cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

DSLR 101 3.0

jazzman1
Rising Star

 

 

 

1 ACCEPTED SOLUTION

jrhoffman75
Legend
Unless there is only one item in your viewfinder, which is next to impossible, there are an infinite number of distances between you and the items.

Only one distance is in perfect focus, and depending on depth of field, a range of distances will be in acceptable focus.

Zooming the lens doesn't change the distance anymore than it compresses the distance between objects.

Maybe it's my imagination, but I often feel a tugging on my leg when I read some of these postings.
John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic

View solution in original post

44 REPLIES 44

Those numbers you're throwing around are the focal lengths (in millimeters) of the lenses you're using. They have nothing directly to do with the distance from the camera to the subject - in yards, feet, meters, rods, fathoms, furlongs, or any other units. Where on earth did you get the idea that they do? I hope it wasn't from me or Ernie.

 

If what you're doing is trying to calculate the depth of field for various distances and focal lengths, there are tables for that. I don't refer to them much, but I believe the camera-to-subject distances are usually quoted in feet.

Bob
Philadelphia, Pennsylvania USA


@RobertTheFat wrote:

Those numbers you're throwing around are the focal lengths (in millimeters) of the lenses you're using. They have nothing directly to do with the distance from the camera to the subject - in yards, feet, meters, rods, fathoms, furlongs, or any other units. Where on earth did you get the idea that they do? I hope it wasn't from me or Ernie.

 

If what you're doing is trying to calculate the depth of field for various distances and focal lengths, there are tables for that. I don't refer to them much, but I believe the camera-to-subject distances are usually quoted in feet.


I'm trying to figure the actual distance from an object I'm shooting.  As in one of the pics I posted of the jazz fest of the band on stage.  Whenever I shoot at a distance, just a example, a tree, that may in my opinion be 100 yds away in real distance.  My lens only shows distance in mm.   Maybe I'm wrong here, maybe it's non issue I should'nt worry about, I don't know.  It's just something I would like to know, how fto determine how far away from whatever I'm shooting is in ft. and yds.  I've looked at what the lens says in mm when I zoom in but that's no help.  I guess maybe you guys never understood the question.   Sorry if I was'nt plain.

 

BTW...Nobody told me any of the stuff you mentioned, nor have I asked that, or wanted to know.  I think this question of mm has been an issue of mis-communication...between us all.   I don't think you guys understood my question, so your answers did'nt appy for me.  If so, I'm very sorry keeping this running so long.  Actually it seems like a very simple question with an easy answer.  But maybe i'm wrong about that.

 

 

 
Re: DSLR 101 3.0
 

@RobertTheFat wrote:

Those numbers you're throwing around are the focal lengths (in millimeters) of the lenses you're using. They have nothing directly to do with the distance from the camera to the subject - in yards, feet, meters, rods, fathoms, furlongs, or any other units

 

I know this Bob....the mm reading on my lens tells me nothing about my distance from my camera to a subject or scene.....far away.  That's why this question.   I'm mostly trying to know the actual distance from my camera when taking a shot.  The question came to mind when I saw gear called "range finders".   So I thought those may be helpful to learn distance when taking long range shots.  My thinking is knowing our distance, say 100 yrs.....may be helpful in getting the right camera settings for the shot.   And those settings might change depending on the light.  I'm thinking knowing my distance for any given shot, would help determine the best settings, of my camera to use, for that shot.

 

Maybe this is a nonsense question, if so, I'm very sorry to have bothered you and Biggs with it.

jrhoffman75
Legend
Unless there is only one item in your viewfinder, which is next to impossible, there are an infinite number of distances between you and the items.

Only one distance is in perfect focus, and depending on depth of field, a range of distances will be in acceptable focus.

Zooming the lens doesn't change the distance anymore than it compresses the distance between objects.

Maybe it's my imagination, but I often feel a tugging on my leg when I read some of these postings.
John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic


@jrhoffman75 wrote:
Unless there is only one item in your viewfinder, which is next to impossible, there are an infinite number of distances between you and the items.

Only one distance is in perfect focus, and depending on depth of field, a range of distances will be in acceptable focus.

Zooming the lens doesn't change the distance anymore than it compresses the distance between objects.

Maybe it's my imagination, but I often feel a tugging on my leg when I read some of these postings.

Hey jrhoffman75.  Thanks for the help and this does help.  Guess you're saying my distance should not be an issue in taking any of my shots.  That's good to know, I feel a little relief.  Bugs me to no end when there's something I think I should know and can't figure the answer. 

-   -----    -----     -------     ------     --------      --------

 

I often feel a tugging on my leg when I read some of these postings

 

Guess you mean you help lost causes, stray dogs, and newbies like me (LOL)

 

BTW.....Thanks much.

"... depending on depth of field, a range of distances will be in acceptable focus."

 

This called the hyperfocal distance. It is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp.

EB
EOS 1DX and 1D Mk IV and several lenses!


@ebiggs1 wrote:

"... depending on depth of field, a range of distances will be in acceptable focus."

 

This called the hyperfocal distance. It is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp.


A "range of distance" for accpetable focus is just "depth of field".  "Hyperfocal distance" is a slightly different concept.  

 

For any given lens focal length and aperture value, there is a focus distance which will maximize the depth of field.  That magic value which maximizes depth of field (just for that specific focal length and aperture value) is the "hyperfocal distance".  Any other value may achieve a very broad depth of field, though not necessarily the most broad depth of field possible.

 

Every lens focal length, focused distance, and aperture value combination has a "depth of field" -- but it's not necessarily the "hyperfocal distance".

 

A new photographer might think that to maximize depth of field they could just focus the lens to infinity and use a high aperture value, like this:

 

Infinity.jpg

 

The above camera lens is set to f/22 (which should generate a broad depth of field) and it is focused to "infinity".  If you look at the blue boxed area that I've annotated, this shows the range of distances at which your subjects should be in acceptable focus.  It looks like everything from about 12' to "infinity" will be in focus.  

 

The problem with this is that it wastes some depth of field.  Because the lens is "also" focusing a range of distances which are "beyond infinity" and since nothing can be "beyond infinity" we really just lose the benefit of that range.

 

So to achieve a true "hyperfocal" distance, we can change our focus distance like this:

 

Hyper-Focal.jpg

 

In this example, since I'm using f/22, I move the "infinity" mark on the focus ring to the "f/22" mark on the back-side of the depth of field.  Everything between the two f/22 marks on the depth of field scale should be in acceptable focus.  Notice my blue box is much bigger and now everything from about 6' to infinity is in acceptable focus. This change has gained about 6' in the near-foreground area which will now also be in acceptable focus.

 

This concept (the second shot) is the magic "hyperfocal distance" for this 50mm lens at f/22.  There is no other focus distance which can achieve a broader depth of field than this one.

 

DoF marks are still found on many prime lenses, but not so much on zoom lenses... because the DoF depends on the focal length.  Once upon a time, most zoom lenses used a "push/pull" to slide the lens longer or shorter.  Today most lenses have a zoom ring that rotates (no longer a push/pull -- though there are still some push/pull lenses around.)    Push/pull lenses had a sweeping set of arcs to draw the DoF marks -- but it's not possible to do this with zooms that have a rotating ring (which is most modern zooms.)

 

With zoom lenses today, best to look up the depth of field on a table.  If you have a smartphone there are a number of apps you can use.  You can also make printed tables.  

 

To learn about DoF in the beginning, it might require that you consult the tables (or apps) often, but I find that with enough photography you eventually get a feel for how much depth of field you get in a situation.  As you compose favorites types of subjects using favorite lenses and similar compositions and distances, you find the settings that work -- and arrive at the point where you can take a shot, dialing in the correct settings without even really thinking too much about it (because you've done so much shooting.)

 

Tim Campbell
5D III, 5D IV, 60Da

Exactly. I knew you could say it better than me.

However, the COC does depend on the sensor and its MP.  Even how the print or what ever is displayed or viewed.  And, yes, Bob from Boston, all these are related.  You do not have one without the other.  COC usually menas, what the human eye can resolve and what is called the 'blur' factor.  No lens is perrfect at aiming all the light spectrum to a single  point.

EB
EOS 1DX and 1D Mk IV and several lenses!


@ebiggs1 wrote:

Exactly. I knew you could say it better than me.

However, the COC does depend on the sensor and its MP.  Even how the print or what ever is displayed or viewed.  And, yes, Bob from Boston, all these are related.  You do not have one without the other.  COC usually menas, what the human eye can resolve and what is called the 'blur' factor.  No lens is perrfect at aiming all the light spectrum to a single  point.


All true!  Cropping in is not much different than having shot with a longer focal length lens when the shot was taken and it actually effects DoF in the same way.  When you crop and in and enlarge an area, you make everything bigger -- including the blur -- and that reduces the DoF.

 

And "no lens" includes the human eye.  I watched an episode of "Brain Games" (on Netflix).  It's shocking how bad our eyes actually are.... and how much our brain compensates by assembling an image that our eyes don't actually see.

 

Tim Campbell
5D III, 5D IV, 60Da
Announcements
01/18/2023: New firmware version 1.1.1 is available for EOS R6 Mark II
01/09/2023: Help ensure your autofocus is properly aligned with a Canon Precision Alignment
01/03/2023: Welcome to CES 2023!
12/08/2022: New firmware version 1.0.5.1 is available for EOS C70
12/07/2022: New firmware version 1.7.0 is available for EOS R5
12/07/2022: New firmware version 1.7.0 is available for EOS R6
11/22/2022: New firmware available for EOS R3, EOS R7 and EOS R10
11/16/2022: We're thrilled to be ranked among the Best Employers for Veterans in 2022 by Forbes.
08/31/2022: New firmware version 1.1.1 is available for RF 70-200mm L IS USM
08/09/2022: New firmware version 1.2.0 is available for CR-N 300
08/09/2022: New firmware version 1.2.0 is available for CR-N 500
07/14/2022: New firmware version 1.0.1 is available for CR-X300
06/10/2022: Service Notice:UPDATE: Canon Inkjet Printer continuous reboot loop or powering down
06/07/2022: New firmware version 1.3.2 is available for PowerShot G7 X Mark III
05/31/2022: Did someone SAY Badges?
05/26/2022: New firmware version 1.0.5.1 is available for EOS-C500 Mark II
05/26/2022: New firmware version 1.0.3.1 is available for EOS-C300 Mark III
05/10/2022: Keep your Canon gear in optimal condition with a Canon Maintenance Service
05/05/2022: We are excited to announce that we have refreshed the ranking scale within the community!
04/26/2022: New firmware version 1.0.1.1 is available for EOS R5 C
03/23/2022: New firmware version 1.0.3.1 is available for EOS-C70
02/09/2022: Share Your Photos is back!
02/07/2022: New firmware version 1.6.1 is available for EOS-1DX Mark III
01/19/2022: READY FOR ANYTHING EOS-R5 C
01/13/2022: Community Update. We will be retiring the legacy profile avatars on 01/20/2022. Click this link to read more.