NEED HELP: Measures of lens element. 2.40  AS

M

MrFloppy

Member
Hi friends,

I need to get a bit of help from yours.

I'll be buying a new DVX100AE in a month, and need to get a anamorphic aspect ratio with it. I've found a anamorphic adaptor that provides a 2 to 1 anamorphosis (2.40 to 1) and has a 67 mm filter thread, which is smaller than DVX100 (72mm, correct me if I'm wrong), but it is my hope to get it adapted with a middle ring.

In order to calculate vignetting, I need to know the dimension (in milimeters, if possible) of the front square lens element, I mean, that little glass square in the front of the lens.

Could any of yours post here these measures?

If what I'm trying works, I could provide you guys with a solution to get full resolution Cinemascope images with your dvx100 under 300usd.

Cheers,

Jose
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

A few things of note with your method. Most anamorphic lenses will display some kind of vignetting at full wide. If you are using a lens with a smaller thread than the built in lens, you are doubling or even tripling this problem.

1. You need to zoom in to compensate for regular vignetting (at full wide, it tends to be rampant in these kind of lenses).
2. You will need to zoom in again to compensate for the smaller thread size.
3. You will need to zoom in again to compensate for the step down ring.

After all this compensation, you won't need to worry about the size of the lens element in the camera because you'll be way past that in zoom alone.

You are also going to need more light for your shots because you are going to lose a couple of stops due to the zoom factor.

If you can live with these limitations (more like a regular prime lens in terms of its limited focal range), then I think it will work.
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

Well, it'll sort of work -- you'll end up with a vignetted 2.66:1 image, which will be severely squeezed in the viewfinder and nearly impossible to properly compose for the aspect ratio. People complain about the 1.33 squeeze factor of the Panasonic anamorphic... trying to compose with a 3x stronger squeeze will be quite difficult.

And then, what will you do with the image? If you're planning on making a film print, you'll have to chop off image from the sides, which will result in a resolution loss. If you're planning on making an anamorphic DVD you'll have to unsqueeze it in post to 16:9, which will result in a 33% resolution loss.

I mean, good luck with your experiment and all, I'm just wondering what your goals are and if it makes sense through the whole production chain...
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

Because you'd be losing resolution regardless with a 2:1 squeeze, it would probably be better (and more convenient) to just letterbox for 2.40 in the first place...you'll be losing resolution, yes, but you'd do that with the 2:1 lens as well, *and* this won't cause as many headaches...
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

Mike_Donis:

Where's the resolution loss?. You only loss resolution if you crop the image (up to 276 pixels, about 230 lines), but using an anamorphic adaptor allows you to compress full 600 lines of resolution (no cropping) in a shorter image, that increases also perceived sharpness.

When printing to 35mm, you directly print the anamorphosed image to get a cinemascope print, and using dvx100 full resolutive power. Cropping reduces image resolution, and reduces also sharpness because image must be cropped and stretched to get a anamorphic print.

Jose
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

The thing is, you're losing resolution when getting a 2.40:1 image from a 2:1 anamorphic lens...

With 35mm, the negative area used in anamorphic photography comes to about 1.2:1, NOT 4:3. The entire 35mm frame is 4:3, yes, but due to the optical soundtrack on the film, space is lost on the sides...the fact that nobody uses the crappy quality audio track is irrelevant; we still chop it off, so that when we stretch the width of the frame by 2, as with a 2:1 lens, we get approximately 2.40:1.

Using that same lens, with DV, as Barry has already mentioned, gets you a 2.66:1 image, NOT a 2.40:1 image. So in order to get a 2.40 frame, you'd need to actually crop the sides of the image (Barry already discussed this). So because you're throwing away resolution in order to get 2.40 anyways, why not save the trouble of anamorphic in the first place.


What would be perfect would be if there were an anamorphic lens that gave a 2.40:1 image FROM a 1.33:1 (or 4:3) shape...I've read before that they exist, albeit are very rare.
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

[quote author=Barry_Green link=board=Events;num=1086609729;start=0#2 date=06/07/04 at 09:56:16]Well, it'll sort of work -- you'll end up with a vignetted 2.66:1 image, which will be severely squeezed in the viewfinder and nearly impossible to properly compose for the aspect ratio.  People complain about the 1.33 squeeze factor of the Panasonic anamorphic... trying to compose with a 3x stronger squeeze will be quite difficult.
[/quote]

Sorry, adaptor is 1.75X, no 2x. This provides 2.40 aspect ratio, or a 2:1 pixel aspect ratio, 2.66 Ultrascope would need a 2x adaptor and is out of use nowadays.

Composing for this aspect ratio would need a video processor (analog) to adjust heigth to feed a letterboxed image to a field monitor. A cheapest way is to feed firewire signal to a laptop an use a realtime preview sofware to corecct the aspect ratio (BTVPro, WinDV).

And then, what will you do with the image?  If you're planning on making a film print, you'll have to chop off image from the sides, which will result in a resolution loss.  If you're planning on making an anamorphic DVD you'll have to unsqueeze it in post to 16:9, which will result in a 33% resolution loss.
Click to expand...

No chop. You simply transfer the raw 4/3 squeezed image on the full academy 35mm frame, so you get a cinemascope print that, when projected trought a cinemascope lens, would provide a corrected image with a 2.40 aspect ratio

In the DVD, you simply letterbox it to 16/9, so you end up with a half letterboxed, half anamorphosized image, that is recognised as 16/9 image (so aspect ratio corrected by the player) getting the full 2.35 image into the 4/3 or 16/9 image.
In fact, 1.75x anamorphosis is the only method to retain full resolution power when composing in 2.40 1. You can crop a 16/9 image (obtained with the panasonic adapter) getting a 720*405 image, or crop a full frame, getting a 720 *300 image.

Jose
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

Ah...if you have an anamorphic that'll give you true 2.40:1 anyways...then there's no problem with the film print, at least I wouldn't think there would be.

Barry?? ;D
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

[quote author=Mike_Donis link=board=Events;num=1086609729;start=0#5 date=06/07/04 at 15:39:22]The thing is, you're losing resolution when getting a 2.40:1 image from a 2:1 anamorphic lens...

With 35mm, the negative area used in anamorphic photography comes to about 1.2:1, NOT 4:3.  The entire 35mm frame is 4:3, yes, but due to the optical soundtrack on the film, space is lost on the sides...the fact that nobody uses the crappy quality audio track is irrelevant; we still chop it off, so that when we stretch the width of the frame by 2, as with a 2:1 lens, we get approximately 2.40:1.
[/quote]

Sh*t.. You right. I supposse I have to review my American Cinematographer manual ;-).

The fact is, I've seen a dv movie shoot by the double 16/9 method, I mean, anamorphic adapter and in camera 16/9 to get it, but it crops the image, so resolution is loss again...
www.campslaugther.com

Using that same lens, with DV, as Barry has already mentioned, gets you a 2.66:1 image, NOT a 2.40:1 image.  So in order to get a 2.40 frame, you'd need to actually crop the sides of the image (Barry already discussed this).  So because you're throwing away resolution in order to get 2.40 anyways, why not save the trouble of anamorphic in the first place.
Click to expand...

Loss would be around 187 pixels, width, keeping full vertical resolution...

Anybody know how many vertical / horizontal resolution lines for this camera?

What would be perfect would be if there were an anamorphic lens that gave a 2.40:1 image FROM a 1.33:1 (or 4:3) shape...I've read before that they exist, albeit are very rare.
Click to expand...

Yes. I wish I could get one. What would be the squeezing factor? 1.8, 1.75x, I suppose?.

Jose
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

Kowa 1.75X anamorphic!!!

It exists, however, It's about half the price of the DVX100... And that if you get one, because BBC guys are chasing them around the globe...

Thanks for your wise ideas... I'll keep trying ;-)

Jose
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

That was the one I heard about...the Kowa...

So wait, howcome it's a problem, if you have an adaptor that squeezes to 2.40?
 
Re: NEED HELP: Measures of lens element. 2.40  AS

Re: NEED HELP: Measures of lens element. 2.40  AS

Hmmm... interesting prospect. Yes, there are some 1.75 anamorphics out there, and there's even some 1.5x. 1.75 would get you about 2.33:1, which is within a pixel or two of 2.39:1, so yeah, that might work!

For display on a DVD or 16:9 TV you'll still be unsqueezing it in post, but depending on the quality of the lens, you may have a clean-enough source (and you'll be down-rezzing which preserves image better) so maybe that'd work.

Sounds like something to play with. I don't know if it'll be a practical production solution, because the question becomes: are there any film houses that will transfer your 1.75:1-squeezed 1.33 image onto a 2:1-squeezed 1.2:1 film frame? And if so, will they charge you a fortune for it? And are you *really* going to blow up to film? And, will you be able to find a monitor that will let you view the image unsqueezed-enough for proper composition? If you can find satisfactory answers to all those questions, it sounds like it would make for an interesting experiment!
 
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