Ad
Ad
Ad
Pages: « 1 2 [3]   Bottom of Page
Print
Author Topic: 1Ds Mk II major design flaw for landscape photos  (Read 7972 times)
David R. Gurtcheff
Guest
« Reply #40 on: September 29, 2004, 08:16:32 AM »
ReplyReply

[font color=\'#000000\']At small aperatures like f11 or 16, I focus to a point about 1/3 the distance into a landscape, and get sharp focus front to back on my 20"x30" landscape prints (using wide lenses on a 1Ds). Simple, but it works for me.
Dave[/font]
Logged
Tim Gray
Sr. Member
****
Offline Offline

Posts: 2002



WWW
« Reply #41 on: September 29, 2004, 12:15:33 PM »
ReplyReply

[font color=\'#000000\']1. The 1/3 is a recognition that when you focus on any given point the depth of field you get will go roughly from 1/3 in front to 2/3 behind the point of focus (ie 1/3 of the depth of field) - for finite DOFs (ie not dof to infinity). The DOF is not equally in front or behind the POF. This also might be a reference to the hyperfocal distance which is defined as the distance at which 1/2 of that distance to infinity is in focus.

2. That's the way it works. Any given DOF calculation makes assumptions about the viewing distance and the size of the print - this drives the COC number. DOF isn't binary - the larger you print and the closer you view the less-in-focus the image is going to appear regardless of the calculated DOF.

The dimness/sharpness is totally unlrelated to the dark room scenario you mention. The DOF preview simply stops the lens down to the selected aperture. At f22 the hole is pretty dang small so appears very dim, but the higher the f stop the greater the dof.

3. No, as noted above the DOF preview simply stops down the f stop.

4. You can certainly rely on the "relativeness" of the DOF, ie the longer the FL, closer the subject and wider the aperture, the more the foreground and background will be blurred. As I said earlier, what you see in a print adds the size of the print and the viewing distance to the mix.

Maybe part of the confusion comes in that what is in focus (technically) is the 2 diminsional plane at the point of focus.  The farther you diverge from that plane the more you will tend to see blur.  It's not true that everyting within a DOF is in fact "sharp" or "in focus", only that based on the assumptions reflected in the chosen COC it will "appear" sharp.[/font]
Logged
boku
Sr. Member
****
Offline Offline

Posts: 1493



WWW
« Reply #42 on: September 29, 2004, 07:32:37 PM »
ReplyReply

[font color=\'#000000\']IMHO, the underlying formula uses "limits" as we approach infinity. Here's an empirical proposal that will get you there. For grand landscapes, assume your distant point is 5000 ft. As far as the lens is concerned, lim(f->infinity) ~ 5000 ft is certainly close enough. Now you have a useful far point you can crank into your DOF formula.[/font]
Logged

Bob Kulon

Oh, one more thing...
Play it Straight and Play it True, my Brother.
Tim Gray
Sr. Member
****
Offline Offline

Posts: 2002



WWW
« Reply #43 on: September 30, 2004, 08:13:46 AM »
ReplyReply

[font color=\'#000000\']
Quote
Jonathan and Tim appear to be discussing two different aspects of COC and hyperfocusing. I'd greatly appreciate clarification of the relationship between these two, and thank Tim and Jonathan in advance for their response:

Jonathan argues that the 1Ds demands a more restrictive COC than does film:

I don't think our positions are incompatible. What Jonathan is getting at (if I may take the liberty) is that you might as well maximize sharpness since the ultimate purposes for which most folks would use the 1Ds are not 8x10 (you don't need a 1Ds for 8x10s) but larger. If you're shooting for large framed, displayed prints the more conservative a COC you use the better.

But in the end there's no free lunch - the sweet spot is f8 - f11 +/- for most lenses, and as you move towards f32 other un-desirable stuff starts to happen. Ultimate DOF is going to be driven by lots of comprimises to the photographers intent. Is there motion? - problematical for long exposures. What's the composition, WA lends itself naturally to deep DOF, but not telephotos or macros.

The issue is important if you are using a calculator, since it will very likely use .03 or thereabouts for full frame and amend that for the smaller sensors (if it's a "good" calculator). If you need to factor in size of print etc. the "standard" coc is going to be misleading and you might as well use Jonathan's suggestion.

My only caveat is that even being conservative in using a smaller COC, I'm still not convinced that a 1 pixel COC is appropriate. I don't have the math, I'm simply recalling other discussions.... The question is under what size/viewing conditions is a 4 square block (next logical size up from 1 pixel) perceived, not as a point, but as a disk - that's a testable question.[/font]
Logged
Jack Flesher
Sr. Member
****
Offline Offline

Posts: 2595



WWW
« Reply #44 on: September 30, 2004, 03:13:56 PM »
ReplyReply

[font color=\'#000000\']FOR THE RECORD:

In optics, the practical "infinity" is defined as 100x the focal length of the lens.  I cannot find the reference, but I believe this standard was established for f2 and smaller apertures. Thus, set the lens on infinity and everything from 100x focal to infinity will fall within CoC limits.[/font]
Logged

Jack Flesher
Sr. Member
****
Offline Offline

Posts: 2595



WWW
« Reply #45 on: September 30, 2004, 11:06:27 PM »
ReplyReply

[font color=\'#000000\']Howard:

Your position and crops do not change the effective DOF -- it simply changes the CoC YOU are now willing to accept...    

And infinity is still 100x the lens' focal length.[/font]
Logged

Dan Heller
Newbie
*
Offline Offline

Posts: 2


WWW
« Reply #46 on: January 06, 2005, 10:24:59 PM »
ReplyReply

Much as I agree with Marty's statement about the obvious ease of use that DEP mode gave us (and it applies to far more photogs than just landscape shooters, BTW), discussing the various merits of the fuction at this juncture is like warning the captain of the Titanic that there are ice bergs ahead, all while the ship is sinking.

In other words, it's too late for that. Let's move on.

To me, the answer is simple: custom functions. There's already one for turning ON and OFF all the other shooting modes, like "P", "TV", "Bulb", etc... Why not just have DEP mode "off" by default so as to make the next version of the camera look exactly like this version? Those who don't use it don't have to be bothered with it... whereas, those of us who need and depend on it, will be made whole again.  Doesn't this seem like a perfectly reasonable win-win resolution?

If Canon claims that focus groups said that they don't use DEP mode, what did those same people say about the mode where the shutter doesn't release until something moves into the focus plane at an AF point? Sure, I can see the one time in a million that I could use it, but can you really say that MORE people want that over DEP mode? No one's complaining that it's in the CF list--in fact, no one's complaining that the CF list is even too big.

There simply must be a rational, reasonable discussion on the matter moving forward.

One thing that I must also agree with Marty about: this isn't going to happen unless photogs with clout--and who have the ear of decision-makers at Canon--say something. If it's product reviewers, fine by me.
Logged

Ralph Eisenberg
Jr. Member
**
Offline Offline

Posts: 82


« Reply #47 on: January 09, 2005, 03:54:06 PM »
ReplyReply

Many thanks for this excellent thread. I certainly miss DEP on the 1Ds2 and with others regret that it could not simply be disabled as a personal function, should one so desire.
Logged

Ralph
Pages: « 1 2 [3]   Top of Page
Print
Jump to:  

Ad
Ad
Ad