Approve the Cookies
This website uses cookies to improve your user experience. By using this site, you agree to our use of cookies. Read More.
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 23 Apr 2008 (Wednesday) 17:57
Search threadPrev/next
sponsored links
(this ad will go away when you log in as a registered member)

Lens dot, what's it for?

 
parsnip
Member
61 posts
Joined Apr 2008
Location: Sheffield
     
Apr 23, 2008 17:57 |  #1

I notice on my 18-55 there's a dot just after 24 on the focal length indicator on the lens. EXIF shows it has 27mm focal length, is there a significance to the dot?


Canon 450D - Canon 18-55 Kit - Canon 70-300 IS USM

  
  LOG IN TO REPLY
sponsored links
(this ad will go away when you log in as a registered member)
Rubberhead
Goldmember
Avatar
1,899 posts
Likes: 1
Joined Feb 2006
Location: South Carolina's Lowcountry
     
Apr 23, 2008 17:58 |  #2

Good question - I've wanted to know about the dot and the flag looking thing too.


EQUIPMENT: 40D | Rebel XT | EF 70-200mm f/4L IS | EF-S 10-22mm | EF 28-135mm IS | EF-S 18-55mm IS | EF 50mm 1.8 - flickr (external link)

  
  LOG IN TO REPLY
Red ­ Dot
Senior Member
Avatar
627 posts
Joined Feb 2008
Location: Trapped Inside the Penta-prism
     
Apr 23, 2008 18:01 |  #3

it indicates where the lens is compacted most. at 55 it extends, and at the dot it is smalles. the flag is usually when the compactness is achieved at the end of the focal range.


I tried to write my signature, but my pen ran out and I put a big scratch on my monitor

  
  LOG IN TO REPLY
cito17
Senior Member
Avatar
724 posts
Likes: 19
Joined Feb 2008
Location: SF Bay Area
     
Apr 23, 2008 18:01 as a reply to  @ Rubberhead's post |  #4

I looked on mine and it's the spot were the lens is most retracted.


-Adrian [ Flickr ] (external link)[ Tumblr. ] (external link)[Full Gear List]
[ EOS 5D III|EOS 30D|Canonet QL17 G-III|Olympus OM-1|Rolleiflex MX-EVS|Leica M2 ]

  
  LOG IN TO REPLY
parsnip
THREAD ­ STARTER
Member
61 posts
Joined Apr 2008
Location: Sheffield
     
Apr 23, 2008 18:04 as a reply to  @ cito17's post |  #5

yeah the flag is the beginning of the focal range on mine so it indicates 18

Mine isn't most retracted at the dot though, it's most around 30


Canon 450D - Canon 18-55 Kit - Canon 70-300 IS USM

  
  LOG IN TO REPLY
parsnip
THREAD ­ STARTER
Member
61 posts
Joined Apr 2008
Location: Sheffield
     
Apr 24, 2008 07:11 as a reply to  @ parsnip's post |  #6

I just read a review saying 28 mm is the most common wide angle focal length, could this be a 28mm indicator?


Canon 450D - Canon 18-55 Kit - Canon 70-300 IS USM

  
  LOG IN TO REPLY
Rankinia
Senior Member
449 posts
Joined Mar 2008
Location: Sydney, Australia
     
Apr 24, 2008 09:12 |  #7

28mm is a lovely focal length, but that is the equivalent for an ef-s lens is approx 17mm if i remember right.

Adam


1ds, 30d, 17-40/4 180/3.5, mt-24, 580ex2
http://adamrose.wordpr​ess.com (external link)

  
  LOG IN TO REPLY
timnosenzo
Cream of the Crop
8,831 posts
Likes: 10
Joined Sep 2005
Location: CT
     
Apr 24, 2008 10:01 |  #8

parsnip wrote in post #5393755 (external link)
I just read a review saying 28 mm is the most common wide angle focal length, could this be a 28mm indicator?

This would be my guess. My 24-105 has a dot at what looks to be 28, but its most retracted at 24.


connecticut wedding photographer (external link)

  
  LOG IN TO REPLY
Stocky
Senior Member
Avatar
722 posts
Joined Feb 2008
Location: Boston, MA
     
Apr 24, 2008 10:49 |  #9

I agree that its the (approximate) spot where the lens is its shortest physical length. I also realized that I don't have a manual for that lens. Apparently the kit didn't come with one. Unfortunately this is my only zoom lens (1 going on 5), but I see from pictures that the 24-70 and 17-55 both have the flags on them and the 24-70 has a dot as well (right next to the flag at the short end of the focal length). The 70-200 series do not seem to have any of these markings. I will be very interested to hear an explanation for all of this if there is one.


Always happy to hear some critique
gear list

  
  LOG IN TO REPLY
parsnip
THREAD ­ STARTER
Member
61 posts
Joined Apr 2008
Location: Sheffield
     
Apr 24, 2008 15:10 |  #10

Rankinia wrote in post #5394296 (external link)
28mm is a lovely focal length, but that is the equivalent for an ef-s lens is approx 17mm if i remember right.

Adam

That's true due to the 1.6 factor, it's about 17.5mm on an XSI although I guess the factor is camera dependent. So the dot may be more useful on a full frame camera

Either way the theory it is the shortest physical lengths doesnt seem to work across lenses, plus when you contract the lens focusing also affects the length


Canon 450D - Canon 18-55 Kit - Canon 70-300 IS USM

  
  LOG IN TO REPLY
msowsun
Cream of the Crop
Avatar
9,203 posts
Gallery: 14 photos
Best ofs: 1
Likes: 226
Joined Jul 2007
Location: Oakville Ont. Canada
     
Apr 24, 2008 16:32 |  #11

parsnip wrote in post #5396257 (external link)
Either way the theory it is the shortest physical lengths doesnt seem to work across lenses, plus when you contract the lens focusing also affects the length

My Sigma 17-70 also has a white dot just between the 24 and 35. This lens only gets longer as it zooms out from 17 to 70. (the shortest physical length is at 17)


Mike Sowsun / S110 / SL1 / 80D / EF-S 24mm STM / EF-S 10-18mm STM / EF-S 18-55mm STM / EF-S 18-135mm STM / EF-S 18-135mm USM / EF-S 55-250mm STM / 5D3 / Samyang 14mm 2.8 / EF 40mm 2.8 STM / EF 50mm 1.8 STM / EF 100mm 2.0 USM / EF 100mm 2.8 USM Macro / EF 24-105mm IS / EF 70-200mm 2.8L IS Mk II / EF 1.4x II
Full Current and Previously Owned Gear List over 40 years Flickr Photostream (external link)

  
  LOG IN TO REPLY
Chandler.
Goldmember
Avatar
2,781 posts
Likes: 1
Joined Dec 2006
Location: Issaquah
     
Apr 24, 2008 16:42 |  #12

Stocky wrote in post #5394790 (external link)
I agree that its the (approximate) spot where the lens is its shortest physical length.... I see from pictures that the 24-70 and 17-55 both have the flags on them and the 24-70 has a dot as well (right next to the flag at the short end of the focal length). The 70-200 series do not seem to have any of these markings. I will be very interested to hear an explanation for all of this if there is one.

The 24-70L does not have any flag or dot markings. Besides, it's a reverse zoom lens and is longest at 24mm, and shortest at 70mm.

The 70-200Ls are all internal focus lenses, so they wouldn't need a dot to determine the shortest physical length.


There are no rules for good photographs, there are only good photographs. ~ Ansel Adams

  
  LOG IN TO REPLY
20droger
Cream of the Crop
14,685 posts
Likes: 25
Joined Dec 2006
     
Apr 24, 2008 17:04 |  #13

parsnip wrote in post #5390489 (external link)
I notice on my 18-55 there's a dot just after 24 on the focal length indicator on the lens. EXIF shows it has 27mm focal length, is there a significance to the dot?

For the 18-55mm lens, the dot represents "28" on the focal-length scale. That means the scale reads "18 24 [28] 35 55". Even though the 28mm position has no real significance for an EF-S lens, it is still a very popular size, historically.

The lens instruction sheet came with our camera-lens kit, but does not specifically say anything about the dot. When I carefull set the lens to the dot, the measured focal length (on our lens) is 27.6mm. This lens has very high tolerances, however, and I would not be surprised at anything between 26mm and 30mm.

On the EF 28-135mm f/3.5-5.6 IS USM lens, there is a little "flag" just left of the 35mm marking, between the numbers "28" and "35". This flag is really a square dot indicating the position of 28mm, with a small line extending to the number "28".

These dots and similar tricks are used on some lenses to include numbers that simply will not fit, as numbers, in their proper positions. These dots or "flags" have absolutely nothing to do with the extension of the lens.

Hope this helps.




  
  LOG IN TO REPLY
parsnip
THREAD ­ STARTER
Member
61 posts
Joined Apr 2008
Location: Sheffield
     
Apr 24, 2008 17:27 |  #14

20droger was correct about the dot

Official canon response...

"The dot on the lens shows where 28mm is located."


Canon 450D - Canon 18-55 Kit - Canon 70-300 IS USM

  
  LOG IN TO REPLY
number ­ six
"After 40 years still not housebroken, I still piddle on the carpet"
Avatar
8,906 posts
Likes: 36
Joined May 2007
Location: SF Bay Area
     
Apr 24, 2008 19:22 |  #15

parsnip wrote in post #5397194 (external link)
20droger was correct about the dot

Official canon response...

"The dot on the lens shows where 28mm is located."

And why do we care? Because 28 mm is the "normal" focal length on a 1.6 crop camera?

That's what I've been assuming...

-js


"Be seeing you."
50D - 17-55 f/2.8 IS - 18-55 IS - 28-105 II USM - 60 f/2.8 macro - 70-200 f/4 L - Sigma flash
I do not piddle on the carpet!

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

3,459 views & 1 like for this thread
Lens dot, what's it for?
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?
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 2.0forum software
version 2.0 /
code and design
by Pekka Saarinen ©
for photography-on-the.net

Latest registered member is henkbriek
738 guests, 265 members online
Simultaneous users record so far is 6430, that happened on Dec 03, 2017

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.