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Tips for getting sharp focus?


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#1 Jason Hinkle (RIP)

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Posted 04 September 2008 - 05:58 PM

I was wondering if someone could help me with some tips for getting a really crisp, sharp focus on 16mm film? I know there are a lot of variables and I've already discovered some things, but I would like to hear any tricks or tips out there.

During the shoot I am really anal about zooming in and getting a super sharp focus on the subject, yet some shots still come out looking soft & amateurish. The one thing I have managed to figure out on my own is that shooting with the aperture wide open seems to make it difficult and/or impossible for me to get a really sharp focus. Adding more light so that I can close it down even 1 f-stop seems to make a big difference. I am almost thinking that my lens will simply not capture a sharp image with the f-stop wide open. Could that be right?

Obviously the glass is critical, but I have gotten some very sharp shots so I know my equipment is capable of producing great images. I would just like to be able to do it consistently. I have a few lenses but for the purposes of this question, you could just assume I'm using the old standard Angenioux 12-120.

Thanks for any advice.
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#2 Allen Achterberg

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Posted 04 September 2008 - 06:59 PM

The Ang 12-120 isnt the sharpest of Lenses to begin with. Check your lens against a star pattern focus chart to make sure that the witness marks match up. zooming in and getting critical focus is hardly ever necessary assuming your witness marks are lining up. I would stop down and shoot at a T4, maybe a 5.6 with that lens. Measure out your distance and set the lens accordingly, zooming in and then back out sometimes you may accidently bump the focus ring. you are best of using your own eye focus to determine sharpest settings. Film stock, is it old? new? that effects image sharpenss too. pay attention and make sure after you have your distance set on the lens that neither you or your subject change in distance from each other.

maybe you could post some frame grabs?
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#3 Ira Ratner

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Posted 04 September 2008 - 07:33 PM

Jason, you understand the concept of depth of field, right? If not, let us know.

Depending on the amount of light and the film you're using...which affects your correct aperture/F stop...that will have a huge impact on any focusing problems.
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#4 Jason Hinkle (RIP)

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Posted 04 September 2008 - 09:18 PM

maybe you could post some frame grabs?


Thanks Allen. Here's some footage I just got back. I picked these two because they are almost an identical setup - the main difference being the first image f-stop was closed 2 stops and the 2nd image was wide open. In both shots the camera is about 12 feet away from the subject with nearly identical amount of lighting. This is filmed on brand new Vision3 stock under daylight balanced cool lights with an 85 filter. The 2nd shot is not just one bad take either - everything from that setup is soft, including some long and medium shots. The f-stop seems to be responsible, however I don't have enough experience to feel 100% confident saying that ;-)

The first shot is about as sharp as I seem to be able to get. I wouldn't mind getting even sharper, but I'm not sure reg 16mm best light transfer to MiniDV is going to get much sharper..? Maybe it's time for better lenses? I want to make sure I'm getting the best I can from my gear though.

Posted Image

Posted Image

Thanks again so much for your help.

Edited by Jason Hinkle, 04 September 2008 - 09:19 PM.

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#5 Jason Hinkle (RIP)

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Posted 04 September 2008 - 09:36 PM

Jason, you understand the concept of depth of field, right? If not, let us know.

Depending on the amount of light and the film you're using...which affects your correct aperture/F stop...that will have a huge impact on any focusing problems.


Thanks Ira, I do understand the wider f-stop is going to be more shallow depth of field which would theoretically make it less forgiving to focus. But I'm pretty darn sure that I had crisp focus in the viewfinder. I had about 80 ft candles of light according to the meter, with the 85 filter I should have closed it one stop. That was actually an oversight on my part leaving it open in this setup, but as it turns out it clued me in to the fact that the wide-open shots were all a bit soft.

If it's just lack of skill, I'm definitely ready to accept that too. But, I suspect this lens isn't good wide open - I've seen a lot of similar 16mm results on YouTube - it seems like so much footage comes out soft. I want to learn how to get those crisp images I see you guys here posting!
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#6 Allen Achterberg

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Posted 04 September 2008 - 09:50 PM

The 2nd one is pretty soft. What camera were you using? what Lens mount? is there any sort of adapter on the lens to adapt it to your camera? Im not implying that this is the problem, however knowing the details of that may open up some possibilities.

I mean look at the Blue halo you got goin on there in the 2nd photo. the aberration seems to be non existent in the first photo. What condition is that lens in? It looks pretty poor in optical performance. is it pretty dirty inside? dusty? stopping down makes a stronger beam of light which can hide dusty class somewhat, but the more you open the softer light beam is weakend and sharpness is lost. this looks like a possibility.
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#7 Jason Hinkle (RIP)

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Posted 05 September 2008 - 12:01 AM

The 2nd one is pretty soft. What camera were you using? what Lens mount? ...


Thanks again Allen, that actually makes a lot of sense about the wide lens softening the light and, perhaps flaws in the lens are amplified. You're right about the blue halo too - it's even worse in some other shots from that same setup. The lens looks clean to me, but then I don't know for sure if I would recognize a bad lens. I don't see any obvious dirt or fog on the glass. The weird thing is that both shots are the same camera, lens, same film stock, lights and everything. It's an Eclair ACL with the Angie 12-120 Camflex mount.

Probably doing some tests like you mentioned is the best way to know for sure what's going on?
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#8 Andrew Koch

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Posted 05 September 2008 - 03:19 AM

Have you had the collimation checked? If the lens is not properly collimated for your camera, your images will not be as sharp. This is more noticeable using wider lenses and less noticeable on longer lenses. If this is off, it could be sharp in the eyepiece, but soft on the film. Stopping down the lens also helps make this problem less noticeable. Take the camera to a rental house and ask them if they wouldn't mind checking it for you.
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#9 Jason Hinkle (RIP)

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Posted 05 September 2008 - 06:08 PM

Take the camera to a rental house and ask them if they wouldn't mind checking it for you.


Thanks Andrew, I'm going to do that.
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