The widest angle with no BD? at DVinfo.net

Rafael Lopes · February 3rd, 2008, 04:04 AM

Hi guys,

I was recently offered to buy a 15mm lens and I was wondering if it's really worth it. I mean I LOVE super wide shots, but I've seen pictures taken with a 15mm and there's a lot of barrel distortion....on the other hand I've seen G35 footage with a 14mm and the bd was not that evident (even though it was there). What is the widest one could go using a 35mm adapter without DB? The wides lens I have is a 24mm but more than once I found my self thinking "Boy, I sure could go wider than this in this situation".

Ted Ramasola · February 3rd, 2008, 07:01 AM

Rafael,

the Sigmas from 15-30mm and 20-40mm range have no barrel distortion if you dont get the model that they label as fisheye.

I have attached them both to my adapter and the diagonals and verticals stay straight.

Im attaching a grab from both lenses for you to guage.

The 15 has slight corner falloff that you may or may not like. but since its a 15-30mm fullframe zoom you can adjust it. I recommend the 20-40mm f2.8 because its faster and no falloff.

DO NOT gauge these grabs for sharpness because its a DIY adapter but do guage it for lens FOV of the sigmas on an adapter.

I added a grab from a 50mm shot from the same position as the 20mm for you to appreciate and compare the fov.

Ted

Rafael Lopes · February 3rd, 2008, 08:57 AM

This helps a lot. I would expect the 15mm to be full of barrel distortion but apparently not. Thanks, Ted.

Bob Hart · February 3rd, 2008, 09:06 AM

The Nikon 12mm-24mm f4 zoom is also a rectilinear lens (true straight edges and diagonals. It has the effect like all of this type to stretch the image in the diagonal directions which is how it gets the edges straight.

You need to make sure the optical centres of the adaptor are true, otherwise there is a diagonal distortion which has the appearance of some sort of barrel distortion.

This lens is also for digital SLRs not film. On wide format adaptors it may vignette on the wide end of the zoom. There is only one stop of headroom between this lens wide-open aperture and the accepted safe limit of f5.6 for groundglass work.

I have mentioned this lens previously so the comment may be quite boring by now. Here's a link to equally boring test footage in which the 12mm - 24mm was used.

http://www.youtube.com/watch?v=WokhLQv7fQE

This footage was shot on an adaptor which was not correctly centred. The optical centre was low and left as viewed (high and right in the adaptor).

The 14mm f2.8 by Nikon and equivalents, also rectilinear, are handy lenses for tight places for those who do not want to shoot direct-to-camera.

There may be a few remaining specimens of the Kinoptik Tegea 9.8mm f1.8 (T2.3) that Red users have not yet scooped up. These come often with older mount styles. This is also a rectilinear lens.

This is a big 35mm brother to the Kinoptik Tegea 5.7mm f1.8 lens for 16mm cams, apparently sometimes called the "Rodriguez" lens because Robert Rodriguez used it on "El Mariachi".

The used cost may be a bit high for adaptor builders or alternative adaptor buyers. This lens was apparently also rebarrelled by Century with lens gears and PL mount and fetches a higher price used.

David W. Jones · February 3rd, 2008, 10:25 AM

Also be aware that these wider lenses can exhibit vignetting, which is dependent on the lens and ground glass adapter combination.

February 3rd, 2008, 04:04 AM	#1
Rafael Lopes Trustee Join Date: Sep 2005 Location: Rio de Janeiro Posts: 1,239	The widest angle with no BD? Hi guys, I was recently offered to buy a 15mm lens and I was wondering if it's really worth it. I mean I LOVE super wide shots, but I've seen pictures taken with a 15mm and there's a lot of barrel distortion....on the other hand I've seen G35 footage with a 14mm and the bd was not that evident (even though it was there). What is the widest one could go using a 35mm adapter without DB? The wides lens I have is a 24mm but more than once I found my self thinking "Boy, I sure could go wider than this in this situation".

February 3rd, 2008, 07:01 AM	#2
Ted Ramasola Trustee Join Date: May 2005 Location: Allen, Texas U.S.A Posts: 1,117	Rafael, the Sigmas from 15-30mm and 20-40mm range have no barrel distortion if you dont get the model that they label as fisheye. I have attached them both to my adapter and the diagonals and verticals stay straight. Im attaching a grab from both lenses for you to guage. The 15 has slight corner falloff that you may or may not like. but since its a 15-30mm fullframe zoom you can adjust it. I recommend the 20-40mm f2.8 because its faster and no falloff. DO NOT gauge these grabs for sharpness because its a DIY adapter but do guage it for lens FOV of the sigmas on an adapter. I added a grab from a 50mm shot from the same position as the 20mm for you to appreciate and compare the fov. Ted Attached Thumbnails Last edited by Ted Ramasola; February 3rd, 2008 at 07:17 AM. Reason: added text and image

February 3rd, 2008, 09:06 AM	#4
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	The Nikon 12mm-24mm f4 zoom is also a rectilinear lens (true straight edges and diagonals. It has the effect like all of this type to stretch the image in the diagonal directions which is how it gets the edges straight. You need to make sure the optical centres of the adaptor are true, otherwise there is a diagonal distortion which has the appearance of some sort of barrel distortion. This lens is also for digital SLRs not film. On wide format adaptors it may vignette on the wide end of the zoom. There is only one stop of headroom between this lens wide-open aperture and the accepted safe limit of f5.6 for groundglass work. I have mentioned this lens previously so the comment may be quite boring by now. Here's a link to equally boring test footage in which the 12mm - 24mm was used. http://www.youtube.com/watch?v=WokhLQv7fQE This footage was shot on an adaptor which was not correctly centred. The optical centre was low and left as viewed (high and right in the adaptor). The 14mm f2.8 by Nikon and equivalents, also rectilinear, are handy lenses for tight places for those who do not want to shoot direct-to-camera. There may be a few remaining specimens of the Kinoptik Tegea 9.8mm f1.8 (T2.3) that Red users have not yet scooped up. These come often with older mount styles. This is also a rectilinear lens. This is a big 35mm brother to the Kinoptik Tegea 5.7mm f1.8 lens for 16mm cams, apparently sometimes called the "Rodriguez" lens because Robert Rodriguez used it on "El Mariachi". The used cost may be a bit high for adaptor builders or alternative adaptor buyers. This lens was apparently also rebarrelled by Century with lens gears and PL mount and fetches a higher price used. Last edited by Bob Hart; February 3rd, 2008 at 09:09 AM. Reason: added URL

February 3rd, 2008, 08:57 AM	#3
Rafael Lopes Trustee Join Date: Sep 2005 Location: Rio de Janeiro Posts: 1,239	This helps a lot. I would expect the 15mm to be full of barrel distortion but apparently not. Thanks, Ted.

February 3rd, 2008, 10:25 AM	#5
David W. Jones Trustee Join Date: Dec 2006 Location: Little Rock Posts: 1,383	Also be aware that these wider lenses can exhibit vignetting, which is dependent on the lens and ground glass adapter combination.