LowLight Cam - f2 vs. high ISO

[goletitout]

Hello everyone !

I currently own a Powershot SD500, but I´d like to have a a cam which is more capable in low light situations. All those threads dealing with the Fuji F10/Olympus 800 are very interesting, but there´s one thing I´m not sure of : what is better : a fast lens or higher ISO capabilities ?
I know I´m about to compare nearly uncomparable cams, but I can see no way out : should I rather buy a Powershot G6 or a Fuji F10 ?? I mean, especially concerning their low light capabilities an also in general. Is it better to have ISO1600 with acceptable noise or a F2 lens ?
Camera size isn´t that important to me.


If you read the G6 test on dpreview.com, it is also mentioned that the G6 is 2/3 of a stop more sensitive than indicated. ISO100 corresponds to ISO160, ISO200 to ISO320, ISO400 to ISO640. That means the G6 is capable of taking ISO640 shots which also don´t look worse than most other cam´s ISO 400 shots. This, in combination with the fast lens (is it true that an f2 lens makes it possible to take the same photo with a shutter speed twice as fast as with F2.8 ?) should make the G6 a very very capable low light cam (more capable than the Fuji F10 ? I don´t know).
Then again, I read reviews discussing major low light focusing problems of the G6...I don´t really know what to think. I hope to find some experts here who know better.


Thanks in advance,
Tilo

[jamison55]

For purely low light purposes the Fuji F10 is more capable. Here are my reasons:

Forgive me if I am insulting anyone's intelligence, but remember that every stop is a doubling or halving of the light gathering abilities of the camera. A shot that you could take with a camera at 1/60 f2 would require 1/30 f2.8, since f2.8 is one stop slower than f2. ISO settings work the same way, each bump to the ISO increases the light gathering abilities of the camera by one stop. So using the example above, if the 1/60 f2 camera was set to ISO 100, you could get the same exposure with the f2.8 camera at 1/60 if you up the ISO to 200 (i.e. 1/60 f2 ISO100 = 1/60 f2.8 ISO200)

At the wide end the Fuji is 1 stop slower than the G6 (f2 vs f2.8), but you can get good images at ISO800, and usable ones at ISO1600. Looks to me that the G6 isn't usable above ISO200, and even that's pushing it. So if we work out the math, the Fuji is 2 stops faster than the G6 (since the G6 tops out at ISO200, for all practical purposes, which is equivalent to ISO400 on the Fuji).

That means that the Fuji is handholdable in 1/4 the light of the Canon!

That's strictly on low light, however. The Canon has many more manual features, that cool swiveling LCD, and external flash support (a 420EX gives you miles more light than 2 stops...)

[goletitout]

I don´t think you can compare ISO200 on a G6 with ISO1600 on an F10. When I look at the sample pics at dpreview.com, there´s even significantly less detail in the ISO 1600 shot of the F10 in comparison with the ISO400 shot of the G6. Ok, the G6 has a lot more noise, but the F10 photos at ISO1600 lose a lot of detail due to aggressive noise reduction. I rather think the ISO800 shot of the F10 and the ISO400 shot of the G6 look comparable. Or at least ISO800 on F10 and ISO200 on G6 might be comparable, even though there are no ISO200 sample shots on dpreview. Then the F10 would be 1 stop faster( because of the difference in aperture)...and after that, you have to reconsider that ISO200 on the G6 is ISO320 in reality(Canon has labeled the ISOs too low, see dpreview.com)...then the F10 would be just 1/3 stop faster, am I right ? Oh I hate these calculations...

[ZCarroll]

I've really been wondering this one myself... and add to that is a larger lens f/2.8 "faster" than a smaller cam f/2.8? I thought aperture size was aperture size but I'm finding it doesn't really seem to be so? At least the only reason I can figure why these ultra compacts with the same f stop perform not as well in low light? It makes digicam shopping all the more difficult especially since the reviews don't seem to address this issue for what I'm looking for..

???

[jamison55]

I've really been wondering this one myself... and add to that is a larger lens f/2.8 "faster" than a smaller cam f/2.8? I thought aperture size was aperture size but I'm finding it doesn't really seem to be so?

Aperture is aperture DSLR or compact. A compact digicam @ f2.8/ISO100 should require the same shutter speed as a DSLR @ f2.8/100. However, with digital cameras, there seems to be some discrepancy between what ISO 100 means on different makes/models.

DSLR's are typically said to be better in low light because of their superior high ISO performance. I routinely shoot at 1600 on my 20D and 800 on my 10D with very acceptable results. That means I can handhold my DSLR's in light that is far lower than the average compact. DSLR's also give the ability to choose a wider lens, giving me more low light options. If I own a Panasonic fz20 I am stuck at f2.8, but with my 20D I could purchase an 85 f1.2, which is 2.5 stops faster (or, if I could find/afford one, a 50 f1.0 - 3 whole stops faster).