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

Go Back   DV Info Net > Special Interest Areas > Alternative Imaging Methods

Alternative Imaging Methods
DV Info Net is the birthplace of all 35mm adapters.


Reply
 
Thread Tools Search this Thread
Old January 3rd, 2006, 03:46 AM   #1
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
Quito Washington is offline   Reply With Quote
Old January 3rd, 2006, 03:58 AM   #2
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.
Carl Jakobsson is offline   Reply With Quote
Old January 3rd, 2006, 04:07 AM   #3
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
Quito Washington is offline   Reply With Quote
Old January 3rd, 2006, 04:38 AM   #4
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.
Tom Hardwick is offline   Reply With Quote
Old January 3rd, 2006, 04:38 AM   #5
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.
Tom Hardwick is offline   Reply With Quote
Old January 3rd, 2006, 08:12 AM   #6
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
Ben Winter is offline   Reply With Quote
Old January 4th, 2006, 12:13 AM   #7
Inner Circle
 
Join Date: Dec 2003
Location: PERTH. W.A. AUSTRALIA.
Posts: 4,356
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.
Bob Hart is offline   Reply With Quote
Old January 5th, 2006, 01:24 AM   #8
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
Brian Valente is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Special Interest Areas > Alternative Imaging Methods

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 10:42 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network