeting

your situation accurately. I find that I have to be very careful in low light

during weddings in churches and when I shoot at the Pennsylvania State

Capitol in low light. Why did'nt you move your subject to more light for the

interview(I'm not trying to be a smart ---) always analyze your shoots,

shooting. I wonder maybe if you were shooting at limitations of auto focus

and also may have needed exposure compensation for backlight. My girl-

friend Stephanie, shoots with DX100A(loves it!). I'll pick her brain about you're

situation and get back to you here. Maybe something with f 1.7 too!

[Bob Hayes]

Thanks for the focus chart info. It has been dead on. I?m still pretty good at guessing distances and knowing 66% on the focus chart equals 6? etc.. Makes it pretty easy. It?s a shame the Auto focus is so slow on the camera.

 

Bob

[Tim Tyler]

Thanks for the focus chart info. 

 

Anybody have a chart they could upload here?

 

The old links are broken.

[Stas Tagios]

Here's the chart info, which I saved from the linked webpage before it was taken down:

 

Measured from the accessory shoe / light mount.

 

50% 3?10"

51% 3?11"

52% 4?

53% 4?1"

54% 4?2.5"

55% 4?4"

56% 4?5"

57% 4?6.5"

58% 4?8"

59% 4?10"

60% 4?11.5"

61% 5?

62% 5?2"

63% 5?4"

64% 5?6"

65% 5?9.5 ?

66% 6?

67% 6?3"

68% 6?6"

69% 6?9"

70% 7?

71% 7?4"

72% 7?8"

73% 8?

74% 8?6"

75% 8?12"

76% 9?6"

77% 10?

78% 10?8"

79% 11?6"

80% 12?4"

81% 13?4"

82% 14?7"

83% 16?

84% 17?9"

85% 19?11"

86% 22?9"

87% 26?6"

88% 31?10"

89% 39?9"

90% 52?11"

91% 79?5"

92% 160?8"

93% Infinity

[Tim Tyler]

Thanks!