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Old Aug 21, 2006, 1:21 AM   #1
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Hello all,

I'm a real novice photographer and this is my first post on this forum. I recently bought the 8MP Olympus SP-350 and I was wondering if anyone could explain to me what are these lense characteristics for my camera 8.0 - 24.0 mm and 1:2.8 - 4.9 .

The first one, 8.0 - 24.0 mm,has to do with the 3x ZOOM???What are this "mm" measuring?

The second one, 1:2.8 - 4.9, I'm not surewhat it is. I guess it has to do with the aperture range of the lense, butacording to the specifications in the instruction manual the aperture value isf2.8 - f8.0.

...and finally are these charateristics on my camera good? What is better 8.0 - 24.0 mm or 34 -102 mm like my old HP 720 Photosmart? The smaller the mm the better?

The same for the other thing. What is better 1:2.8 - 4.9 or 2.6 - 4.5?

Thank you very much in advance.

Sop.
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Old Aug 21, 2006, 4:59 AM   #2
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8-24mm refers to the actual focal length of your lens. At it's widest angle it is an 8mm lens and at it's 'most zoomed' it is 24mm. The angle of view the lens gives depends on the sensor size and these measurements probably give an equivalent of a 34-102mm lens on a 35mm film camera. If your HP photosmart was a digital camera then it is very unlikely that it had a 34-102mm lens. It probably had a very similiar lens to the one on your new camera, one that gave a 35mm equivalent of 34-102. Larger numbers are better as they represent larger lenses that capture more light. However, you then need a larger camera for the larger lenses. This is one of the things that make dslrs and high-end point and shoot cameras better - they let more light in and have a greater surface area of sensor to capture it on. The downside is they are bigger, heavier and more expensive.

1:2.8-4.9 probably refers to the widest aperture. At 8mm focal length the aperture can open to f2.8 but at 24mm it can only open to f4.9. Lower numbers are better. Your new lens is faster at it's wide angle but slower at full zoom. Not much difference though and other factors in both lens and camera are likely to be far more important here.

f2.8-f8 likely refers to the widest and smallest apertures the lens is capable of, which suggests that this lens cannot provide a smaller aperture than f8 at any focal length. With a lens this small at f8 the aperture is probably already near pinhole size and any smaller would cause diffraction problems (and is probably of little use anyway as you would already have a huge depth of field).
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Old Aug 21, 2006, 1:40 PM   #3
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Thank you very much for your reply it was very explanatory. I have also been reading some articles over the internet and learned a bit in the last 24 hours.

I want to take photos at night with my Olympus SP-350, and considereing its specs and to get the best quality out of my camara I have saved this settings. I don't care about shutter speed since I will be photographing mainly buildings, monuments and landscape (and they don't move LOL), so if I have to wait 10 senconds or more it is OK. What I want is the best photo quality possible. Here are the settings:

ISO: 50 to reduce noise levels.

Aperture value: f8.0 to have a greater "deep of field". Am I right here or should I use a higher aperture f.2.8?

Shutter speed: I will let the camera set this in auto, but taking into consideration the previous two settings I guess it would be a long exposure to get the availble light, am I right?


Since I wll be most likely needing long exposures, my main problem will be camera shaking, so this other things I will be using:

- Tripod, to avoid camera shake.

- Self timer,to avoid camera shake when pressing the shutter.

- Turn the flash off.

- Noise reduction feature.

- Try to avoid using the ZOOM. to avoid camera shake as well.

What do you think about my settings?

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Old Aug 21, 2006, 2:22 PM   #4
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jacks wrote:
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1:2.8-4.9 probably refers to the widest aperture. At 8mm focal length the aperture can open to f2.8 but at 24mm it can only open to f4.9. Lower numbers are better. Your new lens is faster at it's wide angle but slower at full zoom. Not much difference though and other factors in both lens and camera are likely to be far more important here.
Actually, that's a lot of difference (but, these specs are typical for most compact cameras), unless you're just talking about the difference between the two camera models mentioned.

f/2.8 is approximately 3 times as bright as f/4.9.

So, in low light, for any given ISO speed, you'd need shutter speeds about 3 times as long for proper exposure shooting at your camera's longest zoom setting (most apparent magnification) versus it's widest zoom setting (least apparent magnification) with the aperture wide open (and a camera's autoexposure algorithms are going to use the widest available aperture in low light anyway).

Not only does this light loss at longer focal lengths impact motion blur from camera shake and subject movement from slower shutter speeds, but the camera's Autofocus sensors can't see as well to focus (since only about 1/3 the light gets through at the longest focal length), impacting Autofocus speed and realiability.

Of course, blur from camera shake is also magnified as focal lengths get longer. So, slower shutter speeds can compound problems in low light if you're not using a tripod or flash.

If you're using a flash, this will also impact your flash range (which is why you see two ratings for flash distance with most compact cameras -- max range at the widest zoom setting, witih the range dropping off at longer zoom setting).

This difference in light gathering ability with many lenses as focal lengths get longer is one reason zoom lenses with a constant aperture (for example f/2.8 throughout their focal range) are desirable on DSLR models if you plan on shooting in lower light.

But, sometimes even f/2.8 isn't bright enough, so an even brighter prime can be a good thing to have. I tend to use primes (non zoom) lenses in low light indoors, since my brightest zoom lenses only have f/2.8 available to them and I've got brighter primes.

Basically, these types of constant aperture zoom lenses are actually opening the iris up wider as focal lengths get longer. If the aperture iris opening size remains the same, you'll see the largest available aperture (smallest available f/stop number) change with focal length, as it does with most zoom lenses.

That's because aperture, as expressed in f/stop is a ratio between the focal length of the lens and the area of the iris opening (even if the iris size doesn't change, the widest available aperture will change as focal lengths get longer with most zoom lenses, letting less and less through to the sensor or film as your focal length gets longer).

When comparing camera models for low light use without a flash or tripod, I'd keep this in mind.

For example, a camera with a lens that lets you select f/2.8 at a focal length equivalent to 100mm, would give you shutter speeds 50% faster at ISO 800, compared to a model shooting at ISO 1600 that has a lens with only f/4.9 available at the same focal length. ;-)

The aperture scale in one stop increments goes f/1.0 (theoritically larger apertures are availalbe, too), f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8, f/11, f/16, f/22, etc.

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, given the same lighting and ISO speed.

So, with compact cameras with a typical zoom lens that loses a lot of light as you zoom in more, it's a good idea to try and stay on the wide end of the lens in low light (use your feet for zoom instead). This helps autofocus speed and reliability, gives you faster shutter speeds if you're not using a flash, and increases your flash range if you are using a flash.


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Old Aug 21, 2006, 10:02 PM   #5
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"Actually, that's a lot of difference (but, these specs are typical for most compact cameras), unless you're just talking about the difference between the two camera models mentioned."

Yes, I was comparing the two lenses the op mentioned.
However, for some reason I read these as f2.6-f4.9 and f2.8-4.5 instead of as f2.8-4.9 and 2.6-4.5 so in fact the old lens is slightly faster throughout it's range though, once again, there isn't much between them.

Those settings look fine for night photography. By far the most important element is the tripod.
You don't need to avoid zoom if you are using a tripod (unless your tripod is very flimsy).
Also, sometimes flash can be useful, especially if you have something in the foreground. If you have a person in front of a lit building for example, the camera will likely expose for the building leaving the person very dark. Flash will light the person but the building will be too distant for the flash to have any effect and so it will still be correctly exposed.
I don't know about noise reduction but shooting in RAW (if possible) would give you the best chance of extracting everything you can from the shot provided you have, and can use, some decent editing software.
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Old Aug 22, 2006, 8:55 AM   #6
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Thank you both.

Yes my camera offers the possibility to save photos is RAW format but I have no idea how to edit them. My camera comes with its own software of course but why do RAW files need to be corrected? Do RAW files need to be edited always? or can I just print them as they come out?

Their size is huge as well. For a 8MP (3264 x 2448 ) shot:

JPG: between 3 - 4.5 MB

RAW: I think it was about 9 MB

Curiously the TIFF format files,which I am more familiar with, are even larger, I think 15 MB. Even if I convert them (the TIFF files) from smaller RAW format files. I always assumed RAW format had better quality than TIFF format, but TIFF format files are larger. Is that possible?

Also I have noticed that I can not open my camera RAW files with other software except the OLYMPUS software that comes with the camera. I always used Paint Shop Pro (is that good?) but I can not open RAW files with that.

Thanks again.



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Old Aug 23, 2006, 1:30 PM   #7
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No, you can't just print a raw file (or view it with most image editors).

When you shoot in RAW, as the name implies, the camera is storing unprocessed data from the sensor.

One advantage of RAW, is that you have a higher bit depth (more bits representing the color and brightness, and you canchange the settings for things like White Balance, Sharpness, Contrast, Saturation, etc., later using software.

For example, if you let the camera choose white balance settings for light you are working in, and the colors don't come out the way you anticipated, then this can be harder to correct later, because the data has already been processed by the camera. The camera's Auto White Balance tries to accurately determine the temperature of the light source, so if it gets it wrong, or if you have it set wrong, then it's difficult to correct later.

With RAW, you can set these things later using software, trying different settings to make it look "just right". Or, take contrast for example:If the camera processes the CCD data with contrast set to high, then you can lose detail in the photo. Or, if you have sharpening set too high, you can cause unwanted "halos" around sharper edges. You also have more exposure latitude with RAW.

It's not a standard image format. It's a file containing the data captured by the sensor with no processing of any kind yet, and the file format is unique to each manufacturer (even changing between different models with the same file extension). That is a problem in the industry, since most manufacturers don't publish the information on how they store this information. You can read more about this issue here:

http://www.openraw.org/info/

The invidual photosites in your camera's sensor are only sensitive to one color each, and with most Bayer Pattern CCD designs, you have twice as many sensitive to green.

The raw conversion algorithms take the values from the red, green, and blue photosites and combine them via sophisticated interpolation techniques so that all 3 colors are stored for each pixel. Basically, your camera is doing this same thing with it's image processing (it's a built in raw converter).

The raw file has not combined the photosites in any way.

That's what the raw conversion process does. There are a number of different algorithms used, and some are better than others. You can see some of the common ones discussed here (requires Adobe Acrobat Reader):

http://www.ece.gatech.edu/research/labs/MCCL/pubs/dwnlds/bahadir05.pdf

Because a TIFF file has already gone through this conversion process, it's got values for all 3 colors (red, green and blue) stored at each pixel location (interpolated from surrounding pixels). So, even though it's larger, it doesn't contain the same detail as the raw file. With a tiff file, the data from the sensor has already been processed. It's just not compressed like a jpeg file (which is a lossy compression format).

Most converters are doing some additional processing, too (sharpening, contrast, etc.), as is the image processing in your camera.

The raw file is more of a "digital negative" that hasn't been developed yet. A tiff or jpeg image has already been developed (and if this development did not get all of the data you want from the image, too bad, it's gone).

As far as products that can convert your files, you can find them. David Coffin has already published source code that knows how to read and convert the images from your camera (he's reverse engineered the raw files from just about every camera ever made that is capable of giving you a raw image).

If you look through the "Other Raw Decoders" section of his web site, you'll probably find that some of the products that use some or all of his source code also support your camera.

http://www.cybercom.net/~dcoffin/dcraw/

One popular free product that uses Dave's algorothms for the demosaic part is UFRaw (and it supports all of the cameras that dcraw.c does).

http://ufraw.sourceforge.net/


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