Approve the Cookies
This website uses cookies to improve your user experience. By using this site, you agree to our use of cookies and our Privacy Policy.
OK
Index  •   • New posts  •   • RTAT  •   • 'Best of'  •   • Gallery  •   • Gear  •   • Reviews
Guest
New posts  •   • RTAT  •   • 'Best of'  •   • Gallery  •   • Gear  •   • Reviews
Register to forums    Log in

 
FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 15 Aug 2012 (Wednesday) 19:19
Search threadPrev/next
sponsored links
(this ad will go away when you log in as a registered member)

Minimum focusing distance and focal length....help

 
Ursie
Senior Member
Avatar
529 posts
Likes: 52
Joined May 2007
Location: Vail, AZ
     
Aug 15, 2012 19:19 |  #1

I am not a technical girl so I'm hoping one of you technical folks can help me determine the answer.

If a 100mm macro lens has a minimum focusing distance of .9 ft and a 70-300 macro capable lens has a minimum focusing distance of 37.4 inches, is it true to say that you will effectively get a higher magnification of a given image when using the 100mm at minimum focusing distance?

Basically, I'm trying to determine exactly what I will gain if I purchase a 100mm vs my 70-300 (which captures some pretty wonderful images). Will I gain in actual magnification?


Gear List
My Gallery (external link)
My Blog (external link)

  
  LOG IN TO REPLY
sponsored links
(this ad will go away when you log in as a registered member)
Wilt
Reader's Digest Condensed version of War and Peace [POTN Vol 1]
Avatar
41,908 posts
Gallery: 1 photo
Likes: 2616
Joined Aug 2005
Location: Belmont, CA
     
Aug 15, 2012 19:32 |  #2

70mm at 37.4" yields a 0.079x magnification; 100mm at 37.4" yields 0.12x magnification; 300mm at 37.4" yields 0.46x magnification.

100mm at 10.8" (0.9 ft) yields 0.57x magnification; the 100mm macro is the better lens for magnification.


You need to give me OK to edit your image and repost! Keep POTN alive and well with member support https://photography-on-the.net/forum/donate.p​hp
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention

  
  LOG IN TO REPLY
Ursie
THREAD ­ STARTER
Senior Member
Avatar
529 posts
Likes: 52
Joined May 2007
Location: Vail, AZ
     
Aug 15, 2012 19:34 |  #3

thank you Wilt! I knew there'd be a genius who could give me that answer.


Gear List
My Gallery (external link)
My Blog (external link)

  
  LOG IN TO REPLY
SkipD
Cream of the Crop
Avatar
20,476 posts
Likes: 159
Joined Dec 2002
Location: Southeastern WI, USA
     
Aug 15, 2012 19:38 |  #4

There's another issue to consider, though, and that's the perspective in the images. Composition might be better with the 300mm lens at 38 inches than the 100mm lens at a bit more than a foot. In other words, there may be more than just magnification to choose from when photographing three-dimensional subjects.

Please read our "sticky" (found in the General Photography Talk forum) tutorial titled Perspective Control in Images - Focal Length or Distance?.


Skip Douglas
A few cameras and over 50 years behind them .....
..... but still learning all the time.

  
  LOG IN TO REPLY
gtrag94
Senior Member
273 posts
Likes: 1
Joined Aug 2011
Location: Fort Wayne, IN
     
Aug 15, 2012 19:41 |  #5

100mm MACRO at 0.9ft (minimum focusing distance) yields 1.0x magnification, not .57x. It is indeed a true macro lens which, by definition yields 1.0x magnification (life size). The exception is the 50mm compact macro which is half life size (or .5x magnification). A zoom lens that has "macro" stamped on it doesn't make it compare to a true macro lens. It is more of a marketing gimmick that means the lens focuses reasonably close.

That said, most people don't need a true macro lens as they get incredibly close. I'd recommend renting one to see if you need that capability. They're fun, and double as super sharp portrait lenses because they're usually fast and of portrait length.


Fort Wayne, IN Portrait & Wedding Photographer
http://www.craigagapie​photography.com (external link)
http://www.facebook.co​m/CraigAgapiePhotograp​hy (external link)

  
  LOG IN TO REPLY
Wilt
Reader's Digest Condensed version of War and Peace [POTN Vol 1]
Avatar
41,908 posts
Gallery: 1 photo
Likes: 2616
Joined Aug 2005
Location: Belmont, CA
     
Aug 15, 2012 19:48 |  #6

gtrag94 wrote in post #14863697 (external link)
100mm MACRO at 0.9ft (minimum focusing distance) yields 1.0x magnification, not .57x. It is indeed a true macro lens which, by definition yields 1.0x magnification (life size). The exception is the 50mm compact macro which is half life size (or .5x magnification). A zoom lens that has "macro" stamped on it doesn't make it compare to a true macro lens. It is more of a marketing gimmick that means the lens focuses reasonably close.

As is true of a number of Canon macro lenses, Canon moves some of the internal optics so that the FL is NOT truly 100mm any longer, so that the optics can achieve a certain magnfication!
Per the lens specifications, the 100mm f/2.8L lens actually focuses to a minimum of 0.99' to achieve 1x reproduction. The 100mm f/2.8 non-L lens focuses to 1' minimum yet also achieves 1x reproduction that that slightly longer distance...evidence of the internal games with actual FL.

Oops, the calculator which I was using was for lens' Optical Center to focal plane!


You need to give me OK to edit your image and repost! Keep POTN alive and well with member support https://photography-on-the.net/forum/donate.p​hp
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention

  
  LOG IN TO REPLY
Wilt
Reader's Digest Condensed version of War and Peace [POTN Vol 1]
Avatar
41,908 posts
Gallery: 1 photo
Likes: 2616
Joined Aug 2005
Location: Belmont, CA
     
Aug 15, 2012 20:36 |  #7

OK, found another macro calculator, and this one uses focus distance!

70mm at 37.4" yields a 0.09x magnification; 100mm at 37.4" yields 0.14x magnification; 300mm at 37.4" yields 1.0x magnification.

The difference between the 100mm macro and the 300mm would not only be the amount of working distance (distance between lens and subject) but the longer FL is likely to provide more blur of objects in the background.


You need to give me OK to edit your image and repost! Keep POTN alive and well with member support https://photography-on-the.net/forum/donate.p​hp
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention

  
  LOG IN TO REPLY
1Tanker
Goldmember
Avatar
4,470 posts
Likes: 5
Joined Jan 2011
Location: Swaying to the Symphony of Destruction
     
Aug 15, 2012 20:47 |  #8

Wilt wrote in post #14863909 (external link)
OK, found another macro calculator, and this one uses focus distance!

70mm at 37.4" yields a 0.09x magnification; 100mm at 37.4" yields 0.14x magnification; 300mm at 37.4" yields 1.0x magnification.

The difference between the 100mm macro and the 300mm would not only be the amount of working distance (distance between lens and subject) but the longer FL is likely to provide more blur of objects in the background.

True, but the shallower DoF, due to being closer with the 100, should pretty-much even that out..correct?


Kel
Gear

  
  LOG IN TO REPLY
Wilt
Reader's Digest Condensed version of War and Peace [POTN Vol 1]
Avatar
41,908 posts
Gallery: 1 photo
Likes: 2616
Joined Aug 2005
Location: Belmont, CA
     
Aug 15, 2012 22:11 |  #9

1Tanker wrote in post #14863935 (external link)
True, but the shallower DoF, due to being closer with the 100, should pretty-much even that out..correct?

Not correct...The same ultimate size of the subject in the frame results in same DOF!

100mm at 11.8"/0.3m focus distance at f/11 has 0.083" DOF zone, while 300mm at 0.9m/35.4" at f/11 also has 0.083" DOF zone.


You need to give me OK to edit your image and repost! Keep POTN alive and well with member support https://photography-on-the.net/forum/donate.p​hp
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention

  
  LOG IN TO REPLY
1Tanker
Goldmember
Avatar
4,470 posts
Likes: 5
Joined Jan 2011
Location: Swaying to the Symphony of Destruction
     
Aug 15, 2012 22:25 |  #10

Wilt wrote in post #14864198 (external link)
Not correct...The same ultimate size of the subject in the frame results in same DOF!

100mm at 11.8"/0.3m focus distance at f/11 has 0.083" DOF zone, while 300mm at 0.9m/35.4" at f/11 also has 0.083" DOF zone.

Ok.. but plug in 37.4", not 35.4". ;)


Kel
Gear

  
  LOG IN TO REPLY
jimewall
Goldmember
1,871 posts
Likes: 11
Joined May 2008
Location: Cleveland, Ohio
     
Aug 15, 2012 22:30 |  #11

Wilt wrote in post #14863909 (external link)
.... but the longer FL is likely to provide more blur of objects in the background.

Technically this is not correct either.

With a subject framed the same with the same aperture (say 1 to 1), the longer focal length causes the a narrower FOV and thus magnifies the background more (than a wider FL). Because of this the background of the longer FL appears like there is more blur (out of focus) areas but technically there is the same amount of blur. It is just not enlarged as much with the wider FL, so looks choppier and not as smooth (compared to the longer FL).

But this does mean usually the longer FL makes for a more pleasing picture, because of the smoother look due to the greater magnification of the OOF background. It would be what most people would call greater blur, but they are technically wrong (but they did get the effect they desired).


Thanks for Reading & Good Luck - Jim
GEAR

  
  LOG IN TO REPLY
Wilt
Reader's Digest Condensed version of War and Peace [POTN Vol 1]
Avatar
41,908 posts
Gallery: 1 photo
Likes: 2616
Joined Aug 2005
Location: Belmont, CA
     
Aug 15, 2012 22:33 |  #12

1Tanker wrote in post #14864243 (external link)
Ok.. but plug in 37.4", not 35.4". ;)

I was not using the OP distances, I merely started with 0.3m and the shorter FL, then multiplied both the focus distance and the FL by 3x to keep the subject size the same on sensor.
If I started with 35.4"/0.9m at 100mm, I would use 106.29"/2.7m for 300mm, and have the same DOF range for both lenses.


You need to give me OK to edit your image and repost! Keep POTN alive and well with member support https://photography-on-the.net/forum/donate.p​hp
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention

  
  LOG IN TO REPLY
1Tanker
Goldmember
Avatar
4,470 posts
Likes: 5
Joined Jan 2011
Location: Swaying to the Symphony of Destruction
     
Aug 15, 2012 22:41 as a reply to  @ Wilt's post |  #13

I used 11.8" for the 100, and 37.4" for the 300, on DOFMaster, and while the difference seems small(.12" for 300, .1" for 100), it's still 20% shallower DOF with the 100.. both lenses shot at MFD.


Kel
Gear

  
  LOG IN TO REPLY
Wilt
Reader's Digest Condensed version of War and Peace [POTN Vol 1]
Avatar
41,908 posts
Gallery: 1 photo
Likes: 2616
Joined Aug 2005
Location: Belmont, CA
     
Aug 15, 2012 22:54 |  #14

jimewall wrote in post #14864263 (external link)
Technically this is not correct either.

With a subject framed the same with the same aperture (say 1 to 1), the longer focal length causes the a narrower FOV and thus magnifies the background more (than a wider FL). Because of this the background of the longer FL appears like there is more blur (out of focus) areas but technically there is the same amount of blur. It is just not enlarged as much with the wider FL, so looks choppier and not as smooth (compared to the longer FL).

But this does mean usually the longer FL makes for a more pleasing picture, because of the smoother look due to the greater magnification of the OOF background. It would be what most people would call greater blur, but they are technically wrong (but they did get the effect they desired).

http://www.zeiss.com …/$File/CLN35_Bo​keh_en.pdf (external link)

Zeiss clearly states, "the infinitely distant background is displayed with a different amount of blurriness because the entrance pupils are different...the bundles of light entering from the infinite distance into the entrance pupils intersect the object plain in different areas. That is why the blurriness in the image is not the same for very distant objects. " Regarding the size of the circle of confusion, "in the far distant background the influence of focal length predominates...The decisive parameter for the quantity of the blurriness is therefore the physical size of the entrance pupil", the diameter of the opening (not the f/number). 300mm f/11 would have entrance pupil of 27.27mm while 100mm f/11 has entrance pupil of 9.09mm, so the distance background is more blurred because of the size of the circles of confusion.
"


You need to give me OK to edit your image and repost! Keep POTN alive and well with member support https://photography-on-the.net/forum/donate.p​hp
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention

  
  LOG IN TO REPLY
Ursie
THREAD ­ STARTER
Senior Member
Avatar
529 posts
Likes: 52
Joined May 2007
Location: Vail, AZ
     
Aug 16, 2012 09:49 |  #15

So if I am understanding correctly, I can get the same amount of magnification from either lens technically. I am interested in great magnification than that.

Do most macro photogs add extender tubes and such to get the super macro look?


Gear List
My Gallery (external link)
My Blog (external link)

  
  LOG IN TO REPLY
sponsored links
(this ad will go away when you log in as a registered member)

3,591 views & 0 likes for this thread
Minimum focusing distance and focal length....help
FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
AAA
x 1600
y 1600

Jump to forum...   •  Rules   •  Index   •  New posts   •  RTAT   •  'Best of'   •  Gallery   •  Gear   •  Reviews   •  Member list   •  Polls   •  Image rules   •  Search   •  Password reset

Not a member yet?
Register to forums
Registered members may log in to forums and access all the features: full search, image upload, follow forums, own gear list and ratings, likes, more forums, private messaging, thread follow, notifications, own gallery, all settings, view hosted photos, own reviews, see more and do more... and all is free. Don't be a stranger - register now and start posting!


COOKIES DISCLAIMER: This website uses cookies to improve your user experience. By using this site, you agree to our use of cookies and to our privacy policy.
Privacy policy and cookie usage info.


POWERED BY AMASS forum software 2.1forum software
version 2.1 /
code and design
by Pekka Saarinen ©
for photography-on-the.net

Latest registered member is Willday
993 guests, 298 members online
Simultaneous users record so far is 15144, that happened on Nov 22, 2018

Photography-on-the.net Digital Photography Forums is the website for photographers and all who love great photos, camera and post processing techniques, gear talk, discussion and sharing. Professionals, hobbyists, newbies and those who don't even own a camera -- all are welcome regardless of skill, favourite brand, gear, gender or age. Registering and usage is free.