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Old Oct 6, 2004, 1:57 PM   #1
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Greetings all,

I have the powershot A95 from Canon and I just got back from an anime con and the quality is not where it should be. I think it was because I was using ISO 50. I was using the largest size resolution and it was set to the finest quality but the pics out doors were a tad soft and indoors the pics were blurry.

What is the best allround ISO setting for indoor and outdoor portrait shooting?

Thanks,
Joe
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Old Oct 6, 2004, 2:40 PM   #2
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Joe:

There is no "best all around ISOsetting". The ISO speed needed will depend on the lighting.

The camera must keep the shutter open long enough for proper exposure of the images. ISO speed controls the sensitivity of the camera to light. Basically, it's amplfying the signal from the CCD more as you increase ISO speed.

You'll have the lowest noise (similar to film grain) at ISO 50. However, this will also be where you'll have the slowest shutter speeds.

So, if you tried to take photos in lower light without increasing ISO speed, you'd end up with motion blur from camera shake and/or subject movement (unless you are using the flash, or a tripod with a stationary subject).

This is most likely why your indoor pictures were blurry. What is bright to the human eye, is not to a camera's lens. Although it would be nice if we could keep ISO speed set low indoors without a flash or tripod; shutter speeds would be far too slow.

Each time you double the ISO speed, the camera can use shutter speeds twice as fast. As a general rule, just to prevent motion blur from camera shake, you need shutter speeds of 1/focal length or faster. In other words, at full wide angle (least amount of zoom) on your model, which is equivalent to 38mm on your camera, you'd want shutter speeds of 1/38 second or faster. At full zoom (equivalent to 114mm on your model), you'd want shutter speeds of 1/114 second or faster. This is because blur from camera shake is magnified greatly as more zoom is used.

So, with most models, the exposure algorithms are designed to automatically increase ISO speed if the shutter speeds are too slow as light is lower (to a point), using the Auto ISO setting. This helps to reduce blur from camera shake (but not from subject movement). The shutter speeds needed for a non-stationary subject may be even higher than the camera would select.

Now, if you use flash, shutter speed is not as critical. This is because the short flash burst has the effect of freezing the action (when you are within the flash range).

The lighting in most home interiors only has an EV (Exposure Value)level of around6 (sometimes lower at night, sometimes a little more in daylight). So, indoors without a flash, in typical lighting, at ISO 50, you'd need shutter speeds of around1/4 second with your model for proper exposure without the flash at your len's wide angle position. This is far too slow to prevent blur unless you're using a tripod.

So, you'll need to increase ISO speeds to around 400 to get shutter speeds up to around 1/30 second (probably close enough if your subject is not moving and you don't use zoom). But, you'll have very high noise levels at ISO 400.This is only a rule of thumb.Some users can hold a camera steadier than others.

Using zoom is different. Your model's lens is more than twice as bright at wide angle, versus full zoom. So, I'd try not to use zoom unless you have to indoors.

Basically, you'llwant to use your flash indoors to prevent excessive noise and/or motion blur, unless you want to use a tripod, and are taking photos of stationary subjects.

ISO 50 will have the lowest noise levels. But, as you can see, it also has it's downside (slower shutter speeds). Your flash range will also be greater at higher ISO speeds (each time you double the ISO speed, your flash range will increase by a factor of 1.4x).

Your model does not support an external flash from what I can see. I'd use a tripod whenever possible to reduce motion blur if you want to keep the ISO speeds set lower and don't want to use the flash. You may also want to look into better lighting for indoor photos and/or slave flash (designed to fire at the same time the camera's main flash fires) if more even lighting is needed.

If you do need to increase ISO speed in some conditions, you can also find tools to reduce the appearance of noise. Here are a few:

http://www.neatimage.com

http://www.picturecode.com

http://www.imagenomic.com

Personally, with your camera, I'd just keep it set to Auto ISO or ISO 100using the flash indoors, staying within the flash range, and removing the redeye later with software. It's not really designed for "existing light" shooting indoors without a tripod or flash (as is the case with most small cameras).
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Old Oct 6, 2004, 11:30 PM   #3
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JimC, maybe you can answer this. How does auto ISO setting work? I've always assumed that the lowest ISO is selected, until a certain shutter speed is reached (what speed?) and then the next ISO is selected. If this is the case, auto ISO would be OK for most situations, except for when a low shutter speed is acceptable or desirable. Is this your understanding?
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Old Oct 6, 2004, 11:41 PM   #4
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muskrat sam wrote:
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JimC, maybe you can answer this. How does auto ISO setting work? I've always assumed that the lowest ISO is selected, until a certain shutter speed is reached (what speed?) and then the next ISO is selected. If this is the case, auto ISO would be OK for most situations, except for when a low shutter speed is acceptable or desirable. Is this your understanding?
It's going to vary by camera model. Usually, if the camera is already selecting the largestavailable aperture for any given focal length, and shutter speeds fall below the reciprocal of focal length (1/focal length) rule of thumb for hand held photos, then most models are going to increase ISO speed. However, most will only increase it to a point. Even if a camera has an ISO 400 setting, the Auto ISO may only go to 160 or 200 in many newer models (to keep noise levels down, since higher ISO speeds often have very objectionable noise).

Each manufacturer may handle it differently. Many may even automatically boost it when light is low enough for a Flash indoors (which also helps out flash range).

To see what a given model will do, you'd really need to test it's behavior -- taking photos in a variety of conditions and viewing the EXIF to see what settings it used.

Many image editors can see the EXIF (a header in the image files containing camera settings used for a photo). If you don't have an editor that can look at it, download Irfanview from http://www.irfanview.com (it's free). Make sure to download the free plugins, too. The EXIF can be seen under Image, Information, EXIF.
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Old Oct 17, 2004, 11:24 PM   #5
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Greetings again,

I seriously can't get a quality picture from my A95. I think it got damaged in shipping or something.

Enclosed is a one of the better pics I've been able to take with it.

Camera on tripod and I pressed the shutter and even with my dad holding the camera the picture is real soft.

HELP!!!
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Old Oct 18, 2004, 12:39 AM   #6
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Joe:

You may want to try a few things:

* Make sure you aren't too close to your subject. The sample you posted looked like it may have been cutting it pretty close on the focus distance (a minimum of 1.5 feet at full wide angle, unless you are in macro focus mode).

* Make sure you are getting a focus lock (half press the shutter button down, and make sure you get a steady light, and your subject is in the selected focus point) before pressing the shutter button the rest of the way down. You may also want to try Center AF versus AiAF (available in your menus when in record mode), just to make sure the camera is trying to focus on what is in the center of the frame.

* Try resetting your camera to factory defaults. I'm not sure if the A95 is the same way or not, but with some of the older A series models, you could press and hold the menu button down for more than 5 seconds, and the camera would prompt you if you wanted to reset it to defaults.


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Old Oct 18, 2004, 1:22 AM   #7
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JimC - Ihave taken pics with my subjects at up to 10 feet away with the same effect and the only thing I changed in the settings is the largest resolution and set it to superfine. other than that it's factory spec.

Outdoors the pics look a lot better but indoors the pics are not up to par.

I just reset it to factory spec and changed the resolution to super fine and 2592 x 1944 and at 10 sec timer the pics still look bad and here is a pic at 640 x 480 mode in super fine.
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Old Oct 18, 2004, 9:23 AM   #8
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That one looks much better from a focus perspective (although, if you are using the self timer, you can't really tell if it's getting a focus lock or not).

Also, shooting at 640x480 may not be quite as good (depending on how well the camera downsizes images). My current pocket camera takes terrible photos at 640x480 (the downsizing algorithms don't work well in camera.

As for the background being dark, that's very normal (even in a better lit room). The camera must throttle down the flash strength to prevent overexposing the subject. Because there is a lot of difference between the light of the flash, and the light in the background, the background isgoing to be much darker.

Unlike the human eye, the camera has a limited dynamic range (ability to capture both light and dark areas of an image). What looks bright to us, is not to the camera.


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