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08-10-2013, 12:38 PM - 1 Like   #1
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Sunny f/16... what is it for APS-C?

Back when (like WAY back when in film days), I had a rough rule-of-thumb for sunny daylight... 1/100 second using ASA 100 or 125 film, at f/16.

What is the aperture equivalent for Pentax APS-C sensors, like the one on my K-30? Again, let's assume I am using 1/100 second with ISO 100... and also that I do not want to use an aperture so small that it would produce diffraction effects.

Thanks!

08-10-2013, 12:47 PM   #2
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IT's still the same rule: as a starting point set the shutter speed to the ISO for an f16 aperture. To use a different aperture, just move the shutter speed the same number of stops: f16 at 1/100, f11 at 1/200; f8 at 1/400, f5.6 (often optimal) at 1/800, f4 at 1/1600.
08-10-2013, 05:03 PM   #3
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Thanks Jon....I was wondering the same thing. The camera meters are so good these days. Back in the day with the K1000, you were better off starting with sunny 16 and adjusting from there according to what you eyes perceived the exposure to be.
And thanks Tom for confirming
08-10-2013, 08:04 PM   #4
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@TomB_tx -- Tom, isn't there some kind of offset because APS-C is smaller than the old film 35mm full-frame? Does the old f/16 equate to our f/11, or f/8? And thanks for the help ... back when, was happily chugging along in physics class until we hit optics, full stop.

08-10-2013, 09:01 PM   #5
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QuoteOriginally posted by jon404 Quote
@TomB_tx -- Tom, isn't there some kind of offset because APS-C is smaller than the old film 35mm full-frame? Does the old f/16 equate to our f/11, or f/8? And thanks for the help ... back when, was happily chugging along in physics class until we hit optics, full stop.
Hi Jon,

I think you're getting confused with the "Image Equivalence" perspective -- using image quality criterion to compare different sensor formats. For exposure alone, nothing changes due to different formats. Sunny 16 works for any camera, any lens shooting any format.

This is a main gripe with the Image Equivalence supporters. Many commonly use f stop as if it's a measure of DOF instead of a convention for computing exposure and that's just confusing for many people. The perspective can be useful at times for comparing formats, but many people use it where it's not really relevant.

Scott
08-10-2013, 10:27 PM   #6
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Thanks Scott -- one less thing to worry about!

However, maybe you guys can advise me ... at f/16 on our APS-C cameras, will I get noticeable diffraction? I want as much depth-of-field as I can get, but not at the expense of sharpness. Imagine a landscape with some flowers in the near foreground, and some hills in the far background... can I use f/22?
08-10-2013, 10:56 PM   #7
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Hi Jon,

Everyone will probably have their own opinion, and some will depend on the lens used. I think you really have to experiment and judge for yourself. As you get to the smaller apertures, in landscape shots as well as something like macro shooting, there will be a point up to which gaining more DOF trumps sharpness, but it really can be different for different people. I try not to make hard and fast rules. For a while at least, try shooting the same scene at f11, f16, and f22 with the kit you have and see what pleases you the most. Keep doing this until you have a sense of how you want to shoot these scenes in the future. That's one of the beauties of digital -- you can experiment to your heart's content and the cost is minimal, if anything. No real need to take someone else's word for anything -- make your own rules.

Don't forget that you also have the option of sharpening, or even selectively sharpening any shot it PP. Sometimes you can overcome the weaknesses in the gear with skillful work in the "digital darkroom"

Scott
08-10-2013, 11:47 PM   #8
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Thanks Scott -- that's very good advice. And now (actually, tomorrow) I'm off to enjoy my new K-30! Downloaded the v.1.04 update earlier this evening, and away we go.

Missed a trick, though. President Obama came through here a few days ago... LA for the Tonight Show, and Camp Pendleton, our Marine base. Should have gone up and asked him to get the Chinese to make a K-mount autofocus <$200 f/2.8 400mm telephoto. Like if they won't, we'll take all their Buicks away. Oh well. Maybe next year!

08-11-2013, 01:26 PM   #9
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Due to the 1.5 factor (1 inch sensor vs 1.5 inch), you are enlarging the image more to get the same size as FF--the difference is about equivalent to 1 stop in resolution or about square root 2 (1.414 vs 1.5)--so if you are happy w/ f/16 on FF, then you would use f/11 on 1.5x reduced sensor. But it depends on what size you are printing to, and anyway often the focus/other items are more important than resolution. A great picture is great and it just means you show it in smaller size!
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