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35mm Adapter Properties


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#1 Anna Uio

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Posted 20 January 2009 - 01:08 PM

Howdy,

Whenever I read about 35mm lens adapters for video cameras, there is always lots of discussion of depth of field. That's great, but no one ever seems to mention another consequence of having a much larger equivalent film gauge, namely MUCH wider field of view without having to use a short lens or back the camera away from the subject. Am I missing something? Isn't this important too?

In comparing my own cameras with different sensor sizes ( 0.25in to 0.55in ), the difference has an enormous effect on the geometry of shooting a scene, i.e. relative placement and motion of objects in the frame, especially when the camera or subjects are moving relative to each other.

Cheers,
Anna
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#2 James Martin

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Posted 20 January 2009 - 05:23 PM

I'm not quite sure what you're getting at here... do you mean that 35mm adapters let you shoot "wider" scenes? If that is the case... there are plenty of low-cost HD(v) cameras with very wide lenses... In the 2/3" format a couple of lenses I know off the top of my head do something like 4.7mm or 4.5mm - that's equivalent to about 28mm in 35mm still camera terms - it's very wide.

Am I missing your meaning here, perhaps I just don't understand?
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#3 Brian Drysdale

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Posted 20 January 2009 - 05:32 PM

You're getting a shallower DOF because you're using a longer focal length lens for the equivalent angle of view that your video camera would be using. You have to rethink the angles of view for each focal length otherwise if you just use the same focal length on both the 35mm adapter as on the video camera, the former will have a wider angle of view.
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#4 Anna Uio

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Posted 21 January 2009 - 04:39 PM

Here is a nice web page that calculates field of view from focal length and format:

http://www.mat.uc.pt...tos/angles.html

My question wasn't about how this works, but rather asking why it is so seldom discussed compared to depth of field. The weird wide-angleness/tiny field of view of video cameras is what makes everything shot on them so recognizable and looks so bad in my opinion, not the depth of field. It creates such bizarre geometric relationships between objects in the fore, mid and background.

Cheers,
Anna
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#5 Brian Drysdale

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Posted 21 January 2009 - 05:29 PM

Here is a nice web page that calculates field of view from focal length and format:

http://www.mat.uc.pt...tos/angles.html

My question wasn't about how this works, but rather asking why it is so seldom discussed compared to depth of field. The weird wide-angleness/tiny field of view of video cameras is what makes everything shot on them so recognizable and looks so bad in my opinion, not the depth of field. It creates such bizarre geometric relationships between objects in the fore, mid and background.

Cheers,
Anna


On the 1/3" video cameras it could just be the lenses are made to a price and they have levels of barrel distortion that hasn't been corrected in the design. Interestingly the Zeiss Contex 35 mm stills lens that I used on my Aaton 16mm camera had some barrel distortion whereas the Zeiss 25mm Super Speed Distagon 16mm film lens had no noticeable barrel distortion.
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#6 Matthew Oaten

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Posted 22 January 2009 - 03:54 AM

Here is a nice web page that calculates field of view from focal length and format:

http://www.mat.uc.pt...tos/angles.html

My question wasn't about how this works, but rather asking why it is so seldom discussed compared to depth of field. The weird wide-angleness/tiny field of view of video cameras is what makes everything shot on them so recognizable and looks so bad in my opinion, not the depth of field. It creates such bizarre geometric relationships between objects in the fore, mid and background.

Cheers,
Anna

I have jut finished building my own 35mm adapter, and time permitting, I may run some tests today to see :) Although I only have a 50mm prime, nothing shorter unfortunately. As the video camera is recording the 35mm lens projection onto a piece of ground glass, you still have the restriction of framing the ground glass/focusing screen with the video camera, which cuts down the field of view somewhat already, and may perhaps lose any benefit gained from the shorter focal distance. As far as I am concerned the primary objective of my 35mm adapter is to allow selective focusing and a shallow dof by allowing a faster/shorter 35mm lens to be attached to my video camera to achieve a more filmic look on my restricted budget. I'm kinda new to this, so please don't castrate me for any inconsistencies/lack of understanding!
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#7 David Auner aac

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Posted 22 January 2009 - 02:27 PM

My question wasn't about how this works, but rather asking why it is so seldom discussed compared to depth of field. The weird wide-angleness/tiny field of view of video cameras is what makes everything shot on them so recognizable and looks so bad in my opinion, not the depth of field. It creates such bizarre geometric relationships between objects in the fore, mid and background.


Hi Anna,
I'm not quite sure I get what you are saying. When you use a very wide lens on a video camera, say a 2/3" that would be a 4.5mm lens. And on 35mm cine film you'd use a 12mm lens lens to get roughly the same angle. So what is the difference you perceive here? Are you saying that video cameras generally lack wide angle zoom lenses or that they are too wide?

Regards, Dave
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#8 Anna Uio

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Posted 22 January 2009 - 06:58 PM

Here is a nice video review of the Canon EOS 5D Mark II, a full frame (35mm) digital SLR that can shoot movies. The reviewer talks about getting greater "coverage" with the larger format than is possible with normal small chip video cameras when using a lens with the same focal length. Just looking at their example clips one can see how much more of a scene can be shot without resorting to as wide angle lenses and the associated perspective. As another example, search for online for medium format photographs and notice how they "look different". The difference is again that you can see so much of the scene but without using wide angle perspective. Finally, one can watch films shot in 70mm and see this. Warning: once you learn to see it, you will hate anything shot on tiny video cameras, including the best 2/3" prosumer models :)


View on Vimeo

Cheers,
Andrew

Edited by Anna Uio, 22 January 2009 - 06:58 PM.

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#9 Brian Drysdale

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Posted 23 January 2009 - 09:50 AM

I'd expect there to be greater "coverage" (larger angle of view) at a particular focal length with a full frame 35mm camera compared to using the same focal length on say either a 1/3 or 2/3" camera.

I'm not sure if what you're really getting at is the increased detail that you can see on the larger formats compared to smaller formats. That would've been the main reason for going for them in the past rather than the shallow DOF effect, which is a much more recent obsession. Traditionally this was reason why people shot on 35mm as against 16mm rather than the DOF.
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#10 David Auner aac

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Posted 23 January 2009 - 10:36 AM

Just looking at their example clips one can see how much more of a scene can be shot without resorting to as wide angle lenses and the associated perspective.


Hi Anna,

what you are saying here is just not correct. Focal lengths don not change when used on different cameras but the FOV of different cameras in different formats (video chip sizes or film gauges) is different when using the same focal length. Just take a look at medium format photos taken with the a Hasselblad and the Zeiss 30mm fisheye and compare these to pics taken with a Canon/Nikon and a 14 or 16mm fisheye. Same perspective! And if you use a 35mm lens on a really small sensor camera the perspective WILL BE different to when you use it on a 35mm still SLR!

Regards, Dave
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#11 Anna Uio

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Posted 26 January 2009 - 12:35 AM

The FOV of different cameras in different formats (video chip sizes or film gauges) is different when using the same focal length.


Thanks Dave. That's exactly what I thought I was saying, or what I was trying to say at least :) I certainly never meant to imply that the focal length of a lens somehow changed from camera to camera!

And my actual original question was only to wonder why people do not talk about this more. It has such a huge effect on how you shoot a scene. With a larger format, you don't have to use as wide angle of a lens to "take in a scene" and thus you can shoot with less of the "huge in the foreground, tiny in the background" that I think is the most recognizable characteristic of stuff shot on video cameras. Even supposedly big chip cameras that still don't get anywhere near 35mm film. I dream of the day when larger frame cameras like the Red become more popular and come more down even more in price.

Cheers,
Anna
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#12 Satsuki Murashige

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Posted 26 January 2009 - 03:43 AM

The geometric properties of a wide angle rectilinear lens, whether it's a 24mm Nikkor still lens or an 18mm Zeiss Superspeed, are impossible image characteristics to get with most 1/3" chip cameras without the use of a 35mm adapter. This is because most of the lenses that come with those cameras require a wide angle lens adapter or converter to get anywhere near the same field of view as a 35mm lens in the 18-24mm range, and the adapter is non-rectilinear so the image always has some barrel distortion to it. The ability to get a rectilinear wide field of view makes a big difference in look - I've always felt that this effect of a 35mm adapter was more important than shallow depth in creating the "film look." Of course, you can also get wide angle rectilinear lenses in 16mm and 2/3" formats, just with more depth of field.
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#13 David Auner aac

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Posted 29 January 2009 - 01:11 PM

Hi Anna,

I fully subscribe to what Satsuki is saying but I think that there is one more thing you're maybe hinting at. The larger the film gauge/format, the lower the magnification. For me at least, that does something to an image I can't really define. When looking at a large format photograph or a 70mm cine film there is something about the image that is really pleasing to me, but not only explained by the superior resolution et al. Maybe that's what you're seeing/feeling too.

Cheers, Dave
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#14 Anna Uio

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Posted 17 March 2009 - 01:50 AM

I happened upon another reference to the concept I was trying to discuss on

http://www.dpreview....ey=focal length

in the first paragraph in particular

> Larger sensors or films have wider FOVs and can capture more of the scene.

And a depth of field adapter give you in effect a full frame sensor :)

Cheers,
Anna
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