Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-22-2011, 10:11 AM   #1
Pentaxian
littledrawe's Avatar

Join Date: Jan 2010
Location: Red Rock
Photos: Gallery | Albums
Posts: 2,434
focal length on crop sensor question?

Would a lens made for the the pentax film SLR with a focal length of 35-135 be the equivalent of the DA 50-200 currently produced if the crop factor is applied to the older lens?

09-22-2011, 10:23 AM   #2
Veteran Member




Join Date: May 2009
Location: Twin Cities, MN
Posts: 2,869
If you're asking if they'll be the same, the answer is no. I think you might have it mixed up a little. The 35-135mm will have an approximate field of view of 50-200mm in 35mm terms when used with the APS-C sensors in Pentax DSLRs. The 50-200mm used on APS-C DSLRs has a 35mm film equivalent field of view of 100-300mm.
09-22-2011, 10:31 AM   #3
Loyal Site Supporter
eddie1960's Avatar

Join Date: Aug 2010
Location: Toronto
Photos: Gallery | Albums
Posts: 12,165
Crop factor is very decptive.
it's about FOV
the 35-135 length when used on apsc provides and approximate field of view of 52.5-202.5 used on 35mm
a 50-200 is still a longer lens on apsc than the 35-135
the focal length of a lens is the same regardless of format, crop factor was a way for old guys who shot 35mm (like me) to estimate how their lenses would look on the crop sensor.
the DA50-200 cannot be used on film bodies do to a smaller image circle since it was designed to cover the smaller sensor, but it's apsc crop factor equivalent would be like a 75-300 on 35mm

That being
09-22-2011, 10:31 AM   #4
Loyal Site Supporter
eddie1960's Avatar

Join Date: Aug 2010
Location: Toronto
Photos: Gallery | Albums
Posts: 12,165
QuoteOriginally posted by pxpaulx Quote
If you're asking if they'll be the same, the answer is no. I think you might have it mixed up a little. The 35-135mm will have an approximate field of view of 50-200mm in 35mm terms when used with the APS-C sensors in Pentax DSLRs. The 50-200mm used on APS-C DSLRs has a 35mm film equivalent field of view of 100-300mm.
75-300 (factor 1.5)

09-22-2011, 11:49 AM   #5
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
QuoteOriginally posted by littledrawe Quote
Would a lens made for the the pentax film SLR with a focal length of 35-135 be the equivalent of the DA 50-200 currently produced if the crop factor is applied to the older lens?
Moving a lens to a different camera does not change its focal length. Moving a lens to a camera with a smaller frame (film or digital) crops a smaller portion of the projected image, hence the term crop-sensor. Moving a lens to a camera with a larger frame records a larger portion of the projected image. The frame size determines the FOV produced by by any given focal length.

An 18-55mm lens on APS-C has equivalent FOV as a 28-80mm lens on 135/FF.
A 35-135mm lens on APS-C has equivalent FOV as a 50-200mm lens on 135/FF.

Unless you're an experienced 135/FF photographer who is transitioning to APS-C or 135/HF, forget that you ever heard of crap.factor. Just use your lenses and learn what each focal length does on each camera. Back in the day, I sometimes shot 135/HF and 135/FF and 6x6/MF and 9x12/MF on the same day, sometimes with the same lens. My colleagues and I never referred to crap.factor; the term hadn't yet been invented by a marketing wonk. We just learned our lenses. It ain't hard.
09-22-2011, 12:17 PM   #6
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
back to basics.

Focal length is focal length. it is a physical characteristic of a lens, speccifically measured when the lens is set to infinity. Basically, for s single lens it is the distance from the lens to the focusing plane, such that parallel light striking the lens focuses at a point.

It gets a little more complex when you talk about compound (multiple element lenses) which is where the field of view comes in. Field of view usually measured across the diagonal of a frame, relates to an effective focal length for any one format.

As Rio said forget you ever heard about crop factor. any interchangeable lens is marked with its focal length with no inference to format that it gets put on.

It is only when you look at P&S cameras, that crop factor gets introduced because almost every P&S has a different sized chip, so to make it relitively simple to compare cameras, it seems everyone has adapted an equivelent to 35mm focal length, (based upon the FOV of the lens on the sensor) as if the other formats simply don't exist.
09-22-2011, 12:44 PM   #7
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
here's a hopefully simple way of looking at it:

Crop factor is comparing *cameras*, not for comparing *lenses*. It doesn't matter who made the 35-105 or when or what kind of camera they made it for. A 35-105 lens is shorter (wider field of FOV) than a 50-200 lens when both are mounted to the same camer. Period, end of story. However, if you mount that 35-105 to a film / FF camera, it will indeed have a different FOV than it does on a crop camera, and yeah, 35-135 on a FF body is kind of sort of like 50-200 on a crop camera. But it's the camera that does this, not the lens. Again, if both lenses are mounted to the same camera, the 50-200 is longer, every time.
09-22-2011, 03:42 PM   #8
Pentaxian
littledrawe's Avatar

Join Date: Jan 2010
Location: Red Rock
Photos: Gallery | Albums
Posts: 2,434
Original Poster
QuoteOriginally posted by RioRico Quote
forget that you ever heard of crap.factor.
Thank you sir! I didn't want to get too wrapped up in it, I just wanted to see if my thinking is correct. Thanks for the help everyone!

09-22-2011, 04:15 PM   #9
Senior Moderator
Loyal Site Supporter
Parallax's Avatar

Join Date: Apr 2008
Location: South Dakota
Photos: Gallery
Posts: 15,104
QuoteOriginally posted by littledrawe Quote
I didn't want to get too wrapped up in it, ....
You just gave yourself better advice than any of us could give you. If you can't see enough, use a shorter lens. If you want a closer look, use a longer one. Quit worrying about how things compare.
09-23-2011, 05:38 AM   #10
Veteran Member
Squier's Avatar

Join Date: Apr 2009
Location: Oxfordshire UK
Photos: Albums
Posts: 707
QuoteOriginally posted by littledrawe Quote
Thank you sir! I didn't want to get too wrapped up in it, I just wanted to see if my thinking is correct. Thanks for the help everyone!
Quite right - and due to good advice here, you can now ignore everyone and his brother, and lens retailers too, ( who should know better but have jumped on the ' crop ' bandwagon ) when they tell you / or advertise a 500mm lens having a focal length of 750mm when you pop the lens on a 1.5x crop camera
09-23-2011, 08:56 AM   #11
Veteran Member




Join Date: May 2009
Location: Twin Cities, MN
Posts: 2,869
QuoteOriginally posted by eddie1960 Quote
75-300 (factor 1.5)
Thats what happens when you use Pentax along with a couple of micro 4/3 cameras, your brain turns to mush! hahaha.
09-23-2011, 11:08 AM   #12
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
Wait wait, I have a solution! Yes, there IS magic in the world! Yes, lenses DO change their focal lengths spontaneously! You might ask: How, how can this happen? The answer is simple: FASTER-THAN-LIGHT NEUTRINOS!! Yes, putting a lens on a different camera distorts the local space-time fabric and allows neutrinos (and the photons they drag along with them) to wormhole through the optics at FTL speeds! And *I* discovered this!! Where's my Nobel??
09-24-2011, 11:44 PM   #13
Pentaxian
littledrawe's Avatar

Join Date: Jan 2010
Location: Red Rock
Photos: Gallery | Albums
Posts: 2,434
Original Poster
QuoteOriginally posted by RioRico Quote
Where's my Nobel??
You've got my vote!!!
09-25-2011, 09:29 AM   #14
Senior Member




Join Date: Oct 2009
Location: ita/swiss
Posts: 270
QuoteOriginally posted by littledrawe Quote
You've got my vote!!!
I sent many pm, if you answer me do me a favor :ugh:
09-28-2011, 03:06 AM - 1 Like   #15
Veteran Member
DaveHolmes's Avatar

Join Date: Jul 2010
Location: Yorkshire
Posts: 1,501
QuoteOriginally posted by Parallax Quote
If you want a closer look, use a longer one. Quit worrying about how things compare.
And if you only have one lens to go at... Walk forwards and/or backwards
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, crop, crop sensor, length, lens, pentax help, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Crop Factor, Focal Length and Field of View Ole Pentax Lens Articles 15 05-26-2013 12:41 PM
FFF question - fisheye, focal length and FOV d.bradley Pentax SLR Lens Discussion 10 09-11-2011 11:21 PM
Manual lenses and Focal length prompt question. Al_T Troubleshooting and Beginner Help 15 11-10-2010 11:14 AM
Focal length question McLovin Pentax SLR Lens Discussion 5 09-17-2009 12:49 PM
FA Limited Lens' focal length question VAV Pentax SLR Lens Discussion 36 08-09-2008 04:34 PM



All times are GMT -7. The time now is 01:35 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top