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by Bart Arondson

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I've bought a Powershot sx20 half a year ago and I'm quite happy with it although I know it doesn't compare to a DSLR.

I've learning photography on my own: bought a 58mm ring and some filters (cpl, nd8, macro, star cross). I've got chdk to save in RAW so later with Photoshop I can reduce the noise of the pictures (and also use post-processing techinques to enhance them), and I'm using chdk's histogram to check if the picture has a good range. But there are some concepts I'm not fully understanding:

1) Aperture priority: even in the widest range mode, where it has from 2.8 to 8, I don't see any difference in the picture. I know that AP is used for DOF, and that P&S have huge DOF because of the sensor size, but then why is this mode here? What's supposed to do in a P&S?

2) Manual Focus: the slider goes from 0cm to infinity (Depending on the zoom) and even you have the option to see a zoomed zone in the center of the picture for a refined focus, I don't see much difference between little steps. May it be because it's an electronic viewfinder instead of optical?

3) Exposure: I've read that you should get a proper exposure. There is an indicator that warns me if the picture is going to be too dark or too bright, but the only options I have to change the exposure are the shutter speed and ISO, which I always try to be at 100 in order to avoid noise (of course during daylight or in a well-lit room). How can I know if it's really proper? Right now I have a post processing plugin in photoshop which does exposure compensation so I'm checking how much does the picture change.

Thanks, I hope these questions are clear enough.

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These are fine questions but they're different enough that they might be better posted separately. –  mattdm Mar 30 '11 at 21:00
    
Also: the first question is answered here: photo.stackexchange.com/questions/9240/… –  mattdm Mar 30 '11 at 21:03
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I would agree to your assessment for #1 and #2. As for #3, I would certainly recommend that you get a book or do some online research to learn about exposure, how to control it, what constitutes "good" and "bad" exposure in various types of photography. I would also encourage you to look into artistic books or online tutorials that teach you about the more subjective (i.e. eye of the photographer) type stuff. –  jrista Apr 14 '11 at 4:29
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I was trying to get the book "understanding exposure". Do you think that's a good one? –  Luciano Apr 14 '11 at 13:02
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@Luciano - yes, its a great book –  rfusca Apr 14 '11 at 22:05

1 Answer 1

up vote 1 down vote accepted

1) Aperture priority: even in the widest range mode, where it has from 2.8 to 8, I don't see any difference in the picture. I know that AP is used for DOF, and that P&S have huge DOF because of the sensor size, but then why is this mode here? What's supposed to do in a P&S?

You are correct in saying that a P&S has a huge DOF, however on these types of cameras the Av mode is often used as an alternative for Macro (little flower icon) mode. Having the aperture wide open is a common characteristic of Macro photographs.

2) Manual Focus: the slider goes from 0cm to infinity (Depending on the zoom) and even you have the option to see a zoomed zone in the center of the picture for a refined focus, I don't see much difference between little steps. May it be because it's an electronic viewfinder instead of optical?

I'd definitely agree that it's far more difficult to see focus adjustments on an LCD (the electronic viewfinder) rather than an optical eyepiece. Again, it's not an entirely useless feature, but rather a more advanced version of a possibly pre-existing function. Setting focus in manual on your P&S would be useful when shooting landscapes (the mountains or hills icon, normally) or again if shooting Macro (little flower).

3) Exposure: I've read that you should get a proper exposure. There is an indicator that warns me if the picture is going to be too dark or too bright, but the only options I have to change the exposure are the shutter speed and ISO, which I always try to be at 100 in order to avoid noise (of course during daylight or in a well-lit room). How can I know if it's really proper? Right now I have a post processing plugin in photoshop which does exposure compensation so I'm checking how much does the picture change.

I dare say the comments above handled this nicely: read up, research. You'll understand it, it's something all photographers have to wrap their heads around.

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I'm going to accept this answer since it answers the questions and complements very well with the comments above. I'd really like to thanks the commenters as well for their insights. –  Luciano Apr 18 '11 at 12:17

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