How do I focus my DVX100B?

L

lsc9x

Member
Ok, before I get flamed on my post's title, I have to preface this question by stating that I'm not totally stupid. I know that the DVX100B camera has an auto-focus feature, and manual focus, etc. I might be missing a feature here or there that might be useful, so I'll keep an open mind here!

Having said that, I am totally new to video shooting, but I have read the DVX Book cover to cover twice, and have watched the DVX DVD and I have read a lot of online tips and tricks articles, but after shooting with the DVX100B a bit I am still without a "Method" of getting clear, focused shots. Frankly, what I have shot looks like crap, and I know it's not the gear.

I see other people's work on TV that are using this very same camera, and their work makes my amateur shooting look like there is something physically wrong with my camera. Obviously this means that the camera operator, aka ME, just doesn't know what the hell he is doing!

Any help would be appreciated!

Let's make a few assumptions first:

1) The LCD display on my camera isn't good for obtaining focus, and I don't have money to buy a 20" video monitor. I can only use the viewfinder to frame shots.
2) The only controls that work on my camera are the iris (fStop??), the zoom, and the shutter and I can only use manual settings. (If auto settings can help, fine, just factor them in)
3) I have a rough idea of how much light is falling on the scene (in Watts or Lumens). Let's assume I don't have a light meter and have to "guess" how much light there is.
4) I know the exact distance that my subject will be from the camera, even if they are in motion during the shot. (i.e. a range from the camera lens)
5) I have a 100' steel tape measure and know how to use it.

I'm not really looking for a "hard fast" rule here, but rather some kind of method, based in science, that will give me reasonable confidence that my shot is going to be in focus, even if I have to "blind shoot" the scene.

Maybe another way to put this: You have a DVX100 (a, or b) and you get great focused shots.

How do you do it???

I'm open to buying books or visiting websites that might help with this, of course. I did find a DVX focus chart online, but after reading about the impact that shutter speed and fStop settings can have on a shot, it seems a bit inadequate for real world shooting.

Thanks for any advice!
 
lsc9x said:
2) The only controls that work on my camera are the iris (fStop??), the zoom, and the shutter and I can only use manual settings. (If auto settings can help, fine, just factor them in)
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Just to be clear... are you saying the focus ring doesn't work? Without "focus control" working, I doubt you will have luck focusing...?


If you just forgot to mention it, someone has posted a chart (I remember from years ago) that relates the DVX's focus numbers to actual distances (in feet). That might help when you know your distance. But the DVX LCD and viewfinder are OK for judging focus. What is your process? Remember that your focal distance is constant as you zoom, so you will get best focus by always zooming in as far as possible to focus, then zooming out to frame the shot. If you're shooting events or something, zoom all the way in BEFORE the event while setting up, and figure out ranges to key parts of the area where you'll be shooting, and try to develop a sense of distance.

If you mean manually focusing on a changing scene while shooting... the only answer is practice. Both in general, to learn overall how to focus well and quickly, and in specific before each scene you shoot, to nail down the specifics of that scene. It's not something that's really learned quickly.
 
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Here's the chart (or A chart)... I'm not sure if it needs any updating for the "B"/// but you can check, and if necessary make a chart for the B yourself...

http://egpetersen.com/more/morestuff/dvx100focus.htm


I see that you maybe saw the chart... but you shouldn't disregard it as you've mentioned. Iris and shutter speed DO NOT affect focal distance. The iris can affect depth of field, which is how far things can be from the ideal focal distance and still seem in focus... but the ideal focal point remains the same. Shutter speed only affects sharpness/blurriness due to the amount of motion that takes place during the exposure time (both camera motion and subject motion)... that is, the longer the exposure, the more everything has a chance to move, and thus blur the image).
 
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Why does it focus infinity at 93%? I've discovered by trial and error for it to be so (actually I tend to land on 94% but I have a 100B so it's either because of that or my dodgy old eyes), but my logical brain wants it to be at 100%. I can't envisage a situation where I'd want to focus beyond infinity (is that even possible?) so why does it let me?
 
One of the great mysteries... keep in mind few cameras can shoot "beyond infinity", which is great for sci fi production! I think Panny added this feature specifically for use in filming the Toy Story series.
 
ullanta said:
One of the great mysteries... keep in mind few cameras can shoot "beyond infinity", which is great for sci fi production! I think Panny added this feature specifically for use in filming the Toy Story series.
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Hahaha! I suppose what I wrote does sound a bit daft! Apologies if it was a naive question, I'm new to this game, but does anyone have the answer to this? Or is it really just one of the great mysteries?

Thanks.
 
I'm not making fun of your question... I'm making fun of the focus range! I don't know why it goes beyond infinity... but it's sure caused me problems in many cases when I wanted to reliably hit infinity...
 
Thanks for Information and Tips!

Thanks for Information and Tips!

Thanks for the info. Helps a lot!

I also learned a few things yesterday, so I am posting this stuff here. This is really basic stuff, but it was new to me. Fortunately, I have a friend, who is a film photographer, and he broke out his Hasselblad "old school" film camera and showed me how the settings work. It was very educational.

1) fStop: I thought that "iris", "aperture" and "fStop" were 3 different settings. Now that I know they are the same damn thing, that eliminates a LOT of confusion. I was getting confused between fStop and zoom, incorrectly thinking that fStop was a distance setting instead of a light setting.

2) There is an inversely proportional relationship between fStop and shutter speed. The higher the fStop number, the less light gets into the camera so the slower the shutter speed is needed to make the same exposure, but increases the risk of blur.

3) The percentages on the DVX focus chart (great, by the way) are directly from the camera view screen. 37 or lower on the percentage are "macro" focus settings. It seems kind of silly to exclude 1-37 from the chart. I did find some additional info for distances under 50%:

1' 11.5" 37
2' 0.75" 38
2' 1.5" 39
2' 2.25" 40
2' 3.25" 41
2' 5.25" 42
2' 6.75" 43
2' 8.25" 44
2' 10.25" 45
3' 46
3' 2.25" 47
3' 4" 48
3' 6.75" 49

4) It's nice to know that zoom is basically a non-factor in focusing (outside of zooming in tight to focus). I was getting hugely confused by zoom vs. fStop, but now that I know that they don't have much to do with each other, that's good.

Since focus seems mainly to do with the subject's distance from the camera lens, I do have a couple more questions:

1) Seems like it would be very difficult to keep a subject in focus if you are moving/holding the camera while the subject approaches or moves away from the camera lens at close range, say 5-10 feet. Would you use auto focus for this kind of situation or both carry and manually focus the camera at the same time?

2) Light metering. Aside from focus, correct exposure seems to depend on fStop and shutter speed. I don't have a light meter (probably should) but are there any features that allow you to know if you are getting the right exposure for a clear image? I know about Zebra stripes on the high end, but a lot of my footage is coming out pretty dark. I did buy a lighting kit, so that might help.

Thanks again for the help!
 
lsc9x said:
1) Seems like it would be very difficult to keep a subject in focus if you are moving/holding the camera while the subject approaches or moves away from the camera lens at close range, say 5-10 feet.
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Not really "very difficult", but it does take some practice. Of course it also depends on the speed of the approaching object and the settings that affect depth of field.

Would you use auto focus for this kind of situation or both carry and manually focus the camera at the same time?
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If you shoot interlaced, you can give AF a try (do not expect miracles though). In progressive mode, it is more or less unusable, almost certainly for this situation - unless the object approaching is a snail or something like that.

Personally, I do not use AF on the DVX at all.

One universal advice if I may: take the camera out to the street, play around, experiment, get used to it.
 
lsc9x said:
1) Seems like it would be very difficult to keep a subject in focus if you are moving/holding the camera while the subject approaches or moves away from the camera lens at close range, say 5-10 feet. Would you use auto focus for this kind of situation or both carry and manually focus the camera at the same time?
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Hmmm... in this situation you can use AF, try to manually focus as you go (with a doco look, and after lots of practice), or you can do it the narrative film way... block everything, detrmine focus marks, and have a focus puller (or attempt to hit the focus marks yourself if it's real simple).

2) Light metering. Aside from focus, correct exposure seems to depend on fStop and shutter speed. I don't have a light meter (probably should) but are there any features that allow you to know if you are getting the right exposure for a clear image? I know about Zebra stripes on the high end, but a lot of my footage is coming out pretty dark. I did buy a lighting kit, so that might help.
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Many of us would argue that for video, the camera is a much more useful than any external meter. There are zebras, which you can set to different levels; the spot meter..... good monitoring is also important when possible. Also... too dark where? On computer screens, eg, video will look a lot dorker than on a tv, etc.
 
its sd, it shouldn't be to hard. Zoomin all the way preferably on something with grin or subjects face. Turn the focus wheel untill it looks sharp. turn it a little more until it starts to loos sharpness, then back off to the sharpest point again. all this can be done witht he viewfinder
 
Many thanks!

Many thanks!

I have played around with the camera some more and am starting to get the hang of focusing. I think the zoom all the way in, focus, adjust and back off is the best approach for now. I am studying DOF next and trying to wrap my brain around that one.

The next question I have has to do with 24pA and getting the clearest image with it. I'll look around for an answer to that and if I don't find one, I'll post a new thread.

Thanks again everyone!
 
Far away from object/zoomed out/more closed iris equals larger DOF. This means its easier to focus but you wont get that effect of having objects directly behind the subject blurred. If you want the subject in focus but everything in front and behind them blured you need to zoom in, get closer, open your iris as much as possible. Your DOF will get shorter and you will need to focus more accurately. (do i have the iris backwards...someone help me out here lol)
 
Richter Video Equipment said:
Far away from object/zoomed out/more closed iris equals larger DOF. This means its easier to focus but you wont get that effect of having objects directly behind the subject blurred. If you want the subject in focus but everything in front and behind them blured you need to zoom in, get closer, open your iris as much as possible. Your DOF will get shorter and you will need to focus more accurately. (do i have the iris backwards...someone help me out here lol)
Click to expand...

Finally! A DOF explanation in plain English. Thanks!
 
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