topic Re: DSLR 101 3.0 in EOS DSLR & Mirrorless Cameras

DSLR 101 3.0

jazzman1 — Fri, 10 Jul 2015 01:44:08 GMT

Re: DSLR 101 3.0

RobertTheFat — Sat, 06 Jun 2015 15:19:04 GMT

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.

Re: DSLR 101 3.0

jazzman1 — Sat, 06 Jun 2015 18:12:05 GMT

@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

jazzman1 — Sat, 06 Jun 2015 18:43:26 GMT

Re: DSLR 101 3.0

19m ago

@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.

Re: DSLR 101 3.0

jrhoffman75 — Sat, 06 Jun 2015 21:40:56 GMT

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.

Re: DSLR 101 3.0

jazzman1 — Sat, 06 Jun 2015 23:59:24 GMT

@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.

Re: DSLR 101 3.0

ebiggs1 — Sun, 07 Jun 2015 13:39:19 GMT

"... 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.

Re: DSLR 101 3.0

jrhoffman75 — Sun, 07 Jun 2015 14:24:11 GMT

Negative. That's not what I want talking about. I was talking about when you focus at a particular point that distance is perfectly sharp and a range around that is acceptable based on the circle of confusion that establishes DOF. One might control DOF by choosing aperture to selectively highlight the subject.

Hyperfocal distance you select a focus point so that the closet and furthest item of interest is in acceptable focus relying on DOF.

I know you know this; I just to be sure all readers do.

Re: DSLR 101 3.0

ebiggs1 — Sun, 07 Jun 2015 14:42:17 GMT

Not negative. They are really extremely related to each other. Most people wil be happier with hyperfocal distance than COC. COC depends on the sensor size and viewing medium. Hyperfocal distance is lens driven.

Re: DSLR 101 3.0

RobertTheFat — Sun, 07 Jun 2015 16:17:10 GMT

@ebiggs1 wrote:
Not negative. They are really extremely related to each other. Most people wil be happier with hyperfocal distance than COC. COC depends on the sensor size and viewing medium. Hyperfocal distance is lens driven.

a. Isn't the whole concept of hyperfocal distance based on the CoC (i.e., the appearance of being in focus because other factors keep you from telling the difference)?

b. Hyperfocal distance is useful only if the in-focus range has to extend to infinity. Or am I missing something?

Re: DSLR 101 3.0

TCampbell — Sun, 07 Jun 2015 16:48:22 GMT

@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:

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:

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.)

Re: DSLR 101 3.0

ebiggs1 — Sun, 07 Jun 2015 16:56:35 GMT

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.

Re: DSLR 101 3.0

TCampbell — Sun, 07 Jun 2015 17:28:24 GMT

@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.

Re: DSLR 101 3.0

jazzman1 — Sun, 07 Jun 2015 17:43:18 GMT

This is a article, I think, is refuting DOF as I understand you guys are explaining it. I'm not saying it is, I don't know...I'm learning. Is he, "Ken", saying the same thing you guys are, or is his take a different spin on DOF??? Your feedback of what Ken says here would be very helpful..

http://www.kenrockwell.com/tech/focus.htm

Re: DSLR 101 3.0

ebiggs1 — Sun, 07 Jun 2015 19:30:11 GMT

Rockwell is OK but he is loose with details and accuracy soemtimes.

Re: DSLR 101 3.0

jazzman1 — Sun, 07 Jun 2015 20:04:40 GMT

Thanks Obiwan, that's good info for me. I did'nt know much about him and was reluctant to accept with he said on face value. I do know ehough to not run with just anything I read online.

Re: DSLR 101 3.0

TCampbell — Sun, 07 Jun 2015 21:26:36 GMT

@jazzman1 wrote:

This is a article, I think, is refuting DOF as I understand you guys are explaining it. I'm not saying it is, I don't know...I'm learning. Is he, "Ken", saying the same thing you guys are, or is his take a different spin on DOF??? Your feedback of what Ken says here would be very helpful..

http://www.kenrockwell.com/tech/focus.htm

Well... I made it all the way to the 2nd paragraph... and Ken is already wrong. <sigh>

Ken is a bit of a hack. He blogs to suppliment income and sometimes he says controversial or just out-right wrong stuff. I suspect part of the time he does it because he doesn't know... and part of the time he does it because controversy drives traffic to his website.

My feedback on Ken is.... don't read Ken.

Re: DSLR 101 3.0

jazzman1 — Mon, 08 Jun 2015 00:57:46 GMT

@TCampbell wrote:
@jazzman1 wrote:

This is a article, I think, is refuting DOF as I understand you guys are explaining it. I'm not saying it is, I don't know...I'm learning. Is he, "Ken", saying the same thing you guys are, or is his take a different spin on DOF??? Your feedback of what Ken says here would be very helpful..

http://www.kenrockwell.com/tech/focus.htm
Well... I made it all the way to the 2nd paragraph... and Ken is already wrong. <sigh>

Ken is a bit of a hack. He blogs to suppliment income and sometimes he says controversial or just out-right wrong stuff. I suspect part of the time he does it because he doesn't know... and part of the time he does it because controversy drives traffic to his website.

My feedback on Ken is.... don't read Ken.

LOL LOL LOL...coming from you and Biggs says alot. I know all I need to know about his opinion.....Thanks much.

BTW...Since this topic is DSLR 103 3.0, Everything you guys say here may be valuable, to not just me, but also other newbies who may look in. Some of you peeps are amazing with the knowledge you have. Won't mention any names, to protect the innocent, but a few of you guys are Human Photography Dictionaries.

Re: DSLR 101 3.0

jazzman1 — Mon, 08 Jun 2015 16:17:51 GMT

Anyone know anything about a Photographer named "David Peterson". I've been geting literature about photography courses he teaches online. Any info would help.

Re: DSLR 101 3.0

jazzman1 — Wed, 10 Jun 2015 08:56:05 GMT

I'm not sure which way the Canon 70-300mmL lens "Ring Mount" attaches to the lens the correct way. I tried both ways with the foot pointing backward toward the camera, and the opposite way, pointing out away from the camera. Weight distrubution seemed best with the ring foot pointing forward away from the camera, but I want to make sure that's best way. Which way is right, or is there a right and wrong way? Their was no instructions in the box, and this is my 1st heavy L lens.