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12-05-2010, 05:04 PM   #916
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Frogfish: From the World Expo in Shanghai.

Mr Froggy--these are splendid!

12-06-2010, 05:23 AM   #917
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QuoteOriginally posted by Jewelltrail Quote
Mr Froggy--these are splendid!
Thank you kind Sir ! More to come when I've PP'd them.
12-06-2010, 01:35 PM   #918
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[langtitle=sk]Sigma 10 - 20 in Central Europe[/langtitle]

From Holiday in Soud Bohemia
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Last edited by Franki55; 12-28-2010 at 10:13 AM.
12-06-2010, 08:38 PM   #919
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the last one is awesome sharp.. what aperture did you use?

12-07-2010, 03:05 AM   #920
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12-07-2010, 11:19 AM   #921
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Rustynail: the last one is awesome sharp.. what aperture did you use?
I'm not sure of the aperture he used in that shot, but can say, when focus is on, this lens has excellent sharpness. It is prone, however, to focus errors because of its wide view and minute movement to achieve focus.

Just look at the variation in sharpness in "Franki55's" shots right above us--particularly note the night/water scene--very soft--I see this all the time here in the thread--especially in low light scenes like these. This is why so many of us who shoot this lens use the hyperfocal point to get accurate focus.

Last edited by Jewelltrail; 12-07-2010 at 11:22 PM.
12-07-2010, 12:32 PM   #922
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QuoteOriginally posted by Jewelltrail Quote
This is why so many of us who shoot this lens use the hyperfocal point to get accurate focus
What do you mean by the hyperfocal length?

12-07-2010, 11:19 PM   #923
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Hyperfocal Point

More accurately known as the “Hyper Focal” distance, it simply means the distance setting at any aperture, which produces the maximum depth of field. In other words, it is the focus distance which will provide the most area of sharpness for a given aperture and focal length. The example typically used here for this thread is for f8 & 10mm, since they are popular settings to get great shots. Now use this formula, plugging in the values when needed:



Where H= the Hyperfocal distance in mm, f is the lens focal length in mm, N= the f-number, c= circle of confusion in mm. The circle of confusion is a mathematical construct-- Just use .020mm for small format Pentax sensors in this equation--do some research if you want to know why this number is used.

So, for example, I want H for my Sigma 10-20mm. I am shooting @ f8, 10mm. F squared=100 (Nc)=.16 100 divided by .16=625mm Now add f to 625=635. To get the answer in meters, divide by 1000, to get the answers in feet divide 635 by 304.8. So, for example, 635 divided by 1000= .635 meters. It is better to go just beyond the Hyperfocal distance, so take out your Sigma lens, whenever you want to shoot f8 @ 10mm, and move the focus ring until it aligns near 1 meter.

Last edited by Jewelltrail; 12-08-2010 at 12:14 AM.
12-08-2010, 10:16 AM   #924
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[langtitle=sk]Sigma 10-20 and Apollo Bridge[/langtitle]

Sorry my English is not very good

Apollo Bridge on The Danube in Bratislava , Slovak Republic
is very most photography Architecture in City , is very Photogenic


My version " Negative colors "

Last edited by Franki55; 12-28-2010 at 10:13 AM.
12-09-2010, 03:12 AM   #925
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QuoteOriginally posted by Jewelltrail Quote
It is better to go just beyond the Hyperfocal distance, so take out your Sigma lens, whenever you want to shoot f8 @ 10mm, and move the focus ring until it aligns near 1 meter.
you mean you have to use the manual focus? What about when using AF?
12-09-2010, 11:09 AM   #926
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I believe you essentially treat the lens like a prime once you get the wideness you want through the focal length. Then you must simply walk to where the subject is in focus, otherwise you would ruin the hyperfocal distance. This is just a guess of course, as I am pretty confused about the whole thing anyways.
12-09-2010, 05:31 PM   #927
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QuoteOriginally posted by rustynail925 Quote
you mean you have to use the manual focus? What about when using AF?
rustynail, at 10mm, the 10-20mm lens doesn't Autofocus well, especially indoors or in low light. Its even hard to manually focus as well since most of the screen looks in focus. So many of us, i believe will just set the focus manually according to the distance marks and call it good enough. Focus is not that important of an item in Ultra wide angle lens photography - read that off the internet so must be true :-)

at 12mm and above, the lens AF tends to start working well again. just one of those idiosyncracies about the 10-20 lens. I know this sounds like a worse problem than it is, just start using it and it just is not a problem

best wishes,
12-09-2010, 09:19 PM   #928
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Rustynail925: you mean you have to use the manual focus? What about when using AF?
Phil hit the nails on the head. However, if you are happy with your AF @ ultra-wide, then stay with it. Using the hyperfocal distance is simple, and guarantees success. I have made hikes up to 23 miles in one day, and grasp fully I may never be in places like that ever again. For me, the certainty the hyperfocal distance offers is too assuring to pass up. Using the correct hyperfocal distance assures you the Max DOF for the shot. This does not mean AF will not do the job, but it is notorious, on the Sigma @ widest settings, for failing. And even if it gets an acceptably sharp shot, this doesn't mean it could not be better. Who came to DSLRs for merely "acceptably sharp" photos? Not me--I want the most out of my equipment

BTW, you do not actually manually focus--you do not even look through the viewfinder. In our above example, you simply align the distance mark for 1 meter when shooting @ f8, 10mm--that is all.

Clearer than mud yet?

Last edited by Jewelltrail; 12-12-2010 at 05:19 AM.
12-09-2010, 09:34 PM   #929
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soppy: I believe you essentially treat the lens like a prime once you get the wideness you want through the focal length. Then you must simply walk to where the subject is in focus, otherwise you would ruin the hyperfocal distance. This is just a guess of course, as I am pretty confused about the whole thing anyways.
Sorry for the confusion--we will resolve this--bear with me.

You still use the zoom like you always did. Once you select an aperture and focal length, then move the focus ring to the correct hyperfocal distance and you are Golden--it is that simple.

If you look at your 10-20 lens, just between the zoom ring & focus ring, you will see 2, vertical white lines. You simply align, in our example, the 1 meter/3 feet mark of the focus ring, with this line.

It is one of those things in life which sounds painful when you read about it--doing it is actually simple. If you dislike math, there are online charts which will do all the calculations for you--all you do is plug in the variables.

BTW, photographers often use the hyperfocal distance, on wide to normal FLs, when they want assurance they have maximum depth of field. The application is not so useful for telephoto lenses.

In summary, the only difference using the hyperfocal distance is, instead of using AF with the shutter button, you move the focus ring to max focus point(hyperfocal distance) first--then you trip the shutter button--obviously you must be in Manual Focus.

If you Google this, I'm sure you will get tons of hits, with other words to convey the same message which might help. Best of luck. Do not hesitate to ask another question though.

Last edited by Jewelltrail; 12-09-2010 at 11:20 PM.
12-10-2010, 03:53 AM   #930
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QuoteOriginally posted by Franki55 Quote
Sorry my English is not very good

Apollo Bridge on The Danube in Bratislava , Slovak Republic
is very most photography Architecture in City , is very Photogenic


My version " Negative colors "
awesome pic
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