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Old Nov 5, 2006, 8:38 PM   #11
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Thanks for the informative replys.

I just did a few more tests and got better results this time.

100% crops no PP:



I guess the hill in the distance is kinda in focus, just soft @ 1.7

Again, 100% crops:



Again the tree line in the far distance is focused but soft.

Not sure if that is normal, definitely better than the last set of pics but disappointing that any 1.7 shot I take is no good.



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Old Nov 5, 2006, 10:33 PM   #12
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I came across this website. It has some great explanations on blur and depth of field, etc., which I believe that your question essentially comes down to. Also, there are several calculators that you can use, that will probably help (much better than my slide rules in optics), along with some images explaining the points that are being made.

http://www.bobatkins.com/photography...ound_blur.html
http://www.bobatkins.com/photography...ield_calc.html
http://www.bobatkins.com/photography...l/dofcalc.html
http://www.bobatkins.com/photography...igitaldof.html
http://www.bobatkins.com/photography...cal/bokeh.html

Essentially there are only a few reasons you would want to use the lens wide open at f1.7

1. low light situations
2. settings where you wish just the contents of a small thin plane in front of the camera to be in focus with the rest (foreground and background) out of focus.
3. ?????

Came across another great site. Depth of Field vs Lens Sharpness - two different things....

http://www.normankoren.com/Tutorials/MTF6.html
http://www.cinematography.net/Pages%...0sharpness.htm
http://www.luminous-landscape.com/tutorials/sharp.shtml
http://www.luminous-landscape.com/tu...harpness.shtml
http://www.tut.fi/units/arc/amltech/propic/DoF.htm

Here is the mathematical answer to your question...

http://www.kenrockwell.com/tech/resolution-myth.htm
"At f/1.4 the depth of field is so paper-thin that the region of sharpness rarely was where I wanted it."

Here is another web page with a great demonstration of f stop vs sharpness

http://www.kenrockwell.com/nikon/50-...on/f-stops.htm

Here is a set of tests similiar to yours, however look at how the picture lays out compared to your neighborhood (no complaints, just a better situation for the test).

f1.4 to f4 -
http://www.kenrockwell.com/nikon/50-.../sharpness.htm
f5.6 to f 32
http://www.kenrockwell.com/nikon/50-...arpness-56.htm

... hope that helps.

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Old Nov 6, 2006, 3:36 AM   #13
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Thanks for that great reply!
I'm reading through all the links now.
The Ken Rockwell ones are especially useful and makes me look totally stupid since it shows me there's nothing wrong with my lense at all

Thanks for all the help guys and gals and sorry for wasting everyones time with a stupid question!

Here's a series of shots I took yesterday for a Weekly Photography Challenge on another forum.
The theme was Triptych


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Old Nov 6, 2006, 4:07 AM   #14
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not only is there nothing wrong with it, looks like it's a great lens!


Very nice photos nadnerb
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Old Nov 6, 2006, 8:29 AM   #15
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Your flowers are wonderful!!!! Excellent - much better than anything, I have done! By the way - there is no such thing as a stupid question!

If you again look at these three examples, the first 2 are wonderful examples of depth of field, and use of f stops.
The first one - the pink flower, the foreground is in focus, with the pettle off to the left and underneath, slightly out of focus (notice the water drops). The difference in depth between the two pettles can not be that much - 1/4 of an inch? So this is again an excellent example depth of field. Also, the image is razor sharp - same lens?

The second one - yellow flower - same thing - the flower bud in the middle is very sharp and in focus with the outer pettles very crisp - due to the f stop used and the width of the depth of field. - I am betting that it is a larger f stop that the first pink one?
My composition is not as good as yours (I do not like tripods) - my interest is in landscapes and architecture, but the math and how it is applied, why things are - based on it, is not a problem.
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