Wide Angle Lens Converter for GL / XM

Graham Bernard · May 16th, 2003, 08:01 AM

Rick - Ditto - Big Time!

Grazie

Wayne Orr · May 16th, 2003, 09:08 AM

I just wanted to provide this link again to a depth of field chart. Maybe if you see it in print, Brad, your keen engineering mind will accept what your filmmaker's heart wants to ignore:
http://www.panavision.co.nz/kbase/op...alcFOVform.asp

Rick Spilman · May 16th, 2003, 09:31 AM

Great chart, Wayne! Thanks.

(Whenever I have actually tried to calculate DOF I always end up falling into the circle of confusion myself.)

Brad Higerd · May 17th, 2003, 07:17 AM

The whole DOF came by accident during an interview shoot on a local university campus. The sun was going down, and I was forced to open the iris all the way. It wasn't until I went to edit the footage sometime later that DOF first sparked and obsessive reaction. I liked it then, and I like it now. However, I do agree with Rick about the possibilities of overdoing it. The "Images" from Michael Pappas on the GL2 Watchdog website are still some of my favorites, and I really like the DOF of some of these images.

Thank you all again for you input. This site has become my favorite forum because of folks like you.

Brad

Graham Bernard · May 17th, 2003, 12:45 PM

"Here's Lookin' at you kid!"

Val Rodriguez · May 17th, 2003, 03:13 PM

One technique that can be used to produce "narrow" or "shallow" DOF is to film your subject with a telephoto lens or in the case of the GL2 increase your distance to your subject and zoom in. The result will be a very shallow DOF. Another benefit will be that filming/photographing people in telephoto mode produces a very flattering image of the human face as a result of the lens ability to compress or flatten the field of view. By contrast wide angle filming exagerates facial features (read nose look bigger).

Jeff Donald · May 17th, 2003, 08:04 PM

Hi Val and Welcome to DV Info. Thanks for posting your thoughts on DOF and the compression abilities of telephoto lenses. However, you may want to take a look at the Ultimate DOF thread for a more complete look at all of the factors and how they interact.

Val Rodriguez · May 18th, 2003, 12:27 PM

Jeff,
Thanks, for the welcome and the link to the ultimate DOF thread(still digesting the info). Fascinating to see people fiercely disagree about a subject but still maintain a cordial attitude.

Back to DOF. I am planning to do a side by side comparison of DOF with my GL2 and my Nikon F3 with a 300 mm telephoto lens. One difficulty will to accurately simmulate the equivalent zoom with the GL2...any thoughts?.

Jeff Donald · May 18th, 2003, 12:59 PM

I've got several posts on that in the archives. Use the search function and search >chip size< and my name. It should turn up what your looking for. The factor is basically 9.x for the small chip. Multiply the focal length of the GL2 by 9.X to determine the approximate 35mm equivalent.

Wayne Orr · May 18th, 2003, 02:58 PM

Ahh, the search for the "Holy Grail" for shallow depth of field with small chip cameras continues.

Val, if you will familiarize yourself with the Depth of Field guide from Panavision, you will get a lot of the answers to your questions.
http://www.panavision.co.nz/kbase/op...alcFOVform.asp
For example, using your 35mm still camera with a 300mm lens at twenty feet at f/2.8, we calculate an effective depth of field of just over two inches. Very nice shallow depth of field.

Convert the 300mm lens to the one-quarter inch chip GL2 camera, by dividing 300 by 9.2, we end up with a 32mm lens on your GL2. Calculatin that on the guide, at twenty feet at f/2.8, we have a depth of field of almost five and one half feet! And remember; the focus gradually softens, rather than the more abrupt fall off you will get with the 35mm still camera format.

What you are saying is basically correct, Val; long lens equals shallow depth of field, but the narrow depth of field is nowhere near as dramatic on small chip cameras as on 35mm formats. It simply is not possible for the aspiring filmmaker to get the same shallow depth of field shots that we see in motion pictures. And with a wide angle lens that the original poster asked about, it is absolutely out of the question. The only "trick" that could be used is with a camera that has macro lens capability, but that is a different issue.

Val Rodriguez · May 18th, 2003, 04:20 PM

Jeff, Wayne,
Thanks for the links and comments. The information is overhelmingly convincing that shallow DOF is a near impossibility with a 1/4 chip. It is a real disappointment because I've widely used shallow DOF in my photography and wanted to widely(or narrowly) use it in filming with my GL2.

But all is not lost, as I've read numerous comments on this board, the use of aperture and ND's and even polarizing filters combined with other techniques may yield an acceptable level of shallow DOF.

Jeff Donald · May 18th, 2003, 04:38 PM

The trick for shallow DOF is to always shot at the widest aperture (smallest numerical F number, F1.6, F2.0, or F2.8). This doesn't guarantee the results will be what you hope for. But rather, the shallowest given your choice of medium and equipment. Longer focal length lenses (telephoto) will have shallower DOF than shorter focal length lenses (wide angle). The further you are from your subject the larger the DOF, closer to subject the shallower the DOF.

Don't get caught in the trick of moving further away and zooming in. The DOF will stay the same.

Given the limits of our medium (small format video) the following will give you the shallowest or least amount of DOF.

1. Use the longest (largest) focal length lens.

2. Use largest lens opening (smallest numerical F number).

3. Get as close to your subject as possible.

Food for additional thought, see my post here.

Wayne Orr · May 18th, 2003, 04:44 PM

Rob writes:

"But all is not lost, as I've read numerous comments on this board, the use of aperture and ND's and even polarizing filters combined with other techniques may yield an acceptable level of shallow DOF."

Of course I don't know what you consider "acceptable," but have you seen any pictures? Your camera will shoot at f/1.6 (I believe) at the wide end. As you increase the focal length, that f/stop will change to eventually f/2.9. You can add all the ND's and pola filters you want, you still can only shoot at the available maximum stop for the focal length. The only way that you can gobble up more light and narrow the depth of field, is to shoot at a higher shutter speed, and accept the motion effects this high rate will cause, which are unacceptable to almost everyone for normal shooting situations.

I am not trying to pick on you, Rob, but you are making it sound like there is some magic workaround for this limitation, and there really is not.

Val Rodriguez · May 18th, 2003, 09:50 PM

Wayne,
I didn't mean to imply there was a magic workaround. I was merely indicating that by using max aperture, ND filters and other techniques like Jeff and others suggested, one could achieve certain reduction of DOF and at this point ANY reduction of DOF would be acceptable given the limitations of the medium.

Miles Blow · May 18th, 2003, 10:54 PM

Hi Guys
We had a terrable time trying to get a narrow depth of field on our canon g2(still camera)and our xm2. We were useing it for stopmotion animation purposes. As the g2 has a very lame 3x zoom lens everything was wide angle looking and all in sickening focus.
So we did lots of experimenting to try amd combat this. One way was to stick a magnifying glass in front of the lens making a macro lens which creates epic depth of field but only when you are 1 ft away from your subject. usable for some animation purposes but not something viable for live action shooting. It works with our xm2 aswell. But the best results we got were useing a homemade mini35 adaptor(same principles as the ps technik adaptor for the xl1-pd150) This consited of a 35mm stills lens mounted on a box which has a spinning ground glass about an inch from the back of the lens. This creates an epicly shallow depth of field on the surface of the ground glass with the 35mm lens cranked openf1.7. The only problem now is that the image created was upside down. But because we were useing out little g2 for the shooting of this image we just flipped the camera on the back of the box upsideown. Next problem was the g2 couldent focus on the ground glass as the rear projected image is only 35mm in size so we glued a 50mm stills lens on to a 58mm step down/ step up/stepdown ring. so now it screws onto the front of the g2. (thus creating an extream macro) Now we can shoot a 35mm image onto film resolution digital still. This technique works fine on the our xm2 aswell. As the 58mm thread fits the front of the xm2/gl2and our g2. The only reason we havent built a version for our xm2 is that we don't want our xm2 to be costantly upsidedown. Might hurt the camera(seeing it cost a sh*tload more than or g2)!! So the solution will be a parallex mirror setup to correct the upside down image (a fair bit of messing around) and we will have a xm2/gl2 that shoots with a 35mm dof. If anyone is interested in seeing some photos you can email me Mulesfilmworks@optusnet.com.au
Sorry if you found these technical detail boring!

May 16th, 2003, 09:08 AM	#122
Wayne Orr Major Player Join Date: Dec 2002 Location: Northridge Ca Posts: 734	I just wanted to provide this link again to a depth of field chart. Maybe if you see it in print, Brad, your keen engineering mind will accept what your filmmaker's heart wants to ignore: http://www.panavision.co.nz/kbase/op...alcFOVform.asp __________________ Wayne If it was easy, they'd get a relative to do it.

May 17th, 2003, 12:45 PM	#125
Graham Bernard Old Boot Join Date: Aug 2002 Location: London UK Posts: 3,633	. . . thanks Brad . . . "Here's Lookin' at you kid!"

May 17th, 2003, 03:13 PM	#126
Val Rodriguez Regular Crew Join Date: May 2003 Location: Mission Viejo, CA Posts: 35	One technique that can be used to produce "narrow" or "shallow" DOF is to film your subject with a telephoto lens or in the case of the GL2 increase your distance to your subject and zoom in. The result will be a very shallow DOF. Another benefit will be that filming/photographing people in telephoto mode produces a very flattering image of the human face as a result of the lens ability to compress or flatten the field of view. By contrast wide angle filming exagerates facial features (read nose look bigger). __________________ Val Rod

May 17th, 2003, 08:04 PM	#127
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	Hi Val and Welcome to DV Info. Thanks for posting your thoughts on DOF and the compression abilities of telephoto lenses. However, you may want to take a look at the Ultimate DOF thread for a more complete look at all of the factors and how they interact. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

May 18th, 2003, 12:27 PM	#128
Val Rodriguez Regular Crew Join Date: May 2003 Location: Mission Viejo, CA Posts: 35	Jeff, Thanks, for the welcome and the link to the ultimate DOF thread(still digesting the info). Fascinating to see people fiercely disagree about a subject but still maintain a cordial attitude. Back to DOF. I am planning to do a side by side comparison of DOF with my GL2 and my Nikon F3 with a 300 mm telephoto lens. One difficulty will to accurately simmulate the equivalent zoom with the GL2...any thoughts?. __________________ Val Rod

May 16th, 2003, 08:01 AM	#121
Graham Bernard Old Boot Join Date: Aug 2002 Location: London UK Posts: 3,633	Rick - Ditto - Big Time! Grazie

May 16th, 2003, 09:31 AM	#123
Rick Spilman Major Player Join Date: Dec 2002 Location: Jersey City, NJ Posts: 366	Great chart, Wayne! Thanks. (Whenever I have actually tried to calculate DOF I always end up falling into the circle of confusion myself.)

May 17th, 2003, 07:17 AM	#124
Brad Higerd Regular Crew Join Date: Jan 2003 Location: Orlando, FL Posts: 186	The whole DOF came by accident during an interview shoot on a local university campus. The sun was going down, and I was forced to open the iris all the way. It wasn't until I went to edit the footage sometime later that DOF first sparked and obsessive reaction. I liked it then, and I like it now. However, I do agree with Rick about the possibilities of overdoing it. The "Images" from Michael Pappas on the GL2 Watchdog website are still some of my favorites, and I really like the DOF of some of these images. Thank you all again for you input. This site has become my favorite forum because of folks like you. Brad

May 18th, 2003, 12:59 PM	#129
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	I've got several posts on that in the archives. Use the search function and search >chip size< and my name. It should turn up what your looking for. The factor is basically 9.x for the small chip. Multiply the focal length of the GL2 by 9.X to determine the approximate 35mm equivalent. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

May 18th, 2003, 02:58 PM	#130
Wayne Orr Major Player Join Date: Dec 2002 Location: Northridge Ca Posts: 734	Ahh, the search for the "Holy Grail" for shallow depth of field with small chip cameras continues. Val, if you will familiarize yourself with the Depth of Field guide from Panavision, you will get a lot of the answers to your questions. http://www.panavision.co.nz/kbase/op...alcFOVform.asp For example, using your 35mm still camera with a 300mm lens at twenty feet at f/2.8, we calculate an effective depth of field of just over two inches. Very nice shallow depth of field. Convert the 300mm lens to the one-quarter inch chip GL2 camera, by dividing 300 by 9.2, we end up with a 32mm lens on your GL2. Calculatin that on the guide, at twenty feet at f/2.8, we have a depth of field of almost five and one half feet! And remember; the focus gradually softens, rather than the more abrupt fall off you will get with the 35mm still camera format. What you are saying is basically correct, Val; long lens equals shallow depth of field, but the narrow depth of field is nowhere near as dramatic on small chip cameras as on 35mm formats. It simply is not possible for the aspiring filmmaker to get the same shallow depth of field shots that we see in motion pictures. And with a wide angle lens that the original poster asked about, it is absolutely out of the question. The only "trick" that could be used is with a camera that has macro lens capability, but that is a different issue. __________________ Wayne If it was easy, they'd get a relative to do it.

May 18th, 2003, 04:20 PM	#131
Val Rodriguez Regular Crew Join Date: May 2003 Location: Mission Viejo, CA Posts: 35	Jeff, Wayne, Thanks for the links and comments. The information is overhelmingly convincing that shallow DOF is a near impossibility with a 1/4 chip. It is a real disappointment because I've widely used shallow DOF in my photography and wanted to widely(or narrowly) use it in filming with my GL2. But all is not lost, as I've read numerous comments on this board, the use of aperture and ND's and even polarizing filters combined with other techniques may yield an acceptable level of shallow DOF. __________________ Val Rod

May 18th, 2003, 04:38 PM	#132
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	The trick for shallow DOF is to always shot at the widest aperture (smallest numerical F number, F1.6, F2.0, or F2.8). This doesn't guarantee the results will be what you hope for. But rather, the shallowest given your choice of medium and equipment. Longer focal length lenses (telephoto) will have shallower DOF than shorter focal length lenses (wide angle). The further you are from your subject the larger the DOF, closer to subject the shallower the DOF. Don't get caught in the trick of moving further away and zooming in. The DOF will stay the same. Given the limits of our medium (small format video) the following will give you the shallowest or least amount of DOF. 1. Use the longest (largest) focal length lens. 2. Use largest lens opening (smallest numerical F number). 3. Get as close to your subject as possible. Food for additional thought, see my post here. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

May 18th, 2003, 04:44 PM	#133
Wayne Orr Major Player Join Date: Dec 2002 Location: Northridge Ca Posts: 734	Rob writes: "But all is not lost, as I've read numerous comments on this board, the use of aperture and ND's and even polarizing filters combined with other techniques may yield an acceptable level of shallow DOF." Of course I don't know what you consider "acceptable," but have you seen any pictures? Your camera will shoot at f/1.6 (I believe) at the wide end. As you increase the focal length, that f/stop will change to eventually f/2.9. You can add all the ND's and pola filters you want, you still can only shoot at the available maximum stop for the focal length. The only way that you can gobble up more light and narrow the depth of field, is to shoot at a higher shutter speed, and accept the motion effects this high rate will cause, which are unacceptable to almost everyone for normal shooting situations. I am not trying to pick on you, Rob, but you are making it sound like there is some magic workaround for this limitation, and there really is not. __________________ Wayne If it was easy, they'd get a relative to do it.

May 18th, 2003, 09:50 PM	#134
Val Rodriguez Regular Crew Join Date: May 2003 Location: Mission Viejo, CA Posts: 35	Wayne, I didn't mean to imply there was a magic workaround. I was merely indicating that by using max aperture, ND filters and other techniques like Jeff and others suggested, one could achieve certain reduction of DOF and at this point ANY reduction of DOF would be acceptable given the limitations of the medium. __________________ Val Rod

May 18th, 2003, 10:54 PM	#135
Miles Blow New Boot Join Date: Mar 2003 Location: Queensland Australia Posts: 7	Hi Guys We had a terrable time trying to get a narrow depth of field on our canon g2(still camera)and our xm2. We were useing it for stopmotion animation purposes. As the g2 has a very lame 3x zoom lens everything was wide angle looking and all in sickening focus. So we did lots of experimenting to try amd combat this. One way was to stick a magnifying glass in front of the lens making a macro lens which creates epic depth of field but only when you are 1 ft away from your subject. usable for some animation purposes but not something viable for live action shooting. It works with our xm2 aswell. But the best results we got were useing a homemade mini35 adaptor(same principles as the ps technik adaptor for the xl1-pd150) This consited of a 35mm stills lens mounted on a box which has a spinning ground glass about an inch from the back of the lens. This creates an epicly shallow depth of field on the surface of the ground glass with the 35mm lens cranked openf1.7. The only problem now is that the image created was upside down. But because we were useing out little g2 for the shooting of this image we just flipped the camera on the back of the box upsideown. Next problem was the g2 couldent focus on the ground glass as the rear projected image is only 35mm in size so we glued a 50mm stills lens on to a 58mm step down/ step up/stepdown ring. so now it screws onto the front of the g2. (thus creating an extream macro) Now we can shoot a 35mm image onto film resolution digital still. This technique works fine on the our xm2 aswell. As the 58mm thread fits the front of the xm2/gl2and our g2. The only reason we havent built a version for our xm2 is that we don't want our xm2 to be costantly upsidedown. Might hurt the camera(seeing it cost a sh*tload more than or g2)!! So the solution will be a parallex mirror setup to correct the upside down image (a fair bit of messing around) and we will have a xm2/gl2 that shoots with a 35mm dof. If anyone is interested in seeing some photos you can email me Mulesfilmworks@optusnet.com.au Sorry if you found these technical detail boring!