50mm 1/1.7 lens vs a 55mm 1/3.5 lens at DVinfo.net

Quito Washington · January 3rd, 2006, 03:46 AM

pardon my ignorance but for minimizing depth of field, which would be the better lens? and whats the difference in the two lens anyways, what does the 1.7 or 3.5 refer to exactly?
I shot an email to Declan (knowledgable guy that he is) but thought i would open it up to the crowd as well in case anyone had any thoughts...
cheers
Q

Carl Jakobsson · January 3rd, 2006, 03:58 AM

The values you are refering to is the f-number.

Check this out
http://en.wikipedia.org/wiki/Aperture

A summary:
Low f-number=fast lens=big aperture=brighter=less vignetting=shorter DOF=expensive

For a 35mm adapter you would probably want a fast lens. 1.7 is "semi"-fast, 1.4 is really fast, and 1.2 is extremely fast. Around 2.0 is mostly standard on SLRs.

Quito Washington · January 3rd, 2006, 04:07 AM

so, according to your post, and to the article, i should use that 1.7 with a high shutter speed to achieve minimum DoF (the least amount in focus)?
Q

Tom Hardwick · January 3rd, 2006, 04:38 AM

Yes, the faster lens (the one with the wider aperture) will give shots with more differential focus if used at those wider apertures. Both lenses will give the same dof if used at the same aperture of course.

Most good 35 mm SLR lenses have dof scales that relate to the aperture ring, and you can see there how limited the dof field is at wide apertures.

You're correct that high shutter spoeeds will force you to use wide apertures, but upping the shutter speed isn't really the best way to go with video and CCD chips. better to use neutral density filters to soak the light.

The f/1.7 lens is approximately 2 stops faster than the f/3.5 lens.

tom.

Tom Hardwick · January 3rd, 2006, 04:38 AM

Yes, the faster lens (the one with the wider aperture) will give shots with more differential focus if used at those wider apertures. Both lenses will give the same dof if used at the same aperture of course.

Most good 35 mm SLR lenses have dof scales that relate to the aperture ring, and you can see there how limited the dof field is at wide apertures.

You're correct that high shutter spoeeds will force you to use wide apertures, but upping the shutter speed isn't really the best way to go with video and CCD chips. better to use neutral density filters to soak the light.

The f/1.7 lens is approximately 2 stops faster than the f/3.5 lens.

tom.

Ben Winter · January 3rd, 2006, 08:12 AM

Keep in mind also that you should practice using the lenses stopped down 1-2 f-stops. Most/all photographics lenses do not produce their best picture quality at maximum aperture. Telephoto/zoom lenses usually need to be stopped down more to gain maximum image quality.

Bob Hart · January 4th, 2006, 12:13 AM

The wider aperture available, the better but if that f3.5 55mm is a Micro-Nikkor, don't throw it away.

You can do some amazing close work with that provided it is not vignetting into the corners of your image. There are some Micro-Nikkor images at www.dvinfo.net/media/hart. Any of the .jpgs with ohara008.JPG or similar filenames were done with this lens.

Brian Valente · January 5th, 2006, 01:24 AM

Quito

IMHO after doing this for a while, getting faster lenses is important for two reasons, but should be tempered.

First, because the whole apparatus combined does lose a fair amount of light. add up the 35mm lens, adapter, and the camera, and you could be a fair amount. The faster the lens, the less issue you have here.

Second, it's true the faster the lens the shallower the depth of field. But check out some of the DOF calculators to see the resulting DOF - you may find yourself shooting with 1" of DOF on a 50mm f1.2 lens. It's great for some applications, but I wouldn't say 1" of DOF is that useful.

A lot of times you'll be wanting to stop down on both the lens (to hit the sweet spot as well as get the DOF relevant for your scene) and also stopping down in the video cam to hit it's sweetspot as well.

January 3rd, 2006, 03:46 AM	#1
Quito Washington Regular Crew Join Date: Dec 2004 Location: Darwin, Australia Posts: 34	50mm 1/1.7 lens vs a 55mm 1/3.5 lens pardon my ignorance but for minimizing depth of field, which would be the better lens? and whats the difference in the two lens anyways, what does the 1.7 or 3.5 refer to exactly? I shot an email to Declan (knowledgable guy that he is) but thought i would open it up to the crowd as well in case anyone had any thoughts... cheers Q __________________ http://www.quitofilms.com brash raw and fully independent

January 3rd, 2006, 04:07 AM	#3
Quito Washington Regular Crew Join Date: Dec 2004 Location: Darwin, Australia Posts: 34	Dof so, according to your post, and to the article, i should use that 1.7 with a high shutter speed to achieve minimum DoF (the least amount in focus)? Q __________________ http://www.quitofilms.com brash raw and fully independent

January 3rd, 2006, 08:12 AM	#6
Ben Winter Trustee Join Date: Jun 2005 Location: Hollywood, CA Posts: 1,675 Images: 1	Keep in mind also that you should practice using the lenses stopped down 1-2 f-stops. Most/all photographics lenses do not produce their best picture quality at maximum aperture. Telephoto/zoom lenses usually need to be stopped down more to gain maximum image quality. __________________ BenWinter.com

January 5th, 2006, 01:24 AM	#8
Brian Valente Major Player Join Date: Jan 2005 Location: Hollywood, CA Posts: 293	Quito IMHO after doing this for a while, getting faster lenses is important for two reasons, but should be tempered. First, because the whole apparatus combined does lose a fair amount of light. add up the 35mm lens, adapter, and the camera, and you could be a fair amount. The faster the lens, the less issue you have here. Second, it's true the faster the lens the shallower the depth of field. But check out some of the DOF calculators to see the resulting DOF - you may find yourself shooting with 1" of DOF on a 50mm f1.2 lens. It's great for some applications, but I wouldn't say 1" of DOF is that useful. A lot of times you'll be wanting to stop down on both the lens (to hit the sweet spot as well as get the DOF relevant for your scene) and also stopping down in the video cam to hit it's sweetspot as well. __________________ ========================== Brian Valente Redrock Microsystems

January 3rd, 2006, 03:58 AM	#2
Carl Jakobsson Regular Crew Join Date: Dec 2005 Location: Lund, Sweden Posts: 122	The values you are refering to is the f-number. Check this out http://en.wikipedia.org/wiki/Aperture A summary: Low f-number=fast lens=big aperture=brighter=less vignetting=shorter DOF=expensive For a 35mm adapter you would probably want a fast lens. 1.7 is "semi"-fast, 1.4 is really fast, and 1.2 is extremely fast. Around 2.0 is mostly standard on SLRs.

January 3rd, 2006, 04:38 AM	#4
Tom Hardwick Inner Circle Join Date: Mar 2003 Location: Billericay, England UK Posts: 4,711	Yes, the faster lens (the one with the wider aperture) will give shots with more differential focus if used at those wider apertures. Both lenses will give the same dof if used at the same aperture of course. Most good 35 mm SLR lenses have dof scales that relate to the aperture ring, and you can see there how limited the dof field is at wide apertures. You're correct that high shutter spoeeds will force you to use wide apertures, but upping the shutter speed isn't really the best way to go with video and CCD chips. better to use neutral density filters to soak the light. The f/1.7 lens is approximately 2 stops faster than the f/3.5 lens. tom.

January 4th, 2006, 12:13 AM	#7
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	The wider aperture available, the better but if that f3.5 55mm is a Micro-Nikkor, don't throw it away. You can do some amazing close work with that provided it is not vignetting into the corners of your image. There are some Micro-Nikkor images at www.dvinfo.net/media/hart. Any of the .jpgs with ohara008.JPG or similar filenames were done with this lens.