Pulling Focus issues

Ematic

Ematic

Active member
Hey,

Just saw The Dark Knight last, must say truly disappointed. But I must digress.

What I was really curious about was why they said it was difficult to pull focus on imax film? Was it because the film frame was bigger? Therefore needing a more open iris creating a shorter DOF?

The issue was apparent, at least on the imax version I saw. A lot of the Imax sequences had moments were the focus was soft and other times it was just off completely.

thanks,
 
What I was really curious about was why they said it was difficult to pull focus on imax film? Was it because the film frame was bigger? Therefore needing a more open iris creating a shorter DOF?
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The film frame size would not necessarily deal with exposure or needing a more open iris to get shallow dof... if anything the larger film frame needed a longer lens length to get the equivalent composition, therefore inherently decreasing depth of field.

Ematic said:
The issue was apparent, at least on the imax version I saw. A lot of the Imax sequences had moments were the focus was soft and other times it was just off completely.

thanks,
Click to expand...

Don't forget to thank the projectionist.

The last 2 out of 3 movies I've gone to see, I had to go ask the projectionist to check focus... so sad when theaters don't check focus or use less bright bulbs to save money... what a slap in the face to film makers.
 
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This is where Coc (Circle of Confusion) comes into great affect. The focus of a shot will appear different depending on the projected size of the print. Obviously an IMAX screen is the biggest of the big, and will display very clearly, every buzz of focus. However, if you were to compare these same focus issues to how they appear on a traditional cinema screen, they would seem much less obtrusive.

The reason focus is such an issue when dealing with 65mm is because of the negative size. Think of it like a video camera. A DVX100 has a 1/3" chip, making it very hard to achieve a shallow depth of field, where as shooting on a 2/3" chip camera like a CineAlta will yield a shallower depth of field at a shorter focal length because of the size of the sensor. It's the same for film. 8mm will naturally have a deeper DOF than 16mm, and in turn 65mm has a significantly reduced DOF when compared to 35.
 
I just saw the film (not so much dissapointed, just confused about what I just watched)

I also noticed the focus problem. Doing some AC stuff myself recently, I paid particular attention to it.

Good steadicam though :-D
 
It was intentional that the focus went soft. They wanted the scenes to feel more spontaneous.


Marco
 
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