Back Focus Problem

Marcus Marchesseault · June 14th, 2007, 02:49 AM

Piotr, I should have said "AF assist". I think I need to go out and practice with the AF assist before I am comfortable changing my methods. I don't want to be one of those curmudgeons that is inflexible in the way things are done, but I am also nervous about trusting the camera with focus unless I don't have any choice in the matter.

Piotr Wozniacki · June 14th, 2007, 03:15 AM

Markus, I myself only recently discovered that the AF assist function works so well. I didn't trust it before, but must admit the more I use the V1, the more capable and forgiving I find it. In fact, the auto functions work so well, that - after the initial fascination with full manual mode - I find myself more and more tending towards using them, and only revert to manual when really needed.

So my usual method of shooting with the V1 would be to set the shutter speed manually, switch to auto exposure as it can prompt me to engage ND1 or ND2 if needed with the current lighting conditions and the iris limit set to 5.6 in the menu, and only return to manual exposure if some special circumstancies (like backlit object for instance) require it.

Similarly, I always start with AF on; if there is no risk of AF hunting (usually low light can cause it), I keep it that way, and use the ring to freely change the distance/object I want the AF to set to (using LOW peaking intensity, see below). Only when the object I need to stay in perfect focus does not have features that AF relies on, or it's not bright enough - I switch to manual focus (and crank up the peaking intensity - see below).

I have developed my own way to ensure that a subject's features are good enough to trust the AF will find it and stick to it, while I'm still at control of where the object actually is: always use the lowest possible peaking intensity. With normal outdoors lighting conditions, I always set the peaking intensity to LOW. This way, only "true" sharp edges do peak. Of course, the lower lighting, the higher peaking intensity is appropriate.

Lee Berger · June 14th, 2007, 04:42 PM

I appreciate everyone's response into my post. I didn't mean to cause any alarm or insinuate that this is a widespread issue with the V1. That fact that no one else on this forum has reported this issue is a good sign.

My camera arrived at Sony's repair center in New Jersey yesterday and I'll be sure to post the details when I get it back (including how quickly Sony turns it around). Also I totally agree with the idea that once framing is set you can always tweak the focus either manually or via the auto focus. A problematic back focus is not a show stopper if you're aware of it. Most of all I wanted the issue taken care of while still under warranty.

Cheers,

Lee

Stephen Armour · June 15th, 2007, 10:58 AM

Quote:

Originally Posted by Steve Mullen

Bob nailed it 100%.
...I spent 4 months testing the AF -- and even at scenes that needed +9dB gain, it was very hard to fake it out.

PS 1: there is actually a problem with zooming in to get focus. When you zoom in really tight on a face -- there are no hard edges to focus on. The AF and Focus Assist fail. (I think this may be way some feel they need a field monitor.) It's better to zoom in on the upper torso so arms and belt are in the frame. Remember, if you don't plan to zoom in further, the focus is fine.

PS2: Up to about Z60 -- the DOF is so great you almost don't need to worry about focus. That's why AF works so well. It doesn't have very much to do. :)

Steve, aren't extreme closes on any faces almost always "eye focus" shots, or did I teach my cameramen wrong? It's the highlight and iris edge that make it easier. The angle for upper body and belt can change radically depending on where and how you're shooting, so we shoot for the eyes. Low angle focus on upper body can put eyes out of focus and that's where our eyes naturally look.

With our little 7" Marshall or the 8" SWIT, these shots are no-brainers, but using the V-1's LCD, we almost always use the focus assist and have few probs. The eyes have it.

Lee Berger · June 18th, 2007, 02:00 PM

A technician from Sony called today and informed me that there was nothing wrong with the BF. He explained that the problem occurred because the Macro setting was ON. For a moment I felt stupid and then I remembered that I suspected Macro and checked the manual. On pg. 64 it says:
"Since the default setting is [ON] you can focus a subject within 80cm...."

"If the default setting is Macro ON then it has to be a back focus issue," I reasoned at the time. There was nothing about Back Focus.

If Macro adversely affects back focus then the default should be Macro OFF. Or at least there should be something about it in the manual. I was fooled in part because I'm used to cameras with interchangeable lenses where it's obvious when Macro in ON.

Of course I still feel kind of dumb in that I should have double checked with the Macro set to OFF before I sent it back to Sony. Live and learn.

By the way, they got to it quickly as it was received on Wednesday and off the bench by Saturday.

Seth Bloombaum · June 18th, 2007, 02:31 PM

Lee, sorry for your pain on this. I really appreciate your posting the solution. In fact, I have an interview that is soft - I usually leave Macro "off" on general principles, I wonder if I left it on for that interview.

VERY interesting info that the Macro setting invalidates some usual applications of manual focus (zoom in, focus, zoom out to your shot).

June 14th, 2007, 03:15 AM	#17
Piotr Wozniacki Inner Circle Join Date: Aug 2006 Location: Poland Posts: 4,086	Markus, I myself only recently discovered that the AF assist function works so well. I didn't trust it before, but must admit the more I use the V1, the more capable and forgiving I find it. In fact, the auto functions work so well, that - after the initial fascination with full manual mode - I find myself more and more tending towards using them, and only revert to manual when really needed. So my usual method of shooting with the V1 would be to set the shutter speed manually, switch to auto exposure as it can prompt me to engage ND1 or ND2 if needed with the current lighting conditions and the iris limit set to 5.6 in the menu, and only return to manual exposure if some special circumstancies (like backlit object for instance) require it. Similarly, I always start with AF on; if there is no risk of AF hunting (usually low light can cause it), I keep it that way, and use the ring to freely change the distance/object I want the AF to set to (using LOW peaking intensity, see below). Only when the object I need to stay in perfect focus does not have features that AF relies on, or it's not bright enough - I switch to manual focus (and crank up the peaking intensity - see below). I have developed my own way to ensure that a subject's features are good enough to trust the AF will find it and stick to it, while I'm still at control of where the object actually is: always use the lowest possible peaking intensity. With normal outdoors lighting conditions, I always set the peaking intensity to LOW. This way, only "true" sharp edges do peak. Of course, the lower lighting, the higher peaking intensity is appropriate. __________________ Sony PXW-FS7 \| DaVinci Resolve Studio; Magix Vegas Pro; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; Decklink 4K Extreme 12G; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive Last edited by Piotr Wozniacki; June 14th, 2007 at 04:59 AM.

June 18th, 2007, 02:00 PM	#20
Lee Berger Major Player Join Date: Dec 2006 Location: Tallahassee, Florida Posts: 326	Back Focus Issue Resolved A technician from Sony called today and informed me that there was nothing wrong with the BF. He explained that the problem occurred because the Macro setting was ON. For a moment I felt stupid and then I remembered that I suspected Macro and checked the manual. On pg. 64 it says: "Since the default setting is [ON] you can focus a subject within 80cm...." "If the default setting is Macro ON then it has to be a back focus issue," I reasoned at the time. There was nothing about Back Focus. If Macro adversely affects back focus then the default should be Macro OFF. Or at least there should be something about it in the manual. I was fooled in part because I'm used to cameras with interchangeable lenses where it's obvious when Macro in ON. Of course I still feel kind of dumb in that I should have double checked with the Macro set to OFF before I sent it back to Sony. Live and learn. By the way, they got to it quickly as it was received on Wednesday and off the bench by Saturday.

June 14th, 2007, 02:49 AM	#16
Marcus Marchesseault Trustee Join Date: Nov 2005 Location: Honolulu, HI Posts: 1,961	Piotr, I should have said "AF assist". I think I need to go out and practice with the AF assist before I am comfortable changing my methods. I don't want to be one of those curmudgeons that is inflexible in the way things are done, but I am also nervous about trusting the camera with focus unless I don't have any choice in the matter.

June 14th, 2007, 04:42 PM	#18
Lee Berger Major Player Join Date: Dec 2006 Location: Tallahassee, Florida Posts: 326	I appreciate everyone's response into my post. I didn't mean to cause any alarm or insinuate that this is a widespread issue with the V1. That fact that no one else on this forum has reported this issue is a good sign. My camera arrived at Sony's repair center in New Jersey yesterday and I'll be sure to post the details when I get it back (including how quickly Sony turns it around). Also I totally agree with the idea that once framing is set you can always tweak the focus either manually or via the auto focus. A problematic back focus is not a show stopper if you're aware of it. Most of all I wanted the issue taken care of while still under warranty. Cheers, Lee

June 18th, 2007, 02:31 PM	#21
Seth Bloombaum Inner Circle Join Date: Sep 2003 Location: Portland, Oregon Posts: 3,420	Lee, sorry for your pain on this. I really appreciate your posting the solution. In fact, I have an interview that is soft - I usually leave Macro "off" on general principles, I wonder if I left it on for that interview. VERY interesting info that the Macro setting invalidates some usual applications of manual focus (zoom in, focus, zoom out to your shot).