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Old Oct 9, 2006, 7:57 PM   #11
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You'll see the aperture ratings of a lens in it's specs (and it's also printed on the front ot the lens).

Your lens is rated at f/2-2.5 (f/2 is available at the wide angle zoom setting, and f/2.5 is the largest aperture available at the maximum zoom setting).

Most zoom lenses start out with a maximum available aperture of f/2.8 at the wide end of their zoom range (and your Canon's G2 has f/2 available, which is twice as bright as f/2.8 ), and drop off to a smaller available aperture (higher f/stop number) on their long end.

Aperture when expressed as f/stop is a ratio between the focal length of the lens and the area of the iris opening diameter.

With a prime (non zoom) lens, you will see one aperture listed.

With a zoom lens, you usually see two apertures listed (the largest available aperture at wide angle zoom setting, and the largest available aperture at the full telephoto zoom position). When in between the widest and longest focal length of the lens, the largest available aperture will fall somewhere in between the apertures shown in the specs (and printed on the lens).

Some higher quality zoom lenses can maintain a constant aperture throughout their zoom range (with f/2.8 being the most common). But, most lose some brightness as more optical zoom is used. Some of the smaller subcompacts may drop down to an aperture as small as f/4.9 or f/5 (an f/2.8-4.9 lens is relatively common). Most ultrazooms are a bit better than the run of the mill compact models (but, your G2 still beats them for lens brightness).

When you vary the aperture, you're controlling the iris in the lens (which like a pupil in your eye, can be opened up to let in more light or closed down to let less light in).

So, this impacts the shutter speeds you'll need for proper exposure (since more or less light is getting through to the sensor).

In low light, the camera will already be opening up the aperture to it's widest setting (lowest available f/stop number). In bright light outdoors, it may close it down some (smaller iris opening = higher f/stop number).

The aperture scale in one stop increments (with larger than f/1 apertures theoritically available) goes f/1.0, f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0, f/11, f/16, f/22... With each one stop move to a smaller aperture (represented by higher f/stop numbers), you will need shutter speeds twice as long for proper exposure for the same lighting and ISO speed.

Take a look at this handy calculator to give you an idea of how the relationship between light levels, aperture, ISO speed (shown as film speed in the calculator) and shutter speed works. Your Canon is probably about 1/3 stop more sensitive than it's rated ISO speed (which represents how senstive the film or sensor is to light)

http://www.robert-barrett.com/photo/...alculator.html

If you look at the bottom of the page, you'll see a graphic representation of a camera's iris opening and closing with your settings. You can set the calculator to use 1/3 stop increments, too.

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Old Oct 9, 2006, 8:05 PM   #12
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Excellent, thanks!
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Old Oct 9, 2006, 8:29 PM   #13
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Try your camera and see what you get for shutter speeds in the lighting you're gong to shoot in with the ISO speed set higher.

If you can get your shutter speeds up to around 1/50 second (which is probably about where they'll be at ISO 400 with your lens in typical indoor lighting), you should get a relatively high percentage of keepers if you take lots of photos and your subjects aren't moving too much.

Be careful about holding the camera steady while you're squeezing the shutter button, too (as you can get some blur from camera shake if you're not careful or using a tripod).

You won't stop all motion blur from subject movement in typical indoor lighting. But with shutter speeds 8 times as fast using ISO 400 as you were getting at ISO 50, you should see a huge improvement. ;-)

If light is not good enough for what you need at the print and viewing sizes you'll use (and noise, blur, etc, are not as noticeable at smaller sizes), then I'd look at a model that lets you shoot at ISO 1600 or higher that has a lens that can maintain f/2.8 throughout most of it's focal range. In non-DSLR models, the newer Fuji models typically have higher usable ISO speeds.

Don't even bother to look for a lens as bright as your G2's. The newer digicams that can shoot at higher ISO speeds compared to your model won't have a lens that bright. They don't put zoom lenses that bright on any of the newer cameras.

Even within the G series, Canon decided to go with a dimmer lens with it's new G7 model (and although the G6 had a lens that started out as bright as the one on your G2, it didn't give you higher ISO speeds than you already have).

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Old Oct 10, 2006, 7:06 AM   #14
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Quote:

Will a bigger lens give me better lowlight action shots?

If this is true; then the huge lens of the R1 will be the best LOL!



Sony Cyber-Shot DSC-R1.

JimC has been very informative and I don't wish to repeat everything he has said. :-)

An F/1.4 lens will be a great low light lens though. (F/1.8 and F/2.8 lenses are also fast) :idea:

The Pentax *istDS& the Pentax *istDS2have auto ISO 200 - ISO 3200 if I am not mistaken! (I know that the Pentax K100Dhave that feature!)

Code:
Auto sensitivity setting


Like many digital compact cameras, the *istDS2 features an "AUTO" position for sensitivity setting. In this position, the camera's sensitivity is automatically set by the camera, based on such factors as subject brightness and lens focal length, while the user can randomly select the upper limit of sensitivity between the standard output of 400 and 3200. This position is extremely useful to avoid camera shake in poorly lit locations and to prevent sensitivity resetting failures by the photographer.
Code:
Auto sensitivity control up to 3200 standard output sensitivity

The K100D features an auto sensitivity control function, which automatically sets the optimum standard output sensitivity — up to 3200, which is the highest automatic setting in its class — based on such data as the subject's brightness level and the lens' focal length. Since this function allows the use of higher shutter speeds in poor lighting situations (such as indoor sports events and night scenes), it helps the photographer to effectively reduce camera shake and prevent blurred images.


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Old Oct 10, 2006, 3:54 PM   #15
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Lets consider the Moneys-No-Object aproach to your specific situation.

Buy a DSLR and a 85mm f/1.4 lens (Not Cheap).

Your current ISO400 F/2 1/20 settings = LV4, so with the new lens ISO1600 F/1.4 1/125 = LV4 (you need that shutter speed to stop camera shake).

That means you'd still be at the absolute extents of what that setup can do. The results would be good, plenty acceptable, but at the limits nonetheless. If you wanted a zoom it would be f/2.8 because thats as fast as they come, and you'd be unable to make sharp pictures still unless you got an image stabilized version, but then subject movement would probably be a problem.

You need MORE LIGHT!
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Old Oct 10, 2006, 3:56 PM   #16
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Funny coincidence, I just opened this link talking about this very problem.
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Old Oct 10, 2006, 5:29 PM   #17
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Great article. Thanks, tmoreau.
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Old Oct 10, 2006, 10:03 PM   #18
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(I didn't read all the replies carefullly so this may be redundant)

To answer the question, generally yes.

A faster lens (with a smaller f-stop number at maximum aperture) allows shooting at lower light levels at higher shutter speeds. All other things being equal, a faster lens is probably physically larger.


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Old Oct 11, 2006, 11:54 AM   #19
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You might need above ISO400, as high as ISO1600 perhaps.
Only SLRs go that high.

Also, try increasing exposure compensation.

get the Kodak P712 for $400, or the P880.


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Old Oct 11, 2006, 12:22 PM   #20
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Quote:

You might need above ISO400, as high as ISO1600 perhaps.
Only SLRs go that high.

WRONG! :blah:

The Canon PowerShot G7, Canon PowerShot SD900, Canon PowerShot SD800 IS, Fujifilm FinePix F31 fd, Fujifilm Finepix S9100, Fujifilm FinePix S6500fd, Fujifilm FinePix F20 Zoom, Fujifilm FinePix Z3, Fujifilm FinePix F30 Zoom, Fujifilm FinePix Z2, Fujifilm FinePix F11 Zoom, Fujifilm FinePix S5200 Zoom, Fujifilm FinePix S9000 Z, Fujifilm FinePix F10 Zoom, Fujifilm FinePix V10 Zoom, Leica D-LUX 3, Leica V-LUX 1, Leica C-LUX 1, Olympus SP-510 UZ, Olympus Stylus 1000, Olympus Stylus 750, Olympus Stylus 740, Olympus Stylus 730, Olympus Stylus 725 SW, Olympus Stylus 810, Olympus Stylus 720 SW, Olympus Stylus 700, Panasonic Lumix DMC-FZ50, Panasonic Lumix DMC-LX2, Panasonic Lumix DMC-FX3, Panasonic Lumix DMC-FX50, Panasonic Lumix DMC-FX07, Panasonic Lumix DMC-TZ1, Panasonic Lumix DMC-FX01, Panasonic Lumix DMC-FZ7, Panasonic Lumix DMC-LZ3, Panasonic Lumix DMC-LZ5, Ricoh Caplio R5, Ricoh Caplio 500G, Ricoh Caplio GX8, Ricoh GR Digital, Sigma DP1,Sony DSC-N2, and theSony DSC-R1 all have ISO 1600 or higher. Some of them even reached the ISO 3200 - ISO 6400 level. (And all of them here are non dSLRs)

Regards.
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