Canon 300hs and *HUGE* f-stop/aperture numbers

Started Apr 27, 2011 | Discussions thread
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PaulRivers
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Canon 300hs and *HUGE* f-stop/aperture numbers
Apr 27, 2011

I thought I would make a new thread on the topic of the Canon 300hs apparently choosing ridiculously high f-stop numbers (like f14) when most Canons will not go above f8.0, causing very very soft images due to diffraction.

Original post -

Jinwons wrote:

I'm not that impressed by outdoor shots of 300HS so far. I get 2~3 somewhat blurry or soft shots out of 10 shots despite my best effort to hold it steady and messing around with AF, IS settings. Even the good sharp shots fall short of my ZS7 in details, sharpness a bit. Maybe I'm so used to seeing excellent outdoor shots of ZS7.
...

...then I realized that some of them got very low lens speeds like F/11~F/14. Looks like 300HS has its own mind on choosing lens, shutter speed. Sometimes it does high F/number, slow shutter and the other times it does low F/number, fast shutter speed combination even at the same shooting location. Although the total exposure is similar, bigger F/number+slow shutter speed causes soft images due to bigger diffraction spot and longer exposure. Unfortunately there is no way to control this behavior as 300HS doesn't have ASM modes.

I was going to the camera store (National Camera Exchange) to look at some other stuff, so I thought I would check this out while I was there. I grabbed a 300hs and tried to reproduce these absurdly high apertures.

I couldn't get it to do it at all, initially. It wouldn't go above f8.0. I went as far as setting the camera to spot focus, small focus area, and pointing it directly at a light - it (correctly) wouldn't do it. In this photo I used pointed the 300hs at an LED light I keep in my pocket and the camera maxed out at 1/2000 f8.0 iso100 and wouldn't bump up aperture up above that at all (actually I didn't get it in the picture, but just before this the text turned orange suggesting the camera couldn't go above this) -

It would not go above f8.0 no matter what I was pointing the camera at.

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Here's what's funny - when I wrote this:

PaulRivers wrote:

My point was the it's very weird for a Canon to do that...

Every now and then there's some weird bug where, like, you set the white balance to tungsten and it incidentally changes some other settings that means you get super high apertures or something. I was just suggesting doing "reset all" then trying it out and seeing if you got the same behavior.

It's not impossible that it's a faulty one, but in my opinion that kind of behavior is usually a firmware bug that affects all of the same model, not something that just went wrong with your unit.

I'm take a second to mention that the other poster wrote back -

Jinwons wrote:

Regarding the settings in 300HS that might cause this, I don't think your guess makes sensor much to explain it. I've only used smart auto for some and predominantly P mode with only focus, EV, icontrast changed. P mode still does automatic exposure with ISO, lens speed, exposure time no matter how we change other settings in there. Anyway I did reset and made a few changes on focus, ev and it's back the same setting basically. Doesn't make any differences. I believe this is firmware bug at least in my 300HS.

Obviously he felt my guess that changing some sort of setting doesn't even make much sense!

...though, it sounds like he did try it, and he uploaded photos, so I can't give him to much crap, and thus I'm also writing back.

I was finally able to reproduce the bizarrely high f-stop readings - by using the zoom. As soon as I started zooming, suddenly the camera was more than happy to jump up to absurdly high f-stops just as Jinwons had pointed out -

I'd like to hear back from other people who own a 300hs - do you find the same thing? Does the f-stop stay reasonable (f8.0 and below) when you don't zoom, but jumps up above that in bright light when you do zoom?

For reference, here's the original thread -
http://forums.dpreview.com/forums/readflat.asp?forum=1010&thread=38249204&page=2

And here's a thread with pics showing the effects of diffraction on the s95, a totally different camera, but since you can see the effects at f8.0 you can imagine how bad they get by f14 -

http://forums.dpreview.com/forums/readflat.asp?forum=1010&message=37655165&changemode=1

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