HVX & HD100 - Differences and how to overcome it.

.. i went off on this subject yesterday. i dont know why.. just started typing and couldnt stop.

http://www.dvxuser.com/V3/showpost.php?p=212085&postcount=60

but it basically explains that DOF from imager size does NOt change.. but given the practicality factor.. is affected indirectly through having to change the FOV to maintain the same framing. it also covers focal point distance and the apparent DOF resulting which also comes into play.
 
redindian said:
I just cannot understand how the DOF will be same - maybe after i do a test, i can agree with you guys :)
Click to expand...

Would the depth of field change if the couple simply stepped backwards so as to be in the entire frame?

No. Their position in the field would change, but the depth of field of the focal length does not.

When you move the camera back, it's physically identical and indistinguishable from have the couple move.
 
There is only one point of focus in a picture - infront/behind of this point is depth of field

Depth of field is affected camera to subject distance (also with aperture+FL). The closer the subject the smaller the depth of field, and vice-versa

So would u not re-focus to account for the change in subject/camera position, hence what was in-focus before will move into circle of confusion.

as wells said, maybe we have the teriminology mixedup - I am sure everybody is right :)
 
Hey thanks for bringing up the little page that I did. I almost forgot I had that little illustration.
Yes, redindian, you would refocus the camera, but I still don't see the point. a 50mm lens on the JVC will be the same as a 50mm lens on the HVX. the Dof will be exactly the same. Now, the benifit that you would get is that you can use a 200 or 600mm lens on the JVC (if you wanted) and get very shallow Dof, however, you would have to be shooting from 100yds away! The point is, it doesn't matter what lens you use, the 1/3 in ccd is the limiting factor in how wide your field of view is. so while you may be using a 200mm lens, you will get the same Dof as a 200mm lens on a 35mm camera, but your field of view will be greatly condensed.
This for some reason seams to be a very difficult to understand subject, and I think it is because people get "FIELD OF VIEW" and "DEPTH OF FIELD" mixed up. They are related to eachother in that that coexist, but they are completly different things.
The misconception of the mini 35 is that it does not give you a shallower DEPTH OF FIELD but it gives you a wider FIELD OF VIEW. Adding a 35mm lens on a 1/3" ccd camera will give you the DEPTH OF FIELD of the lens, but it will limit your FIELD OF VIEW. I hope that makes more sense.
 
When you move the camera back, it's physically identical and indistinguishable from have the couple move.
Click to expand...

Right, but if they move, then you have to change the plane you're focusing to, and distance to subject *is* part of the whole DOF calculation.

Okay, here's the deal: as a technical matter, depth of field does not change based on image size. I mean, the whole notion is silly -- depth of field is a property of the lens, not of what the lens is projecting onto.

However, as a practical matter, smaller imagers will always exhibit deeper depth of field than larger imagers. The reason is because with a smaller imager, you require wider focal length lenses in order to deliver comparable fields of view, and the wider lenses are what create the deeper depth of field look.

Now, back to the mm-is-a-mm argument -- yes, exactly right. Take, for example, a Canon XL2. Its maximum telephoto is about 105mm. If you removed the video lens, and attached an EOS adapter and a 105mm EOS lens, you would get *exactly* the same field of view, and *exactly* the same depth of field, as if you were still using the video lens. A millimeter is a millimeter.

Now, if you put that 105mm EOS lens on an EOS camera, you would have a *wildly* different (and much wider) field of view. As long as you stayed at the same distance to the subject, you would have the same depth of field, but a much different field of view. And if you wanted to make the same field of view, you'd have to march the EOS camera much, much closer to the subject. When you do, THAT's when you change the depth of field.

DOF is determined by three stats: aperture, focal length, and distance to subject. A given lens at a given mm setting will deliver identical DOF if all those three elements are the same. But when you start talking about different imager sizes, you never keep all three elements the same. Typically, with a smaller sensor, you either get way further back, or use a shorter focal length -- and either (or both) techniques will cause deeper DOF.
 
It's like taking a picture with a 100mm lens on a 35mm still camera and printing a 4x6 of it.

Then, you take a pair of scissors and cut the edges of the print off so it's only a 1x1.5 print.
That's like what a 1/3" CCD would capture from the same lens.

But, you see, depth of field didn't change. Only angular field of view changed. Get it!?
 
scharky said:
Now, the benifit that you would get is that you can use a 200 or 600mm lens on the JVC (if you wanted) and get very shallow Dof, however, you would have to be shooting from 100yds away! .
Click to expand...

yes - u have to move waay back...but u will have a shallow DOF & a very narrow field of view.... in a JVC you CAN fit a real super-astro-telephoto 50mm lens :)

I havent worked with adapters, so are you saying attaching a 3x on a fixed HVX is the same ?


maybe time to hijak my own thread :)
here are few i shot with 'extenders' to get very very shallow DOF

12578109-M.jpg

12578108-M.jpg

12578111-M.jpg


maybe somebody can answer the rest of the points in page1
 
redindian,
You could take those same pictures with the same lenses on the JVC. What would look different
is you would only see 1/7.2 of the center of the frame. Does this make sense yet?

Cut the edges of those stills off in Photoshop to see what I mean.
 
yes - your statement is right - I understand where we mixed up. I wanted to keep the image same, you wanted to chop it off.

"DOF doesnt change" - thisiswells

"DOF changes if u want to keep your subject same"- me
 
In summary, your pictures would look the same when using a mini35 as those lenses on
a motion picture Super35mm camera (yes, they're using a full aperture gate in mini35)
 
yeah.. i think the part your missing redindian, i that a different field of view doe not make a different DOF.. its the same. the illustration picture you posted above shows this. the feild of view is how much you can see.. how wide or narrow the angle of vision is. but just because you can see more or less of an image. it doesnt chnage what the image is.. just like in the picture.. the different sensors see different amounts of the exact same image.


.. and if you back up .. you feild of view is till the same.. you still have the same angle of visiion.. lets say its 15 degrees.. if you move the camera back and dont touch anythiing.. you still only see 15 degrees in your FOV.. you just brought what you wanted to see into that 15 degrees is all. but the apparent DOF will change when you change your focal point distance to refocus on the subject further away. DOF is not actually directly linked to feild of view at all. the DOF only changes when you change the focal distance.







on a side techy head interesting note thats interesting to know..(well at least for me): technically, DOF is also NOT affected whatsoever by focal length.
yes .. i did just say that.

heres the deal. we all know that focal length affects apparent DOF which is all that matters as far as the image is concerned. but does changing the focal length actually change the DOF(aka: the depth of the plane which is in focus) of the lense if given a constant focal distance?.. answer.. no.
all that chaging the focal length does is magnify the image and change your FOV. it doesnt actually change whats in the image. so basically the DOF is exactly the same at a focal length of 4mm as it is at 300 if given a constant focal distance/distance to subject.

you can test this by focusing on a subject at a short focal length with your dvx and getting a frame grab, and then only change the focal length/zoom in and get another grab. use a smaller subject with the background far enough away so when you zoom in you can see the apparent DOF change around the whole subject

the apparent DOF will be different in the initial shots.. which again.. we all know is all that we care about .. but if you take the same FOV shot section out of the short focal legth grab, and uprez it to the size of the other image, you will see that the area around the subject is just as out of focus as it is in the longer focal legth grab.. the problem is just that you cant see how out of focus it is until you zoom in and magnify the issue. so again you want to look at the zoomed in grab, and then cut out the same image from a smaller area of the wide image.. then uprezblow up the image part you cut out till its the same size as the zoomed in image.. youll see that loss of detail due to limited optics and resolution set aside, it is the same image. therefore focal length DOES NOT technically affect DOF.. only arpeture setting and focal point distance do. it sort of like looking at a pointialism painting from a distance .. it looks crisp and good.. as you get up closer you see its little dot making up the image. same with a blurry image.. it looks acceptably sharp from far away.

but for all practical purposes.. it affects apparent DOF .. so who cares. :)
 
IAL is correct; technically, focal length actually doesn't affect DOF. However, visually, it most certainly does. The narrower field of view of a telephoto lens will serve to magnify the background much more, which will exaggerate its out-of-focusness.

For example, these shots were taken at the same aperture. One was zoomed all the way out, the other was zoomed all the way in, and the camera moved to make sure that the subject size stayed the same. Clearly the telephoto shot looks like its background is more out of focus (even though they're equally out of focus, if you were to magnify the background in the wide-angle shot to be as big as the background in the telephoto shot, it'd be the same!)
DOF-Combined.jpg


So when you're shooting, zoom all the way in and open the iris all the way open, and you'll get the shallowest DOF you can get (optically). Or, get as absolutely close as you possibly can (like in Redindian's shots) and open the iris up, and that can give you very shallow DOF.
 
Wow! Finally someone said it!

It is "perceived" DoF that changes with focal length. I think we had this argument on here a looong time ago.

Aaron
 
Barry_Green said:
DOF is determined by three stats: aperture, focal length, and distance to subject. A given lens at a given mm setting will deliver identical DOF if all those three elements are the same. But when you start talking about different imager sizes, you never keep all three elements the same. Typically, with a smaller sensor, you either get way further back, or use a shorter focal length -- and either (or both) techniques will cause deeper DOF.
Click to expand...

It's splitting hairs, but the DOF does not change when the subject moves. The DOF settings which produce the image you want may, but the DOF itself does not. If you have an adjustable flashlight set to beam useable light 100 feet in front of you, and something you want to see is 115 feet in front of you, you can get closer and illuminate that something. But you didn't change the range of the light. You changed the conditions of the environment.

EDIT: Gosh, this train left the station without me . . .
 
Okay, back to the original post...

Okay, back to the original post...

redindian said:
  1. How to achieve Varicam rates ?
    Do it in post production in a software. Surely not as good as the real one - but maybe we can live with it.​
  2. Slowmotion - How to record 720/60p
    Somehow record the 'Live output' to HDD. Barry says it is impractical for outdoor work as it takes a powerful comp + HD-SDI cards + RAID HDD + lots of space. So how to do slow-mo ? Using Software ?.​
Click to expand...


  1. Here's another option. The JVC has real-time 60P analog outputs. On the day you want to do slow-mo, rent a DVCPRO-HD deck (or something else capable of 720/60P) and plug it in. Instant 60fps.

    redindian said:
    [*]How to bypass GOP6 compression
    Dropouts might not be bad as we think and hopefully JVC did a better job than Sony. An expensive option is to record uncompressed to HDD.
    ​
    Click to expand...


    I've shot with the FX-1 and didn't notice serious dropouts at all.

    I hope Panasonic makes the HDX more practical for guys like me, but until the JVC or the Panasonic is in a store somewhere, I gotta use the Sony.

    So! I'm withholding judgement until these cameras actually hit the market and I can hold one in my hand. Who knows? Maybe Panasonic will figure out a way of recording DVCPRO-HD to cheap little DV tapes...​
 
..i think barrys illustration shold also help people understand why focus is so critical for the big screen. cause thiungs may look focused enough on a little monitor. but throw that same image ona 30 foot screen effectively magnifying it ..alot. and things which look to be in focus will soon reveal whether they actually are or not. thats why its important to know what your doing to get the best focus.. especially when working with optics like the anamorphic adaptor. barrys guide is reaaly helpful for giving you the methods to be sure your shots will hold up if you plan on going to the big screen.

this is why im particularily glad that the HVX will have a distance readout on the focus display. it gives you a sure fire way to check focus by distance to be sure in the HD world.. where the 3.5"inch lcd screen may not be doing the justice you want(even though it has focus peaking and zooming and all) to be sure beyond a shadow of a doubt and know your really nailing it. i normally eyball it, but when it has to be perfect.. this should provide a way to be airtight.
 
Where did you read that it's going to have a distance readout for focus? I've only heard that it will have ranged numbers like the DVX? I hope it has distance readouts.

Cheers
Aaron
 
id have to look waaay back in the HVX threads to find it.. but its there somewhere.. unless i just dreamed it up after a binge of cookies one night. :) check with barry green. im pretty sure he had mentioned it at some point.
 
Holy craparooni!

I remember something you posted Barry G about it only being a 0-99 readout (Don't know if you heard that from NAB or what) but obviously that's not the case now. Nice.


Now, that's got me wondering...I've no experience with lenses but I thought because it's not a proper manual focus with hard stops, that the focus readouts can only be relative, hence the 0-99 but being able to have a distance readout meant it had to be manual or something like that? Can someone clear this up for me?

Aza
 
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