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-   -   JVC GY-LS300 Depth Of Field Problem ? (https://www.dvinfo.net/forum/general-hd-720-1080-acquisition/528495-jvc-gy-ls300-depth-field-problem.html)

Scott Comeau May 22nd, 2015 04:52 PM

JVC GY-LS300 Depth Of Field Problem ?
 
I just bought the JVC GY-LS300 With the Samyang T1.5/85MM Lens

The Problem that I have is I can't seem the get everything in focus at the same time.

I can get foreground or the background in focus but not both at the same time.

I have the lens T-Stop at 5.6 and adjusting the focus ring to meet the distance that I shooting at.

I'm recording at 720P 60 FPS

Gain & WB are in Auto.

Any ideas ?

Thanks for any help you can give me !!

Scott

Jim Michael May 22nd, 2015 05:17 PM

Re: JVC GY-LS300 Depth Of Field Problem ?
 
Hi Scott,

Depth of field decreases with increased magnification, everything else being equal. An 85 for that sensor size will have a shallower depth of field than a shorter lens. That's one of the things that makes it a great focal length for portraits, the isolation of the subject from the background. Given a particular focal length and focus distance, you control depth of focus using the aperture. That has its limits as you'll start seeing diffraction effects (softening of focus) as you close down your aperture. Only your testing can determine at what point the diffraction effect is too much. The usual technique for that focal length is to take advantage of the shallow focus to accentuate the most important feature of your subject.

There are some tools to help illustrate the effect such as Online Depth of Field Calculator

Chris Harding May 26th, 2015 07:34 PM

Re: JVC GY-LS300 Depth Of Field Problem ?
 
Hi Scott

As a practical test with a camera with a Super35 sensor and 85mm lens at F5.6 ...if you are 15' away from your subject and focus exactly on your subject you are in focus technically from 14' to 16' in other words 1' in front and 1' behind the subject (that a DOF of 2') so the background will be way out of focus in this case.

The only way you can make the depth of field bigger is to stop the lens down but you also need to be careful that you don't go too far ..probably F16 is about your limit. The simplest solution is to get yourself a wider lens which will give you a greater DOF .... As an example I use a 10-24mm zoom at F3.5 on my stedicam and I'm in focus at say 10' away from 2' right out to infinity so my background is also sharp.

Try a few combinations on the DOF calculator and find a lens that will give you focus to infinity at your normal shooting distance. You definitely need to be looking at a wider lens and work in closer if you want more depth of field

Chris


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