Tele-converter/Telephoto

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Just a quick question: does the tele-converter/telephoto lens attachment (like the one from century optics) decrease your depth of field, or does the depth of field only appear to be less because of some kind of zoom distortion?
 
Re: Tele-converter/Telephoto

That's a fascinating question.  The answer is, technically, strictly speaking, depth of field truly has nothing to do with focal length, it is strictly a function of aperture and distance to subject.

The APPEARANCE of shallow DOF has *everything* to do with focal length, however, specifically because of the so-called effect of "zoom distortion" -- telephoto lenses optically compress a scene, bringing the background closer in appearance, in effect magnifying the background.  And while the background may be equally sharp in telephoto or wide-angle lens shots, when you magnify it, it becomes blurry.

So, if you want to get technical, technically it is not due to a change in actual focus, but it is due to the magnification of the background (and, concurrently, wide-angle lenses seem to have deeper DOF because they "push the background away", which makes it smaller, which makes it look sharper).

But in reality, all you need to know is, the more telephoto you have, the more it'll seem like the background is out of focus.
 
Re: Tele-converter/Telephoto

[quote author=Barry_Green link=board=Links;num=1083965212;start=0#1 date=05/07/04 at 14:30:38]That's a fascinating question.  The answer is, technically, strictly speaking, depth of field truly has nothing to do with focal length, it is strictly a function of aperture and distance to subject.

The APPEARANCE of shallow DOF has *everything* to do with focal length, however, specifically because of the so-called effect of "zoom distortion" -- telephoto lenses optically compress a scene, bringing the background closer in appearance, in effect magnifying the background.  And while the background may be equally sharp in telephoto or wide-angle lens shots, when you magnify it, it becomes blurry.

So, if you want to get technical, technically it is not due to a change in actual focus, but it is due to the magnification of the background (and, concurrently, wide-angle lenses seem to have deeper DOF because they "push the background away", which makes it smaller, which makes it look sharper).

But in reality, all you need to know is, the more telephoto you have, the more it'll seem like the background is out of focus.[/quote]

Interesting. So visually, does having actual shallow depth of field (say, from a 35mm camera lens) and having the so called "pseudo" depth of field (from a telephoto lens) produce the same sort of image? If so, I might strongly consider buying the telephoto lens from century optics. Another thing though... are there any obvious or apparent drawbacks to the telephoto lens?
 
Re: Tele-converter/Telephoto

Just a note: I'm asking because getting 24 fps and the appearance of "shallow depth of field" are what I'm looking for, which is why I'm looking into the dvx100a and any possible lens attachments that can help me achieve this effect.
 
Re: Tele-converter/Telephoto

Hey Nguyen,

So visually, does having actual shallow depth of field (say, from a 35mm camera lens) and having the so called "pseudo" depth of field (from a telephoto lens) produce the same sort of image?
Click to expand...

Sort of. If you can move the distance of the two objects (the one in the foreground and the one in the background) far enough apart, then yes, you can have the same result. If you can't move the objects further apart, then visually the tele converter will make the background look extra big and close, kind of different from the effect of shallow focus you can get with a 35mm cam.

But don't let this discourage you. People have found ways to get results by placing cameras down halls and moving chairs to the middle of rooms, separating the forground from the background. The thing is, the 10x on the camera can already allow you to do quite a bit of this for shallow focus. I don't think a tele converter is going to help much. It'll just make you have to move things even further apart for an even more difficult to acheive effect. I'd say try it a bit more the 10x before buying the tele for this purpose.
 
Re: Tele-converter/Telephoto

[quote author=Everdene link=board=Links;num=1083965212;start=0#4 date=05/07/04 at 15:00:22]Hey Nguyen,


Sort of. If you can move the distance of the two objects (the one in the foreground and the one in the background) far enough apart, then yes, you can have the same result. If you can't move the objects further apart, then visually the tele converter will make the background look extra big and close, kind of different from the effect of shallow focus you can get with a 35mm cam.

But don't let this discourage you. People have found ways to get results by placing cameras down halls and moving chairs to the middle of rooms, separating the forground from the background. The thing is, the 10x on the camera can already allow you to do quite a bit of this for shallow focus. I don't think a tele converter is going to help much. It'll just make you have to move things even further apart for an even more difficult to acheive effect. I'd say try it a bit more the 10x before buying the tele for this purpose.[/quote]

One thing I've been hearing about the dvx100(a) is the 10x lens being a liability. Why is 10x so bad? Is 10x really much worse than, say, a 16x lens, for achieving this simulated "depth of field" effect? By the way, thanks for the quick responses.
 
Re: Tele-converter/Telephoto

[quote author=Nguyen D. Nguyen link=board=Links;num=1083965212;start=0#2 date=05/07/04 at 14:45:44]

So visually, does having actual shallow depth of field (say, from a 35mm camera lens) and having the so called "pseudo" depth of field (from a telephoto lens) produce the same sort of image?
[/quote]
Yes, because it's the same thing -- all lenses exhibit the same depth of field characteristics, whether they're on a video camera or a movie camera or a 35mm still camera or whatever.  The difference is in the focal length.  Think about it: the DVX has a 4.5-45mm lens, which they say is "equivalent to 32.5-325mm on a 35mm camera".  Which do you think will deliver shallower DOF: 45mm, or 325mm?

The effect you'd get with the teleconverter (which boosts the focal length from 45mm up to 72mm) is the same you'd get if the DVX had a 72mm lens in the first place.  There's nothing "fake" about it.  But it'll never approach what you could get with a wider field of view like on a 35mm still camera, where you can legitimately use a 300mm lens.

are there any obvious or apparent drawbacks to the telephoto lens?
Click to expand...
Several drawbacks: first, it's about $800.  Second, it limits your zoom range to being only about the upper 40% or so.  Third, it's huge and heavy.

And, the telephoto effect is rather mild, at only 1.6x magnification.  If it was 2x or 3x, then it'd be enough to make a significant difference.  But at 1.6x, it's not really strong enough to justify the extra $800 or so, in my opinion.

There are ways to get shallower DOF looks with the stock camera, but you can only do so much with a 45mm lens.  There's only so shallow that you can get.  You can "cheat" in two ways however: you can use the mini35, which lets you attach cine lenses and lets you put on 100mm, 200mm, 300mm lenses and get super-shallow DOF... or you could put a SoftScreen (http://www.indietoolbox.com) behind your subject, which will give you the lush shallow DOF look you're looking for (but primarily only on head shots).
 
Re: Tele-converter/Telephoto

[quote author=Nguyen D. Nguyen link=board=Links;num=1083965212;start=0#5 date=05/07/04 at 15:10:11]

One thing I've been hearing about the dvx100(a) is the 10x lens being a liability. Why is 10x so bad? Is 10x really much worse than, say, a 16x lens, for achieving this simulated "depth of field" effect? [/quote]

The more telephoto your lens is, the blurrier the background can look.

The DVX has a maximum telephoto of 45mm. It's kind of hard to get shallow DOF out of a 45mm lens.

The PD150 has a 72mm maximum telephoto. The XL1 with 16x lens has a maximum telephoto of 88mm. It's obviously easier to get shallow backgrounds with an 88mm lens than it is with a 45mm lens.
 
Re: Tele-converter/Telephoto

Thanks for all the information. Maybe I'll think about getting the mce quickstream thing instead. But none of you wouldn't happen to have any side by side comparisons of with/without telephoto lens trying to achieve shallow depth of field, would you?
 
Re: Tele-converter/Telephoto

[quote author=Nguyen D. Nguyen link=board=Links;num=1083965212;start=0#8 date=05/07/04 at 15:26:22]Thanks for all the information. Maybe I'll think about getting the mce quickstream thing instead. But none of you wouldn't happen to have any side by side comparisons of with/without telephoto lens trying to achieve shallow depth of field, would you?[/quote]

What I meant it, is there ENOUGH of a difference between the kind of shallow depth of field effect between the stock dvx100a lens and one with a 1.6x century optics telephoto/teleconverter attached?
 
Re: Tele-converter/Telephoto

Under the right circumstances, when you can frame the shot properly, there will be a noticeable difference.  $800 worth?  That's a question only you could answer.  You could try it out with your SLR though -- compose a shot with a 45mm lens, then move to where you frame the same shot with a 75mm lens (or use 50mm and 80mm, whatever you've got) and note the difference.  If the difference you see would be worth $800 to you, then spring for it.

Or, not to continually keep pimping this product (especially since I sold the product line and don't get a dime from it, but it still works) you could use the SoftScreen, which will get you the shallow-DOF look you want regardless of what lens you're using. Here's a picture with the same framing with/without the SoftScreen:

SSOutdoor.jpg

www.SoftScreen.us
 
Re: Tele-converter/Telephoto

[quote author=Barry_Green link=board=Links;num=1083965212;start=0#10 date=05/08/04 at 10:42:21]Under the right circumstances, when you can frame the shot properly, there will be a noticeable difference.  $800 worth?  That's a question only you could answer.  You could try it out with your SLR though -- compose a shot with a 45mm lens, then move to where you frame the same shot with a 75mm lens (or use 50mm and 80mm, whatever you've got) and note the difference.  If the difference you see would be worth $800 to you, then spring for it.

Or, not to continually keep pimping this product (especially since I sold the product line and don't get a dime from it, but it still works) you could use the SoftScreen, which will get you the shallow-DOF look you want regardless of what lens you're using.  Here's a picture with the same framing with/without the SoftScreen:

SSOutdoor.jpg

www.SoftScreen.us[/quote]

Barry,

I took a look at that softscreen product yesterday. Very nice actually, considering how moderately more "difficult" the alternatives to getting the same shot are. Problem is, the screen is only so big. And you're right, 800 dollars is a bit steep for something that only gives a max of 72mm. I'll mostly be filming in doors, so there isn't that much space to "move back" in order to get that shallow depth of focus effect.

I just ordered the dvx100a today through b&hphoto, so maybe just to start off, I'll use the stock lens. Of course, we'd all like to have the p+s technik, but 7600$ for the base unit and 2300$ for the panasonic adapter (not to mention lens price) is for people who have money to burn. Do you know of any techniques that can be used to simulate shallow depth of field, without the softscreen or the p+s technik adapter? (move back? zoom out? change iris settings?)
 
Re: Tele-converter/Telephoto

http://www.dvxuser.com/cgi-bin/DVX/YaBB.cgi?board=news;action=display;num=1083366247

Please understand, you're basically asking for "something for nothing". The very reason products like the mini35 and the SoftScreen were developed is because it's extremely difficult to get that shallow-focus look with the lenses that these cameras have. So the thread above details the process you'd use to get as shallow as you can, but it's nothing like as shallow as you could get with the mini35 or SS.
 
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