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01-03-2011, 04:30 PM   #31
Ira
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QuoteOriginally posted by Mike Cash Quote


That's not an analogy; it's a scenario.
The definition of an analogy relates to "comparisons," as do the comparisons of this ISO versus that shutter speed versus this F stop directly relate to photography. As does an analogy of shooting at 100 ISO in bright sun compared to 800 ISO in heavy clouds.

The bank robbery aspect just makes the analogy more interesting.

Because when that happens, I doubt the OP will find a seesaw around.



01-03-2011, 05:57 PM   #32
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QuoteOriginally posted by Ira Quote
The definition of an analogy relates to "comparisons," as do the comparisons of this ISO versus that shutter speed versus this F stop directly relate to photography. As does an analogy of shooting at 100 ISO in bright sun compared to 800 ISO in heavy clouds.
Still not an analogy...closer to an allegory, perhaps.


QuoteQuote:
Because when that happens, I doubt the OP will find a seesaw around.

Certainly not one with three ends. No doubt about that.
01-04-2011, 09:49 PM   #33
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QuoteOriginally posted by Ira Quote
We sometimes forget how what we consider a simple concept really isn't.

Four, a higher ISO lets you use a faster shutter speed (which lets in less light than a slower shutter speed), OR allows you to use a smaller F stop (which lets in less light than a larger F stop).

Or both.

You have to decide first:

1) "Wow! Plenty of sun today! I'm gonna keep the camera on 200 ISO for the least noise and best image quality!" (200 needs more light than 400, but you don't care. It's sunny, remember?)

2) "Look at this gorgeous flower! And gee, I love automatic mode! I'm in Av mode, I have my F stop set for F8, and the camera is giving me a shutter speed of 1/125! That shutter speed is plenty fast for me to handhold the camera, and that flower isn't doing much moving! Click! I got a great shot here!"

3) "Uh oh! Where did all those clouds come from? What happened to the sun? Damn! I still want to take more shots of that flower! But now it's giving me a shutter speed of 1/30, which is too slow for me to handhold since my hernia operation! Plus, the wind is moving the flower a little and 1/30 won't freeze it for a sharp picture! DAMN YOU NATURE! I want to stay at F8 for the better depth of field, but wait--all I have to do is change my ISO higher and see what I got. Let me try 400. HOORAY! It worked! The higher ISO allowed me to stay at F8, and is ALSO giving me a shutter speed of 125! GOD BLESS YOU PENTAX!"

4) "What's that!? They're robbing the BANK!!! And here I am with my camera! But those clouds are still here!!! And those guys are running FAST!!! I just need the shot! What to do!? What to do!? Wait--I remember what Ira told me! Let me set it for the highest ISO I have! Let me go to F4 to let in more light to be even safer. I don't care about noise in this image or even a little less depth of field, because I just want the shot to sell to the newspaper! CLICK! I did it! Perfectly exposed! I'm famous!

"But Ira deserves all the credit!"
The really sad thing is that this makes sense to me. Ira, you're a nut

Richard.
01-05-2011, 11:24 AM   #34
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got to say it aswell Ira, it made sense to me infact I think thats when the penny really dropped! Thankyou

01-06-2011, 12:17 PM   #35
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QuoteOriginally posted by Ira Quote
"But Ira deserves all the credit!"
You do! ROTFLOL!!!
01-06-2011, 03:05 PM   #36
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Thank you, ladies and gentlemen. Thank you. Please. No more applause. Please take your seats.

But seriously folks, to me, this is what it's all about, and why I ALWAYS recommend manual ISO--never auto--even if you're in an auto shooting mood like Av:

You just have to look up at the sky or the building you're in to get a feel for the right ISO to be using in a given situation. Bright, bright sun--you KNOW you're golden at ISO 100-200. Overcast, 400. Really dark and funky, the sky's the limit.

And you know that you HAVE to shoot at a specific aperture and/or shutter speed for the subject at hand. So the aperture and shutter speed come FIRST, and if it hits the target at your selected ISO, you're golden. Otherwise, change the ISO.

Another example:

You can be outdoors in bright sun, non-moving subject, and you've selected--or you have auto ISO enabled--and it gave you an image shot at 1/500th of a second, F16, ISO 800.

Not only is 1/500th not needed, this combination gave you F16 (a bad part of your lens for IQ), and 800 is horrible compared to 200. (800 is still okay on today's Pentaxes, but only when you really need it.)

It's a matter of compromises and judgments based on what you're shooting, but for the above example, ISO 400 (1 stop different from 800), 1/250th (1 stop difference from 1/500th), would result in an F stop of F8 (two stops difference from F16), and F8 is a much sweeter spot on all lenses than F16. (And yeah--depth of field is a different issue.)

So even though both combinations above give you the same proper "exposure," the latter one gives you a much cleaner/less noise image ISO at 400...a shutter speed that's just fine at 1/250th...and much better IQ for your lens at F8 as opposed to F16.

I guess the point I'm trying to make is that while all examples of this "math" can all result in proper light exposure in relation to metering alone, there's a BIG difference in your final image based on your decisions on which math you decide to use as it affects each of the three elements--ISO, shutter speed, F stop.

Last edited by Ira; 01-06-2011 at 03:12 PM.
01-06-2011, 05:36 PM   #37
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Manual ISO may be ideal, but a great compromise is Auto ISO limited to 100-400.

I do almost all my shooting in Av, ISO 100-400, take a quick peek at the shutter speed in the viewfinder while composing. If the shutter speed is inadequate my first move is a re-think of my selected aperture, then I'll bump the ISO if I absolutely have to. This on a K200D where 800 is usable and 1600 is a bit of a disaster.

I'd expect the same methods can be employed in the magical new bodies, but with the range limited to 1600 on the high end for safety's sake.
01-06-2011, 08:11 PM   #38
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Well, what do you want to do with the iso file? if you want to put it into dvd, you need to exacted the iso files to the actul videos, hope it could help you!

01-06-2011, 11:52 PM   #39
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QuoteOriginally posted by grainbelt Quote
Manual ISO may be ideal, but a great compromise is Auto ISO limited to 100-400.

I do almost all my shooting in Av, ISO 100-400, take a quick peek at the shutter speed in the viewfinder while composing. If the shutter speed is inadequate my first move is a re-think of my selected aperture, then I'll bump the ISO if I absolutely have to. This on a K200D where 800 is usable and 1600 is a bit of a disaster.
That's what I do most of the time with my K200D, with occasional bold ventures into Tv land when things start to move around.

QuoteOriginally posted by grainbelt Quote
I'd expect the same methods can be employed in the magical new bodies, but with the range limited to 1600 on the high end for safety's sake.
I've been using manual ISO on my K5 very much the way Ira talks about a few posts ago. I tried auto ISO today when I went for a walk around 6:30am. I've got the full range (80 - 51,200) set in the menu. So far it hasn't wanted to go above 400.

Richard.

Last edited by RichardS; 01-07-2011 at 12:04 AM.
01-07-2011, 12:35 PM   #40
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QuoteOriginally posted by Jiscca Bally Quote
Well, what do you want to do with the iso file? if you want to put it into dvd, you need to exacted the iso files to the actul videos, hope it could help you!
See, this is why we should have kept using ASA. (When I hear DIN, I think of connectors, and the numbers are weird.)
01-07-2011, 04:48 PM   #41
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QuoteOriginally posted by Just1MoreDave Quote
See, this is why we should have kept using ASA. (When I hear DIN, I think of connectors, and the numbers are weird.)
I wondered if anyone would pick it up

DIN is just the German Standards Organisation (Deutsches Institut fur Normung) and they have standards for lots of things. My old rangefinder camera has ASA and DIN on its lightmeter, so no confusion there. It's German, so that might have something to do with it.

Richard.
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