focusing on a 4K frame

[tj williams]

What happens when a lot of people who's experience is mostly 1/3" chips(which are low rez even when shooting through one of the zoom/screen/prime lens setups) together with a camera of amazing resolving power. (That 4K still allows you to zoom in on the lip hair of the model) Put some still camera lenses on the front and.....

PROBLEMS: here are some!

1. you tape the shot on an 85mm lens open at 2.8 the focus distance to the image plane is 4 feet.


PROBLEM: 1. You enter 4 feet on the lens but the marking is off. I have taped a number of cine lenses and it is suprising on really high end lenses how many times the distances are not the sharp point on looking at the maglite.
(should mention here on way to see focus is to take the top of the maglite and look at the tiny bulb)

PROBLEM 2: You enter 4 feet on the lens but the distance between the 3' and 5' marks on your still lens, totals about 3/8 of an inch. So you put it about half way in between and hope for the best. With 4K circle of confusion this may be a vain hope.

PROBLEM 3: Even though you looked at the image on the larger video village monitor and held everyone up to do it yourself, the later problem: With a 4K image to play with what director can resist the slow push in...Gosh you never would a seen it before but there it is focused more on the nose and not the eyes. in the closer image at the end of the Davinci zoom.

PROBLEM 4: this is one of the big reasons cine. lenses are rehoused so the thread of the focus mechanism is finer and the distance between the marks is greater. Also many cine lenses are larger diameter in the barrel for the same reason. ak Panavision Primos. but the 30' and the 60' are so close together.

PROBLEM 5: The assistant turned to the op and said did I get the focus. The op looking into the depths of the 720P screen which actually has quite a bit les resolution in this small size says.....ehhhhh whhh weeeellllllll nowww....

ANSWERS: The big answer from the RED guys here is exactly how will RED focus work to prevent focus disasters?

[Billy Summers]

With the amazing and revolutionary "Focus Assist" from RED?!!

[Finner]

PROBLEM: 1. You enter 4 feet on the lens but the marking is off. I have taped a number of cine lenses and it is suprising on really high end lenses how many times the distances are not the sharp point on looking at the maglite.
(should mention here on way to see focus is to take the top of the maglite and look at the tiny bulb)

ANSWERS: The big answer from the RED guys here is exactly how will RED focus work to prevent focus disasters?


I may have a possible answer to why you have found problem 1 before.

I was prepping at Panavision when I was a focus puller a few years ago. There were quite a few other AC's doing prep on other lanes. One AC kept complaining about how his lenses were off. The Panavision tech checked the lenses and when the tech brought the lenses back he said they were fine. The AC ran out his tape on a lens again and said well how do you explain this, the lenses are off. The tech suggested maybe his cloth tape was stretched. It was. In fact it got the attention of most of the other AC's there and we all began comparing our rambone tapes to a newer steel hard tape. Only one AC's cloth tape was not stretched out and it was fairly new.

As far as new 4k focusing?

I say find a good focus puller and cross your fingers. I think it will be a bit of a new learning curve.

[Jannard]

Pulling focus will be one of the big surprises to someone stepping up from a 1/3" sensor camera. Probably the biggest surprise. Graeme has devised a pretty terrific aid for focus. It will help a LOT.

Jim

[Jeff Kilgroe]

I can't wait to see what Graeme has devised for us all. But this is (and has been) my biggest concern with RED. Especially since I am coming primarily from a 1/3" CCD world and intend to primarily use my Nikkor lenses to start out. I've used a 35mm adapter with these lenses on the HVX200 and that has taught me a lot, but I know I'm stepping into a whole new world here. The 720p output when I shoot with the HVX or Varicam can be monitored on set at full resolution. ...Not so with 4K. So I'm expecting a big learning curve and I'm assuming that like anything else, I'll just have to do it a bunch of times to start getting it figured out. ...I'm glad I won't be burning up film while I learn. :)

And since the subject of stretching tape has come up, what tape is recommended? Sadly, I'm using hockey tape. I'm a hockey player and always have tons of it around in a couple different colors. It's durable and is easy to work with and I'm very well acquainted with how well it wears and how much it gives and stretches. But I'm always looking for better (or even the more accepted and proper) solutions.

[Dominic Jones]

And since the subject of stretching tape has come up, what tape is recommended? Sadly, I'm using hockey tape. I'm a hockey player and always have tons of it around in a couple different colors. It's durable and is easy to work with and I'm very well acquainted with how well it wears and how much it gives and stretches. But I'm always looking for better (or even the more accepted and proper) solutions.

Hey AV - you realise he's talking about a tape measure, yeah?? If so, how are you measuring with hockey tape?!

[Jeff Kilgroe]

Heh. Sorry, I guess I was a bit tired when I posted that... It makes sense now after re-reading it. :o I know that tape measures can stretch out too, but I don't think I've ever had the luxury of owning one long enough to experience that. I have a bit of an excavator background and the tape measure is that semi-often used tool that usually rattled around in the [junk] toolbox in the back of a pickup, usually covered in grease. When it was used, it more often than not ended up stolen (like any other construction site tools when you turn your back for 20 seconds) or buried in a trench, or in the fill somewhere, or it would get run over. So I'm used to buying the multi-packs of $4.99 tapes. Heh.

As for hockey tape... It just fills the role of gaffers tape around here, that's all. For some reason in my mind it processes as the ring of tape a lot of us low budget guys use on our cheap lenses/cameras to make focus marks or to serve other taping purposes. Actually, I've found the hockey tape to work better than any true "gaffers tape" that I've tried and some "gaffers tape" is nothing more than cheap hockey tape. Weird, I know.

[Steve Freebairn]

If everything works out and I actually get to own a Red, I plan on shooting windowed 2k until I figure out the 4k focusing.

[Graeme Nattress]

If you have identical lenses, it makes no matter at all for the size of the sensor for you accurately you can focus. It's all about the lens, it's focal length and it's f-stop. The light travelling from your object to the sensor has no idea ahead of time what size the sensor is!

Thought experiment: take an image on your DSLR. Now crop that image to represent the light a smaller sensor would have captured. Does the sharpness of focus or DOF change? No it doesn't.

If your lens is the same, shooting 2k cropped isn't going to help you at all.

Difference is, larger (ie wider) sensors encourage the use of longer lenses, which magnify the difference between in-focus and out of focus.

Indeed, shooting a larger sensor could be better (if the lens is the same) as you could shrink the image and still retain a high resolution image. The shrunk image will appear to be less out of focus.

That said, the focus assist, unique to RED, should help immensely.

Graeme

[Rob Lohman]

Graeme: when I read kinobairn's post about shooting windowed 2K I was assuming he would use a S16 lens with that.

[Greg Voevodsky]

Hi Graeme,

Will the focus assist be able to tell you which way to pull focus - either closer or farther - I hope?

If not, might there be a way of adding either a pointer <- -> arrow or something?

[Graeme Nattress]

Focus assist doesn't work like that I'm afraid. It does tell you what is in focus, what is out of focus and how sharp that focus is or isn't for the entire image. It will make total sense when you see it.

Graeme

[Greg Voevodsky]

That sounds great. I know if the nose is in focus that I need to head back to the eyes? Hey, are the eyes gonna turn red if they're in focus?

[Graeme Nattress]

No, we decided not to implement a "RED eye production" feature. If you want RED eyes, just don't let your talent sleep :-)

Graeme

[Blair S. Paulsen]

Like many other features of the RedOne it floors me that so few camera manufacturers have taken advantage of the wealth of processing power in modern electronics to provide better focus assist. In the prosumer world it was either auto focus, which is a pretty risky option when you are getting paid as a professional operator, or focusing by eye using a EVF or LCD that typically cannot be trusted when the DoF is shallow.

Tip of the hat to the Red Team and the group that originally met to set design goals, a user friendly and reliable focus assist is an invaluable feature.

[Johan Malmsten]

Hi, lurker here... been reading and weeping about the whole thing almost a year now. Reading the prophecies, and weeping... well... since I can't afford it.

Now, that takes care of the introductions...

Well, since I too are a user of those tiny sensors I expect quite some learning to do on the 35mm sized ones... I've dabbled with it on my old Konica FC1 and found that it was feeding me wrong distances for focusing... 2 meters was focused as 0,7... so I got mostly blurry images on my first couple of rolls. So I now I go at it photographing with only measured distances. Sometimes I get it right, sometimes not... So I wouldn't try followfocus as I am now ;)

Then, at our university we where given a project to film a music video with their "new" 1080i HD cameras. And I started to fiddle around there and found a neat little function called "expanded focus" that, when pressed, gave me on the lcd a digital zoom-in that showed me the center part of the HD-image on the SD lcd screen. A temp blowup one might say or grotesque overscanning, so that I could focus using the lcd display. Of course this zoomed picture went nowhere else than to the little lcd, so I could do this while the director and producer was talking about other stuff in picture and not disturb them by constant zoomins for focusing. No followfocus was available as the camera only sported the built in lens with servozoom and focus.

I've found this function on DSLR's too.

I therefore feel a little silly asking this but, with this monster of a camera, Is there anything stopping from implementing anything like this to temporarily overscan the 4k image on a 720/1080 screen, for focusing? Of course I see the problems of doing this for pure followfocus as it is still mostly by feel. But one could go through setting upp the focused parts with actors/standins with this as a complement to the good old tried and true focus measuring tapes... or am I, as we say, completely out bycycling. (man, that sounds strange in english...)

But for now I say like others... there probably is a reason for this measure-tape-tradition to have lasted for a houndred years already.

[sean90291]

Given how incredibly expensive it would be to buy a production monitor truly capable of revealing the focus of Red's 4K image, I wondered if a smaller, portable LCD TV would be a cheap fallback for an HD production monitor in conjunction with Red's onboard focus assist. I know it's not 100% of the 4K image. But at least 1080i would give some additional indication of focus. And the issues of precise colour won't really be that important for the monitor, since we'd probably be shooting RAW (compressed) and doing all the color balancing in RedCine anyhow. Would the cheaper LCD TV be a waste of cash for this purpose?

[Alex Fostvedt]

How about the dreaded "Circle of Confusion"? Also will DOF change with the different image sizes, ie. 4k-35mm DOF, 2k-S16mm DOF?

[tj williams]

Graeme: regarding your lens post: set up two reds. side by side, one with windowed 2k sensor one showing full sensor now zoom so the field of view is the same, (same objects at the edge of frame) set the iris the same.

this is two cameras making the same shot. The DOF in the windowed camera will be noticeably larger. Thus focusing for the same shot will be more easy. I think this is what Kinobairn was trying to say.

I gotta ask.

So GRaeme, tell me the amazing revolutionary magic read focuser doesnt involve zooming in the video in the VF or on the LCD screen!! how about infrared!

[S. Um]

Focus assist doesn't work like that I'm afraid. It does tell you what is in focus, what is out of focus and how sharp that focus is or isn't for the entire image. It will make total sense when you see it.

Graeme

Nice. Will you be able to use it while taping? Kind of like zebras but for focus?

[Graeme Nattress]

Yes, while recording.

Graeme

[S. Um]

Nice. Looking forward to seeing it.

Hope you guys have a patent, because everybody's going to want one.

[tj williams]

if the viewfinder sells for less than 3K you should put a Panasonic mount and cable on. You could sell a bunch more as it's seriously hard to focus with the Sony Panasonic HD viewfinders. Looking forward to seeing this solution at NAB