| Author | Thread |
|
|
11/18/2010 10:10:59 AM · #1 |
I feel dimmer than usual asking this question but it is truly bothering me. Please tell me if I've got this all screwed up. Though familiar with the principle I've really only started to pay close attention due to getting close to the ground lately with my 12-24mm.
Why does hyperfocal focusing differ from subject focusing? And why hasn't a system been created to emphasize this difference?
Example:
I'm shooting a creek at 12mm, f11, with the goal of having a clear rock two feet away for foreground and sharp as far as the eye can see.
Scenario 1: If I focus on said rock in the creek two feet in front of me it will be in focus but sharpness will drop off after about 10 feet or so. If I focus on a rock 10 feet away the focus will continue to infinity but the rock in the foreground will now be out OOF.
Scenario 2: Still at f11, if I switch to manual focus and move the infinity sign over f11 in the meter I then will have sharpness from about 1.5 feet through infinity.
Obviously scenario 2 is ideal for this situation. But I do not understand why.
If it is the same aperture how can the depth of field change? Is it because I've essentially eliminated the subject from consideration and therefore any specific focal point? By focusing at nothing I gain everything? Is this some deep experience?
Secondly, why has no one created a focusing system that incorporates this? I guess the easy answer is it's cheaper to just switch to manual focusing mode. But if you could simply indicate the desired hyperfocal distance to your subject you could make better use of your settings for exposure and noise if the camera could give you feedback. Kind of how Tv mode will select Av for you, hyperfocal mode could also select Av for you given your indicated hyperfocal point and assuming focus range to infinity.
Does any of this make sense? Have I lost my mind? All illumination greatly appreciated.
|
|
|
|
11/18/2010 10:27:41 AM · #2 |
Because when you focus 10 feet away your depth of field is PAST infinity, so you are effectively "wasting" some of your focus. By changing your focus so the f11 mark is over the inifinity mark you are gaining some "free" extra foreground focus.
I have a couple of images I'll try and find .... |
|
|
|
11/18/2010 10:31:00 AM · #3 |
Thanks. That makes sense, certainly, but if I focus two feet away I've only got focus through about 10 feet or so. But if I don't focus and align the infinity and f/11 mark I will have sharp focus from my subject through infinity. That's the part I'm really hung up on.
Edit: I'd also post examples of this but won't be home for hours and don't have them on me here at work.
Thanks again for the help.
Message edited by author 2010-11-18 10:33:04. |
|
|
|
11/18/2010 10:33:38 AM · #4 |
You can use the Depth of field scale to increase the dof. The aperture is shown on the lower scale and shows the dof for a given aperture, in this case focused at 1 meter, if your aperture was f/8 your photograph would be focused from about 0.82m to 1.3m If you set the aperture to f/16 you would be focused from about 0.7m to 2m.
Focusing at 4 meters with this focal length lens would mean that you could use f/8 and everything woiuld be focused from 2.1m to infinity. If you used f/16 and everything woiuld be focused from 1.4m to infinity. However, you are "wasting" foreground focus as you cannot focus past infinity!
If you reset the focus of the lens using the scale to line up f/16 with infinity you will now have everything from 1.1m to infinity in focus, you have got that extra dof for free!
If you know what focal length and aperture you are going to use you can focus the lens before leaving the house!
To calculate for a specifc lens see //www.dofmaster.com/doftable.html |
|
|
|
11/18/2010 10:35:06 AM · #5 |
Originally posted by bohemka:
Thanks. That makes sense, certainly, but if I focus two feet away I've only got focus through about 10 feet or so. But if I don't focus and align the infinity and f/11 mark I will have sharp focus from my subject through infinity. That's the part I'm really hung up on.
|
Why do you think you only have focus through 10 feet?
eta. I *think* I understand what you are asking.
In this image you focus 2.1m away and at f16 everything from 1.1m away will be in focus ... I think you are saying, if you were using this example at f16, you are focusing at 1.1m when you need to focus at 2.1m
Message edited by author 2010-11-18 10:48:31. |
|
|
|
11/18/2010 12:26:09 PM · #6 |
Originally posted by bohemka:
By focusing at nothing I gain everything? Is this some deep experience? |
Yes. |
|
|
|
11/18/2010 12:28:00 PM · #7 |
I second the recommendation of DoFMaster as both a learning tool (the online version) and a tool for use in the field (printed tables or the physical calculator). But, see caution below.
What you are doing when you align the far f/11 mark over the infinity mark is equivalent to setting the hyperfocal distance. Both attempt to set the far limit of focus to infinity.
Now, one word of caution in all this. The math behind determination of the hyperfocal distance depends on a variable called the CoC (Circle of Confusion). Standard values for this variable, including those used in DoFMaster by default, will result in an overstatement of the DoF, so if you follow the recommendations to the letter, you will probably notice that objects at infinity are slightly soft. If you wish to avoid this when using DoFMaster, set the CoC manually to *twice* the pixel pitch of your sensor. The manual selections are at the bottom of the drop-down, below the list of cameras. |
|
|
|
11/18/2010 12:28:45 PM · #8 |
Originally posted by tanguera:
Originally posted by bohemka:
By focusing at nothing I gain everything? Is this some deep experience? |
Yes. |
+1
This is the zen of hyperfocal photography :-) |
|
|
|
11/18/2010 12:33:38 PM · #9 |
Originally posted by bohemka:
Secondly, why has no one created a focusing system that incorporates this? |
Canon 50D, ADEP... :) |
|
|
|
11/18/2010 07:31:12 PM · #10 |
Originally posted by kirbic:
If you wish to avoid this when using DoFMaster, set the CoC manually to *twice* the pixel pitch of your sensor. |
I've seen you say these words before and I follow them. My CoC entered is half what it should be for calculations. Thanks a lot for the help. |
|
|
|
11/19/2010 04:45:17 AM · #11 |
Originally posted by bobonacus:
If you know what focal length and aperture you are going to use you can focus the lens before leaving the house! |
Funnily enough I have been doing just that with that lens. f11 at 12mm, Av mode, auto iso with minimum shutter speed at 1/80s. It's a really expensive point and shoot. |
|
|
|
11/19/2010 11:51:13 AM · #12 |
Originally posted by bohemka:
Originally posted by bobonacus:
If you know what focal length and aperture you are going to use you can focus the lens before leaving the house! |
Funnily enough I have been doing just that with that lens. f11 at 12mm, Av mode, auto iso with minimum shutter speed at 1/80s. It's a really expensive point and shoot. |
It's ironic, that what this thread is discussing is "how to manual-focus for extreme DOF", and that one of the things we PAY for when we shell out the big bucks is a camera that allows us NOT to use automatic functions, like focus in this case. The problem with P&S cameras, or one of them anyway, is that they mostly won't manual focus at all, or if they DO have MF option it's often really awkward/cumbersome to use. Gawd bless our DSLRs with their perfectly retro "twist the lens barrel" focusing :-)
R. |
|
|
|
11/19/2010 12:00:42 PM · #13 |
This could of course only be me. BUT I've more often than not used my 1D and 5D's as P&S cameras. Left them on "P" and let the autofocus do the job. As already has been discussed here, you won't get the optimal focus setting and DOF when you do this (if you're after a deep DOF especially). And many times I discover when it's too late that the camera focused on a nose or arm instead of the eyes.
After I started using the Leica (no autofocus), I've been forced to think about focus all the time and as a result I get better DOF/depth in my images. This is not the case for everyone of course, but was like for me since I don't take full advantage of my DSLR's. The manual focus on DSLR's are unfortunately difficult to use for me since my eyes are deteriorating and I never feel I can trust what I see. |
|
|
|
11/19/2010 12:28:01 PM · #14 |
An essential in-th-field tool for the landscape photographer. I use it all the time.
//www.dofmaster.com/iphone.html |
|
|
|
11/19/2010 12:34:32 PM · #15 |
Originally posted by TrollMan:
After I started using the Leica (no autofocus), I've been forced to think about focus all the time and as a result I get better DOF/depth in my images. This is not the case for everyone of course, but was like for me since I don't take full advantage of my DSLR's. The manual focus on DSLR's are unfortunately difficult to use for me since my eyes are deteriorating and I never feel I can trust what I see. |
I hear you. When you rely on manual focus, you really start to think about strategies for focusing, and the result is better images, at least when we have *time* to strategize, LOL.
I also agree that most modern DSLRs & lenses are not the best for manual focus, although the situation is better than it used to be. At least on the higher end models, we have more choice in finder screens to optimize for manual focusing. But distance scales, when they are present at all, are not what they used to be, and focus rings have very short travel (with the exception of true macro lenses), making critical focus difficult. |
|
|
|
11/19/2010 12:37:25 PM · #16 |
Originally posted by Bear_Music:
Originally posted by bohemka:
Originally posted by bobonacus:
If you know what focal length and aperture you are going to use you can focus the lens before leaving the house! |
Funnily enough I have been doing just that with that lens. f11 at 12mm, Av mode, auto iso with minimum shutter speed at 1/80s. It's a really expensive point and shoot. |
It's ironic, that what this thread is discussing is "how to manual-focus for extreme DOF", and that one of the things we PAY for when we shell out the big bucks is a camera that allows us NOT to use automatic functions, like focus in this case. The problem with P&S cameras, or one of them anyway, is that they mostly won't manual focus at all, or if they DO have MF option it's often really awkward/cumbersome to use. Gawd bless our DSLRs with their perfectly retro "twist the lens barrel" focusing :-)
R. |
LOL Robert....
Funny thing is that, due to smaller sensor size, P&S cameras are MUCH better at doing extreme DOF stuff, as they're able to focus from 1" to infinity... (see winning "table shot" entry done with an iPhone)... |
|
|
|
11/19/2010 01:03:19 PM · #17 |
Originally posted by coryboehne:
Funny thing is that, due to smaller sensor size, P&S cameras are MUCH better at doing extreme DOF stuff, as they're able to focus from 1" to infinity... (see winning "table shot" entry done with an iPhone)... |
Oh, you betcha. I remember thinking, with my Fuji Finepix 4900Z, that I was an absolute whiz at macro, too. In my hubris I passed it off to my quarter-century of professional experience (never mind that I almost never shot macros in those years). Then I bought the 20D and the 60mm macro lens. Boy, that was a humbling experience...
Even talking wide-angle, close-field landscape work, the difference between APS-C and FF (20D/7D v 5D, 10mm vs 17mm), the difference is night and day. I have to work MUCH Harder at 17mm getting pics that required little or no thought at 10mm. Meanwhile this little Sony P&S I inherited from Penny has essentially infinite DOF at its widest setting. Heck, the dang thing only stops down to f/8, LOL.
R. |
|
|
|
11/19/2010 01:26:23 PM · #18 |
Originally posted by coryboehne:
Funny thing is that, due to smaller sensor size, P&S cameras are MUCH better at doing extreme DOF stuff, as they're able to focus from 1" to infinity... (see winning "table shot" entry done with an iPhone)... |
I'm sure the small sensor size helps- It also helps that the sensor is much closer to the lens. My Leica sensor is full format (same size as the 5dm2 sensor) but still have a great depth of field. I took this picture today in a real estate shoot.
The aperture was set to F 2.0 due to it being dusk/overcast and not very bright. The image is still sharp to infinity. I did use the hyperfocal distance when I focused and ignored focusing on the house I photographed. I did not use this picture of course but it does show the DOF.
ETA. The only negative thing with using this lens totally wide open is that is vignettes slightly as can be seen. Any other aperture there is no visible vignetting.
Message edited by author 2010-11-19 13:31:35. |
|
|
|
11/19/2010 01:51:04 PM · #19 |
| Certainly clear as far as you can see, and, importantly, up close as well. If that tree had been out of focus the shot would have been ruined. If you had focused on that tree the depth of field shrinks to nothing at f2. |
|
|
|
11/19/2010 01:54:14 PM · #20 |
Originally posted by TrollMan:
I'm sure the small sensor size helps- It also helps that the sensor is much closer to the lens. My Leica sensor is full format (same size as the 5dm2 sensor) but still have a great depth of field. I took this picture today in a real estate shoot. |
How close the sensor is to the lens is not relevant, I don't think. It's all about the physical size of the aperture. WA lenses, at a given f-number, have more DOF than teles at the same f-number BECAUSE the number represents a smaller and smaller physical aperture the shorter the focal length becomes.
Your 35mm lens, at f/2, has an aperture of 17.5mm. That's roughly equivalent to f/5.6 on a 100mm lens. Therefore the 100mm at 5.6, standing at the same spot and focused on the same point, would show identical DOF to what we're seeing from the 35mm in this shot. In theory, if you cropped the 35mm to the same FOV as the 100mm shows, you'd be able to overlay those images and see no difference at all toggling between them. Except for any increased noise due to the crop, of course.
In the particular image, I don't see anything remarkable about the DOF. On FF camera 35mm is a moderate wide angle, and considerable DOF is expected. Nevertheless, the foreground of the shot is distinctly not in focus; the balcony and gas tank in the lower left, the fence extension bottom center, the red/blue sign lower right, these are not sharp. One can see the sharpness increasing as one travels into the image. Granted, some of this may be due to decreased edge/corner resolution on the Summicron when wide/open (to be expected) but, curiously, part of the reason why THAT is happening IS because the lens on the Leica is closer to the sensor plane, and there's an extreme difference in how far the light has to travel to reach the edges of the large sensor, versus its center.
But you know all that, right? My point is, I just don't think (and I could be wrong, but I've never heard of it), that DOF increases as lens are mounted closer and closer to the sensor plane.
R. |
|
|
|
11/19/2010 01:55:24 PM · #21 |
Originally posted by bohemka:
Certainly clear as far as you can see, and, importantly, up close as well. If that tree had been out of focus the shot would have been ruined. If you had focused on that tree the depth of field shrinks to nothing at f2. |
"That tree" IS out of focus; not badly so, but it's nowhere near as sharp as the middle-ground house is.
R. |
|
|
|
11/19/2010 01:56:05 PM · #22 |
Originally posted by coryboehne:
Funny thing is that, due to smaller sensor size, P&S cameras are MUCH better at doing extreme DOF stuff, as they're able to focus from 1" to infinity... (see winning "table shot" entry done with an iPhone)... |
It's possible to get a shallow DOF with a P&S camera on auto ... one of my early (2003) entries 
My Canon has manual focus, but it's a super-PITA procedure involving two buttons at the same time ... :-(
On the other hand, with the EVF, I see a preview of the actual exposure with half-pressing the shutter, so it's pretty easy to make adjustments before shooting. |
|
|
|
11/19/2010 02:05:59 PM · #23 |
You could very well be right about the proximity to the sensor Robert. I go a little bit about what I read, but this only in review form (which tends to be a little over the edge) and not the real theory.
I realize of course that the foreground is not in focus but that was not the purpose with this shot since everything on the sides usually get cropped out. The picture was obviously of the grey house on the left. |
|
|
|
11/19/2010 02:14:16 PM · #24 |
Originally posted by TrollMan:
I realize of course that the foreground is not in focus but that was not the purpose with this shot since everything on the sides usually get cropped out. The picture was obviously of the grey house on the left. |
Sure, I realize that. This was just a discussion of the DOF properties of the given lens/aperture combination, and my point is/was, I don't get the sense, from this image at least, of anything out-of-the-ordinary, DOF wise. Nice houses though, nice views :-)
R. |
|
|
|
11/19/2010 02:18:20 PM · #25 |
Originally posted by Bear_Music:
Originally posted by TrollMan:
I realize of course that the foreground is not in focus but that was not the purpose with this shot since everything on the sides usually get cropped out. The picture was obviously of the grey house on the left. |
Sure, I realize that. This was just a discussion of the DOF properties of the given lens/aperture combination, and my point is/was, I don't get the sense, from this image at least, of anything out-of-the-ordinary, DOF wise. Nice houses though, nice views :-)
R. |
Thanks for info though Robert. And I found this great article on the subject which supports your theory.
Houses in Norway are very seldom built in a row and are kind of scattered around on the hills like you see here. Makes it interesting and fun being a real estate photographer :) Today I got permission from a neighbor to use their balcony for taking pictures of the back of the house. |
|
