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Author Topic: Image clarity  (Read 3448 times)
jnaneshwars
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« on: April 23, 2007, 03:18:51 PM »
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I shot this tulip fields in Skagit county, Washington. The purple tulips in the foreground appear less sharp than the red and white ones and the red ones. I focussed at a point b/w the red and white tulips and the red tulips considering that was the hyperfocal distance. I assumed it to be 1/3 of the frame.
I'd like to know what should have been done.
Any thing good or bad about the image?

Image settings: f-6.7; 1/125s ; 18-55mm lens ; shot on an overcast day.
« Last Edit: April 23, 2007, 03:40:11 PM by jnaneshwars » Logged
jnaneshwars
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« Reply #1 on: April 23, 2007, 03:22:09 PM »
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Sorry I missed the image the first time.
« Last Edit: April 23, 2007, 03:41:23 PM by jnaneshwars » Logged
howiesmith
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« Reply #2 on: April 23, 2007, 04:00:29 PM »
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I shot this tulip fields in Skagit county, Washington. The purple tulips in the foreground appear less sharp than the red and white ones and the red ones. I focussed at a point b/w the red and white tulips and the red tulips considering that was the hyperfocal distance. I assumed it to be 1/3 of the frame.
I'd like to know what should have been done.
Any thing good or bad about the image?

Image settings: f-6.7; 1/125s ; 18-55mm lens ; shot on an overcast day.
[a href=\"index.php?act=findpost&pid=113853\"][{POST_SNAPBACK}][/a]

You don't say what the focal length you used was, just provided a range (18-55mm).  That range would allow the hyperfocal distance to vary by about a factor of 9.

What value of CoC did you use and what was that based on?  You can't determine the hyperfocal distance without it.

If the lens' focal length is small compared to the focus distance (probably true here), the near limit of DoF is about half the hyperfocal or focus distance, not 1/3.
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Ray
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« Reply #3 on: April 23, 2007, 06:58:32 PM »
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Image settings: f-6.7; 1/125s ; 18-55mm lens ; shot on an overcast day.
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You've given us the wrong information. The EXIF data indicates you used a shutter speed of 1/60th. You also used a focal length of 55mm and ISO 100. If you want good DoF (and this is the sort of shot where you do), then f6.7 is simply not a small enough aperture. With the cropped format of the Pentax K10D, you can probably stop down to f13 without too much compromise in absolute resolution.

The K10D has low noise performance up to ISO 400, so you could have increased ISO to maintain the same shutter speed when stopping down.

Assuming you didn't have a tripod,  these are the settings you should have used, in my opinion. 1/60th, f13, ISO 400.

I don't know how many people use Howard's approach in the digital age. It seems a bit cumbersome to me and has the major flaw that, having determined the precise distance one should find an object to focus on, the lens markings on a zoom like your 18-55 will probably not give you that distance, which means you'll probably have to guess, in which case you might as well take 2 or 3 shots focussing on different points in the scene (distance bracketing if you like).
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howiesmith
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« Reply #4 on: April 23, 2007, 07:56:34 PM »
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jnaneshwars, contrary to Ray's comments, this is not my approach.  I borrowed it, copied it, stole it, whatever you prefer but I did not invent it.  It is not mine.

Michael Reichmann for one says there is no difference between film and digital when determining DoF.  I happen to agree with him, but if you don't, take it up with Michael Reichmann, not me.

Contrary to Ray's comments, one does not have to find a subject at the hyperfoacal distance or even the focus distance.  For example, I might want to make an image with an in-focus bush on this side of a canyon, and an in-focus bush on the other side - nothing in between.  Nothing in between to focus on where I might like to focus.

It matters not whether I can measure the focus or hyperfoacal distance or not.  It might be in the middle of the Grand Canyon.  I may have to estimate, or guess where to focus.  But even if I can't measure the focus distance and have to estimate it on my lens, it is far better, in my opinion, to know (even precisely ?) I am trying to focus at precisely 122.3 feet, rather than simply take a flyer - try to focus at a guessed distance that I have no idea what it is, except perhaps it is between this bush and thta one.

You still need a CoC to determine the hyperfocal distance and DoF, whether you can measure them or not.
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Ray
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« Reply #5 on: April 23, 2007, 08:35:28 PM »
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jnaneshwars, contrary to Ray's comments, this is not my approach.  I borrowed it, copied it, stole it, whatever you prefer but I did not invent it.  It is not mine.

Michael Reichmann for one says there is no difference between film and digital when determining DoF.  I happen to agree with him, but if you don't, take it up with Michael Reichmann, not me.

Now, now, Howard. Don't get uptight about this   . I think most people would understand that I am not implying you have invented this system, but rather you have adopted it. I notice again you have this strong tendency to appeal to authority during differences of opinion. Ansel Adams or Michael Reichmann wrote 'such and such'. They are experienced and revered photographers, therefore they must be right.

Surely by now you must know that my view is, all knowledge is provisional.

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It matters not whether I can measure the focus or hyperfoacal distance or not.  It might be in the middle of the Grand Canyon.  I may have to estimate, or guess where to focus.  But even if I can't measure the focus distance and have to estimate it on my lens, it is far better, in my opinion, to know (even precisely ?) I am trying to focus at precisely 122.3 feet, rather than simply take a flyer - try to focus at a guessed distance that I have no idea what it is, except perhaps it is between this bush and thta one.

You have just contradicted yourself in the same paragraph, Howie. If it matters not whether you can measure the hyperfocal distance, there cannot possibly be a reason to guess.

However, I agree, if it is necessary to guess, then you are better off having a precise distance to 'guess around', especially if you lack experience in such matters.

As regards choosing different CoCs in relation to intended print size, I think that's probably another unnecessary complication for most photographers, but a principle one should at least be aware of. I would recommend sticking with a CoC appropriate for the maximum print size in relation to an uninterpolated image at 240ppi.
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Richowens
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« Reply #6 on: April 23, 2007, 09:02:40 PM »
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My approach would be the same as Ray's. Bump the ISO to 400, stop down to at least f11 in aperature priority and set the focus where the purple tulips meet the red&white tulips. Then shoot one at 13 and a third at 16.

Also you need to take in to acount for the wind causing motion blur and try to shoot between gusts. My wife was there a week ago last Friday and said she has never been so cold in her life because of the wind. But she learned well and came back with some decent shots despite shooting with a new camera.

[attachment=2354:attachment]


Rich
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jnaneshwars
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« Reply #7 on: April 23, 2007, 09:19:39 PM »
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My approach would be the same as Ray's. Bump the ISO to 400, stop down to at least f11 in aperature priority and set the focus where the purple tulips meet the red&white tulips. Then shoot one at 13 and a third at 16.

Also you need to take in to acount for the wind causing motion blur and try to shoot between gusts. My wife was there a week ago last Friday and said she has never been so cold in her life because of the wind. But she learned well and came back with some decent shots despite shooting with a new camera.

[attachment=2354:attachment]
Rich
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Thanks for the awesome response guys. Great pic Rich!
I have taken some good snaps but all I was concerned was about the focus area. I note some of the points disucssed above and shall try to implement it. Most images which show a vast expanse of the subject we try to project, usually are in focus and I was trying to do that. I focussed on the bright areas and the dark areas and tried to shoot on an average setting. I shot a couple of more pics but this one turned out to be the better one.
Regarding EXIF data I don't know how it was deduced but I shall double check my exposure settings once again.
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Richowens
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« Reply #8 on: April 23, 2007, 09:40:05 PM »
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Load your photo into Photoshop and go to file info under the file menu. This will pop up a new window with your photo info iin it. Go to advanced and explore.

Rich



[attachment=2355:attachment]
« Last Edit: April 23, 2007, 09:48:04 PM by Richowens » Logged

howiesmith
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« Reply #9 on: April 24, 2007, 12:17:47 PM »
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Time for me to rethink this whole depth of field thing.  I have been apparently overthinking it.

Focus the camera.  Somewhere.  Doesn't seem to matter much so let's say between the near and far things to be in focus.  Half way or 2/3s, whatever.  Or maybe at infinity, according to at least one expert.  Seems to be enough opinions to allow me to focus anywhere I want.

Stop down to f/11.  That should de it.  Shoot.  Then, just to make sure, take a couple extra exposures, say f/13 and f/16.  Now I can't miss.

I don't need to know hyperfocal distance, which is good, because I don't need to know anything about CoC.  This really gets simple.  It can be some cook book value, something related to uninterpating 240 ppi, or maybe something as foolish as what can be seen on the print.  Who looks at the print anyway?  Since no one knows, lucky thing it doesn't matter at all.  Isn't science wonderful?  Just shoot and then print any size I want, to up to uninterpolated 240ppi.

I don't even need to have to have the opinion of any authority on the subject.   What do they know anyway?  How foolish anyway to rely on someone who knows something about the subject.  Question.  If Ray is an authority, is his opinion worthless?  Is not being an authority what qualifies one to know what he he is saying?
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