Depth of field on A1u?
 

Does anyone have an recommendations on this? I am looking for ideas on how to accurately get accurate DOF of a large croud from certain distances. There is no known F value setting so any help is appreciated.

DOF is a zone in front of and behind the exact focus point, that is *perceived* to be in focus to the human eye. In fact ONLY the focus point is in sharp focus, but due to the way optics work, objects closer to and further away from the camera can still look sharp and in-focus.
Most people think that the DOF is evenly distributed around the focus point (for example 10meters in-front of focus-point and 10metres behind the focus-point) but this isn't actually true - there will actually be 'more' DOF behind the focus-point than in front of it. So if you're focused on an object at, say, 30metres from the camera, the area considered to be in focus BEYOND that may be an additional 10metres, but the area considered to be in focus IN FRONT of that point may be just 5metres-ish.

I'm not aware of any easy way to measure/calculate the DOF at certain apertures. DOF is affected by the distance that the focus-point is away from the camera, and the focal-length of the lens used (i.e. wideangle - to - telephoto) and also the physical size of the sensor.
Also remember that the A1 has 2 or 3 ND filters that physically move into the optical path for light levels over a certain value (the PHYSICAL aperture leaves will stay at i think f4). ND filters will NOT affect the DOF, but physical aperture changes DO affect DOF. So even if you camera reported f5.6, chances are that the physical aperture is STILL at f4 but there's now part of an ND filter in the optical path and that's how the camera acheives a 'bogus' f5.6

To cut a long story short, the best way to judge DOF for an object that you want to appear to be fully in-focus is to look carefully through the viewfinder (higher resolution than the LCD screen on the A1) and use the expanded focus setting to check what you want is accpetably in focus.

IMO.

A couple of general notes though: set the exposure as high as possible (without clipping or getting seriously over-exposed) and zoom in as much as possible (before starting to shoot) to maximze DOF...
Play with it a bit until you get some settings that work dependably for you.

uhh, i think i've just entered the Twilight Zone...
Don't you mean zoom *out* as much as possible to maximise DOF?

Generally to maximise DOF for a certain camera:
- Select small aperture / iris on the lens (must be physical aperture! - see above)
- increase distance to subject
- use as wide-angle zoom setting as poss. (obviously within the constraints of getting the shot you want)

DOF is inherently pretty big on a camcorder with a 1/3in sensor. That's why it's hard to get that really nice very-shallow DOF that you can get on a film SLR or a digital SLR that uses a BIG sensor or even a full-sized 35mm sensor (very very expensive cams these are).

Technically there is no aperature setting on the A1 or atleast it does not show it. This was what my question was regarding. I understand, to a point, DOF from my DSLR days. I am trying to figure out the best settings on the A1 for this. Basically I will be shooting from around 20 feet and would like a large DOF to caputre a fairly big group. I imagine the more light I had the smaller the Aperature I could get, there by increasing my DOF. I will not have an extreme amount of light to work with which may be an issue.

Thanks

Stu:
As you increase the focal length (zoom) any background object in the out of focus area is magnified so you get more blur. Back the camera up away from the subject and zoom in with the iris wide open to get more DOF action.

Try it for yourself and then tell me if I'm wrong. :)

Michael:
There are aperture settings, they just aren't in the form of f-stops... Just bring up the Exposure to as high as you can get away in order to get the most DOF

I think there may be some confusion on here as far as terminology. What does "more" or "less" DOF mean to you? If you open the apeture wide and zoom in close, you will get the narrow depth of field seen in movies where the subject is in focus, but everything behind it is not. It helps to have the background as far away from the subject as possible. The smaller the apeture and the more wide angle you shoot, the DOF will become wider, making a wider range of distance appear to be in focus.

Exactly Evan. If a person wants to have that softness for items outside of focus (that you see in film), then they would need to zoom in. This is what most people are trying for I believe.

If, on the other hand, you want everything to be in focus then wide is definitely better...But usually the auto settings on the HC1/A1 will do pretty well give you a pretty wide DOF without help.

I think you got it Evan - definitely a terminology issue here, not a disagreement with the fundamentals.

My interpretation of what Frank said : "and zoom in as much as possible (before starting to shoot) to maximze DOF"
is that he meant you get MORE depth-of-field by zooming in and this isn't correct.
So it's a terminology thing : I think what Frank means by "DOF" is his wording for *shallow* depth-of-field, i.e. not much in focus in front of or behind the focus-point.

I've been using SLR's since the 1980's so i'm fully conversant with DOF issues and also studied quite a lot of optics - it's just frank's term for "DOF" isn't the same as mine! (or the vast majority of other people's either for that matter)

Having said that (previous post) i *am* going to disagree with this.

Exposure itself has nothing at all, inherently, to do with Depth-of-field (shallow or deep).
It's *aperture* that affects it (amongst other things), and i believe Frank's comment stems from the fact that most camcorders tend to hang onto their default shutter speed as long as they can. So by "giving it more exposure" (& assuming the shutter speed is constant and we leave gain out of the picture) then the aperture will be bigger, i.e. tending to max. aperture and this will give a shallow Depth-of-field.
If you fix shutter speed, and fix gain then, yes, in that sense an increased exposure will mean shallow DOF, but it's ONLY cause if shutter and gain are fixed then the only thing that can vary is aperture and that's what affects DOF.

Finally, you CAN see what aperture that the A1 has used for any footage.
Not *during* footage, but immediately after, replay the footage, with 'Data Code', 'camera data' enabled and it will give you shutter speed, aperture (as an f-stop), gain in dB, what white-balance was used, and also whether expsoure was automatic or manual.
So if you're unsure what aperture cam is using for a scene, shoot 5secs of that scene, quick review with data code on, and then you know.

Remember that above a certain brightness the camera will hang on to a physical aperture of f4 and throw in Neutral-Density filters to control light-levels to avoid nasty resolution-limiting diffraction effects.
Ultimately it WILL stop down the physical aperture more than f4 but this is in really extreme situation when even all the ND filters in the optical path aren't helping enough.

I definitely agree with you Stu that it is *aperture* that is really changed, but the place to change it on the HC1/A1 is in the Exposure part of the menu. So again we're really saying the same thing in different ways for the most part. I apologize for the confusion.

What I do personally is lock down the shutter speed to 60 (taking those variables out of the picture) and set the Exposure up to open the aperture more.

BTW - It has been mentioned that the Camera Data feedback may not be entirely accurate, which ticks some people off no end.

Ok. So basically I am looking at a dark picture to get the widest DOF possible? This is assuming I lock down to 1/60 SS.

So you DO want more depth. I'm so used to everybody wanting a shallower DOF so their output will look more like film. Heh.

I owe you a beer Stu!

Like most other things, it will be a tradeoff. The best picture will be come from lowering the exposure/aperture settings, but not going so low that it creates gain and noise and pulling the zoom out to the widest shot possible.

Have you thought of adding a wide angle lens? They aren't terribly expensive and it looks like you might find it useful..

Thanks guys...Frank...you are correct. For this event I need more depth and it will not be a very well lit area. I will experiment. I have the Sony wide angle sitting on my camera right now :-)

I believe that you are completetly right about this one. Video cameras, opposite of DSLR cameras, try to shoot at their default shutter speed (PAL - 50fps or 1/50, NTSC 60fps or 1/60) as long as possible. The only way to achieve this is by opening or closing down aparture. To prevent it from closing down to much, a ND filter can be used. Another way to get some control over the aparture is with the spot meter. I personally think it is one of the best ways to control exposure as you can use a 18% gray card as well as use natural/environment colors to get the correct parts of the image properly exposed. Although this does not answer the question asked here, it is a way to get the best exposure for your shots and by spot metering darker or lighter objects you can open or close down. The 18% gray card is your "0" point. But again, I think Stu got it right.

hej, here are some cheap findings in search for dof, only not with a1 :(

focus and stability are my problems

bothe are made with hdc-1, auto-mode except manual focus,


first video; both poor light and good light conditions, winter in sweden with letus lens-adaptor and canon fd 50mm f1.4 lens, .wmv 1500kb/s, 17mb. 1.38min.

http://www.streamload.com/xid/sweden_test.wmv


second video , my garden in amsterdam and neighbour-cat, medium light condition with
sony 0.6x wide-lens / close up first half manual focus, second half autofocus, .wmv hdv-stream, 99mb, 4.19min

http://www.streamload.com/xid/poes_hdv.wmv

Ooh dangerous thing to say Frank... i can never settle for just one !! ;-)

Floris - respect is due to you. Anyone who is aware of 18% gray cards and what they're for and how camera light meters are calibrated to assume the world is 18% gray (most of the time) gets my vote....

So when Frank buys me that beer, i'll make him buy me two, and i´ll give one to Floris !!

Hey now...I have to 18% gray cards ;-) Does make quite the difference IMHO Expecially in my Nikon D100 days

I suspect a plot to turn me into a poor and wretched drunk.

I'm down.

Joff, very nice videos. I am wondering if you could share some pictures of your camcorder with the lenses. I would love to be able to achieve similar results.

I am particular interested in the Sweden video you composed. Also, what filter did you use for the last shot with the women profiles? I really enjoyed the dramatic feel to it.

[/quCan you tell me something about this lens adapter? Where can I buy it and how does it work? Does it also work with Nikon objectives? Like Alex asked, do you have a picture with this adapter and lens attached to your HC1?

Any feedaback would be greatly appreciated!

Yes in my opinion a substantial amount of both videos, the subject is simply out of focus. The cat is sometimes in focus, sometimes out. The camera (when on autofocus) sometimes selected the background to focus on (this is common). Also at times, the cat is closer than the minimum focus-able distance. All these cams have a minimum focus distance. Telemacro would help a lot as this will let you focus really close.

The Sweden video - again, most of the time the women were just out of focus. In this instance, i'd auto focus as the camera should be able to hang onto that subject fine. Or, zoom in, autofocus, then flick to manual focus to hold it if you're concerned the cam will lose focus.

nice 'feel' to the vids nevertheless.

I personally find manual focus the most convenient to use but it will take some practices to apply it to moving subjects. But like Stu mentioned, I really like the feel of the Swedish footage. I guess it is related to the Canon lens.

Six stops from the right and aperture is max open. 1.8.

It *will* show it on playback.
In TAPE mode, select :
DATA CODE
then:
CAMERA DATA.

It will show tech info on replay on-screen including :
- aperture (f-stop)
- shutter-speed
- white-balance mode
- amount of gain dB
- whether camera was in Auto-exposure or Manual exposure mode.

Aperture will not get smaller (i.e. smaller physical aperture/iris, BIGGER f-stop number) than f4 on HC1 unless there's a LOT of light. It switches in internal ND filters instead as long as it can.

But Depth-of-field for these cams with small sensors is pretty good so i wouldn't worry too much.

Does anyone else have experience with 35mm lens adapters? The premise of those adapters looks promising. But as I have never worked with them, I do not know the advantages and disadvantages. I am also not sure if I want to spend like $300-600 on such a system and lenses.

I always heard the Sony data code isn't always accurate...

its accurate for shutterspeed and gain and exposure mode and whitebalance.
The only item that is of some debate, and this is anyway only on certain Sony cams is the reported aperture. But am pretty certain that this value is accurate on these cams we're referring to. You need to remember that the 'aperture' beyond f4 is most of the time controlled by inline ND filters and therefore its no longer a genuine physical aperture change.

All other items, an most likely aperture too, are accurate, and are useful in reviewing footage.

Of course, if the chart at http://hdvforever.com/hdv/exposure/ is accurate, the system of using f-stops is seriously curtailed as the aperture settings available are: 8, 6.8, 5.6, 4.8 and then 4, which is where you start getting the ND filters jumping into play.

Dof
 

Hi,

I have been experimenting with my HC1 modes and find that the 'Portrait' mode can be used to reduce DOF. I suspect it simply opens up the Iris to the lowest 'F' value allowed for the given lighting conditions. Conversely there is a 'Landscape' mode that may work to increase DOF although I have not tested this. I have a Canon SLR and it has similiar functions. For the HC1 it is explained on page 44 of the user manual.

[For shallow DOF: In brighter light I would add a couple of ND filters onto the front. I have found the optimum background blur to be achieved by zooming in at least half way on the slider -and ideally as much as possible- and placing the subject 1/3 distance to background...]

Finally, here is an online DOF calculator to have a play with:

http://www.dofmaster.com/dofjs.html


Regards, Nick.

You are correct on both modes. Landscape and nighttime also focus basically on infinity so do not use them for anything close up.

setup adapter
 

here some photo's of the letus-adapter on the hc1


http://www.streamload.com/xid/RIMG0001s.JPG

http://www.streamload.com/xid/RIMG0006s.JPG

http://www.streamload.com/xid/RIMG0008s.JPG

Cool kit
 

Wow! That IS a cool piece of kit. I have heard of people making home-brew adapters but this looks good and for $300 !! Where's my cheque book!!!

I would be interested to see the results you are getting with this -even some still frames would be great/adequate.

Also, you lose what, 1.5 stops of light? Have you found it an issue?

What lenses are you using on the front? (Do you use a prime / zoom or can you use the camera zoom?)

Sorry, many questions, v. excited!

It looks very nice. There are two setups: the normal one and the flip version. With the normal version, you need to flip the image in post, with the flip version, your image is flipped for you so your viewfinder and lcd have a normal image. You lose around 1,5 stops of light, depending on the lens you use.

You cannot use the camera zoom as you are zooming/focussing on a groundglass image so your camera focus/zoom needs to stay put. You focus/zoom with the 35mm lens. You can however change the aparture with the camera and the lens, but the lens will be the most convenient.

I do not own this lens, but this is what I was told.

Which lenses
 

Oh I forgot to ask: which type/make of lenses can you fit?

(I have a range of Canon SLR lenses, that would be ideal...hopes for good news!)

Opening the iris to let in more light gives the image a more shallow depth of field.

heath