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Old Apr 1, 2003, 6:06 PM   #1
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Default smaller aparture or low light focusing

Iam trying to use G3 for portrait photography. I use external studio flash fired by slave units.G3 in manual mode I select shutter speed 125 and aparture 8.Even then i get over expose.Is it possible to have a smaller opening say aparture 16,24,32 etc??.With ND filter ON the shots come correctly but due to very low light cannot focus. any sugetion to focus in very low light or else how to make a smaller aparure ??.Even by reducing flash power it dont work.

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Ali
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Old Apr 1, 2003, 7:25 PM   #2
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Default Re: smaller aparture or low light focusing

Quote:
Originally Posted by kondath
...Is it possible to have a smaller opening say aparture 16,24,32 etc??.
No, diffraction starts depending on the physical size of the aperature. Since consumer digicams have a real focal length something like 1/5th of their equiv focal length, the aperature is a bit over two stops smaller for the same physical size. Since the smallest f/stops on 35mm cameras is typically f/16 (or f/22 on real long lenses), the smallest f/stop on a digicam would be a bit under f/8 (f/7.16 to be closer) to have the same physical aperature.

If you haven't done it yet, I'd suggest taking a close look at the EXIF data to make sure the camera settings are what you think they are.
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Old Apr 4, 2003, 10:33 PM   #3
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Beware, beware...The design of the ccd chip,unfortunately, creates havoc with tiny apertures. At the smallest aps, difraction bends the light enough (iris diameter + ccd size + incident element dimensions) to create chromatic aberations at these settings.
My experience has been that blowing up a 5mp image to a 13X19 print, shows these problems; especially in even toned photos. Mid range aps seem to give better results. Try it yourself.
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Old Apr 5, 2003, 10:52 AM   #4
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Default Re: smaller aparture or low light focusing

Quote:
Originally Posted by kondath
I select shutter speed 125 and aparture 8.Even then i get over expose.
Okay, I'm not a professional, but wouldn't a faster shutter speed be the solution? 1/125 of a second is awfully slow compared to the speed even I can get on my Oly D-370 (1/2000)

Assuming you can get at leat 1/1000, you could effectivly go 2 stops darker.

Am I making sense?
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Old Apr 5, 2003, 12:04 PM   #5
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Quote:
Assuming you can get at leat 1/1000, you could effectivly go 2 stops darker.
NO! You said you were using flash, the duration of a flash is a lot less than 1000th sec, so any shutter speed just lets in more background illumination and if tungsten, gives mixed light white bal probs.

I'm not a pro., but if you are doing portraits, isn't your cam on a tripod, so why can't you use manual focus or doesn't the G3 have that? (I'm not a G3 owner either) Is there a 'portrait picture scene' option what sets focus to short distance?. The ND filter on the lens is a good idea, so is reducing the effective ASA in the cam. Are your slaves firing on auto? They seem a bit powerful, can their output be controlled or moved further back.

Hanging ND in front of the flash only works if you have manual settings on the flash, or can you set the manual settings so the flash fires less power: eg tell it your using BIG ASA or a few feet distance or bigger f stop than you really are.
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