AC90: Focus matters

[dee123]

So far, i'm still working on getting the right color for my AC90. For now i still prefer the warmer colors of my handypanny HDC SD700. But in post lots can be done.

Not for focus though. And it does trouble me.
1) Can anyone tell me why we don't get a true distance on the screen? I really prefer something i can relate to (eg metres!). Does the camera not know?
2) Does the focus change when zooming in and out? (seems like it, the digit is changing..)
3) Why is the focus assist so inaccurate? It shows too much as "in focus" i think.
4) Why is normal or push-auto focus so nervous? The value sometimes varies 60 'points', or whatever i should call the units. It takes quite long for it to settle on some value.

As a suggested feature (who knows a firmware update): priority for near focus. As in almost any case (at least any auto-focus case) you would want to have the foreground in focus and the background maybe blurry. If the cam checks a few points in the image and sets focus on the nearest one this would be fantastic, especially for interviews where (rule of thirds) the subject is not in the center. Alternatively touch focus would be nice as well.

I would like the camera better if the focus would be handled more straightforward. (for instance like my old Canon XH-A1)

Having said this, many other things i do like about the cam..
David

 

[dee123]

i was hoping someone had some ideas on this.
but i just saw barry's book is available to order so i hope to find out more in there.

no one interested in 'near focus priority' or, even more simple, face recognition -only- for focus? (in manual mode?)

d.

 

[ChrisHarding]

Hi David

The AC-130 is also the same. Remember that the camera needs to focus on something and if you have a cluttered foreground it can even choose multiple items. Then again also remember with tiny 1/4.7" chips unless you are really close your depth of field is HUGE so if the camera is "running" from 60 to 80 all points are well inside the depth of field anyway!!
I only had HMC80's and AC-130's not the AC-90 ..does it have expanded focus or focus peaking like the 130??...I found that using auto focus and then switching to manual once the display stops running is a good way to get in the ball park, then simply get it spot on with the focus wheel and expanded focus if you have it. Touch to spot focus is absolutely brilliant but sadly I think only Sony's have it... I use it all the time on tripod mounted cams on my Sony EA-50's .... I used the focus display that runs from 00-99 for years and you get used to it!! If you are standing behind the tripod you can only really estimate a distance so it makes no difference if the camera says "76" or 5.6 metres as you can only roughly judge 5.6 metres anyway unless you get a laser measurer! You will soon get to know that people standing in front of you are "66" counts away so you know the camera is pretty close...after that trust your eyes and any focus assist functions on the camera.

 

[dee123]

hi,

thanks for your reply. the ag-ac90 has 'macro focus' but the manual does not clear up what it is, or what the consequences are. i do notice it switches a lot between normal and macro mode.
what i do a lot is interview people, but changing the frame quite often, either by moving or zooming. especially in that range (say between 1 and 3 metres) the AC90 is quite nervous in focussing. also the subject moves from the center (when it's near) to just off the center (firther away, it moves to a third of the left or right side). especially in badly lit circumstances the cam can't decide what to do when i move.

face recognition would be a briliant feature, when it does it just for focus. i don't want the cam to interfere with the other settings that it does in 'auto', the only mode that uses face recognition now.
such a shame, the technique is available, but it is just doing too much. i wish this could be changed with a firmware upgrade, it would be awesome.

as for the sony's, nice they have the touch focus, but i really like the ac90's 50fps. this quickly became a 'must' for me.

d

 

[ChrisHarding]

Hi David

Most AF systems use contrast focussing and Panny do as well so in really low light when there is poor contrast, the AF will struggle with any camera. It's just something most cam owners have to live with so you need to supply more light or focus manually ..that's the bottom line. Yean double frame rate is neat ..I use mine however mainly if I know I'm going to do slomo sequences at weddings. My HMC80's also showed focus "running" but always was in focus regardless. I did find the the AC-130 used to get totally confused with focussing on lots of people (like on a dance floor) and that used to go crazy ..however by all accounts the 90 is way better and focus is supposed to be a lot better. Low light and moving subjects will fool most cameras not just the AC-90!!!

Chris

 

[steve4505]

hi,

thanks for your reply. the ag-ac90 has 'macro focus' but the manual does not clear up what it is, or what the consequences are. i do notice it switches a lot between normal and macro mode.

I can't answer this question for sure, but from what I saw on tests of the 160 there was a distinct change at a certain distance (like only about a foot) where the camera went into "macro" mode. https://vimeo.com/34816634 In the comments they say macro mode is up to 6 feet away (like you are running into at 1+ meters) for the AG160, but I personally am not finding this issue on the AG90. They suggest just moving back a couple of feet.

I have not been having a problem focusing unless I am outdoors and the sunlight is causing visibility issues. Its really hard to set focus on quickly moving targets too (unless they are at infinity M95) if you have it on fully manual. For instance I was outdoors in my back yard and a vulture flew (was circling) right over my head. I needed to hit the focus button (to quickly switch to auto) and that may have given me a chance to get focus before it flew away in a few seconds. I tried to focus manually and since this camera goes past infinity (doesn't stop) I failed the shot. Very likely if I had hit the right button I could have gotten auto to work well enough. I wasn't wanting to switch to IA because I was shooting 60fps and I didn't want it to mess with my shutter speed, etc. I goofed the shot up anyways (when it was really close to me) because I zoomed in too far and couldn't follow it. Being unable to follow would have messed the the auto focus probably too because It may have been at like A85 because it was so close and then as i missed it for a few frames I might have gone to A95 and back and forth. I would have just loved to see what it would do and not me being the one making the failed shot!

I would tend to avoid the auto focus because I found it wants to change more than it needs to and that is more noticeable than someone going slightly soft on a zoom. I tried in on an professional interview gig with a group of folk and the jumping around was enough to realize I am not going to do that again. Barry suggests z99, open iris, then manual focus using the focus assist. Zoom out to what you where you want to be and your focus should still be perfect. You can double check using the digital zoom, but remember to get it back to off before recording. Its funny because that's what I used to always do on the much more expensive production cameras and its the same here. Though at times the back focus would get messed up and we would have to reset that (this camera doesn't have a back-focus adjustment).

Off subject a bit but Barry said the minimum focus distance is 3.5cm/1-3/8". I measured my lens hood and its close to 4.4cm/1-3/4" In tests I was removing my lens hood to get close enough at Z67 and M00 and getting this "magical" macro close-up ability of this camera.