i found this on a different forum and thought I would share it... it is more for users of fast glass on cmos sensors... but interesting none the less... gives you pause before you replace that f/3.5 with a f/1.4 on most consumer cameras
Haha, you do me a fine compliment @icywarm ! It's always nice to be aware of things going on behind the scenes that you're not supposed to know about, such as the ISO-boosting low f-stop thing. It does seem to only affect the very top end lenses mind, like you say, and the "best" couple of f-stops, so I doubt there'll be enough weight behind it to fix it and introduce the notion of t-stops to the world of photography, or convince the manufacturers that boosting the ISO by 0.5 is really so bad, sadly.
Anecdotally, I can vouch for wider apertures (f/1.2) giving far better DOF control. I can also vouch for the image sharpness being better, not at wide open, but at "stopped down to the same as" the cheaper glass. I know, from use, that my 1.2 glass has shallower DOF wide open than my 1.4 glass , but also I'm looking near the centre of the frame (relatively speaking) where the light is hitting the sensor sites more directly (as per the link).
Technically, the information is very interesting, and it may serve to help re-evaluate lens performance with certain sensors, but it doesn't seem to be taking into account that most photographers don't shoot wide open. What I mean is, I didn't buy f/1.2 glass so I could shoot all the time at f/1.2 - I stop down slightly to achieve maximum sharpness, while achieving the DOF I would get from cheaper glass wide open which doesn't give me that sharpness. When I bought my f/1.4 glass, I thought it was brilliantly sharp. But the f/1.2 glass blew me away all over again. And both are better than my f/2.8 zooms.
Thanks for the link! I'll be interested to see the results of their other testing!
This is useful to make me realise there is sooooo much to learn and my capacity for retention of such information is somewhat limited. My old SLR used to have a sticky label on it to remind me what to do for all the key situations - I might have to resort to that for my digi SLR, but somehow think the information now required has expanded enormously and wouldn't fit the same label!!
@jinximages that's funny you found this too... you are the other 365 I had in mind when I posted this.... I concure about the stoping down... also the coatings are much better I find... and little details like being able to manual tweak focus well still in autofocus...
@icywarm Classic! :D Yeah - it's not just about the aperture is it. Speaking of lens coatings - that's why I'd really like the Zeiss 50mm for my Canon - it might be $10k or more, but they've reduced CA and such by the quality of the glass, instead of coatings. I really wish Canon and Nikkor would explore that more, instead of all these coatings they use - it might reduce their need for the hidden ISO increase.
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Anecdotally, I can vouch for wider apertures (f/1.2) giving far better DOF control. I can also vouch for the image sharpness being better, not at wide open, but at "stopped down to the same as" the cheaper glass. I know, from use, that my 1.2 glass has shallower DOF wide open than my 1.4 glass , but also I'm looking near the centre of the frame (relatively speaking) where the light is hitting the sensor sites more directly (as per the link).
Technically, the information is very interesting, and it may serve to help re-evaluate lens performance with certain sensors, but it doesn't seem to be taking into account that most photographers don't shoot wide open. What I mean is, I didn't buy f/1.2 glass so I could shoot all the time at f/1.2 - I stop down slightly to achieve maximum sharpness, while achieving the DOF I would get from cheaper glass wide open which doesn't give me that sharpness. When I bought my f/1.4 glass, I thought it was brilliantly sharp. But the f/1.2 glass blew me away all over again. And both are better than my f/2.8 zooms.
Thanks for the link! I'll be interested to see the results of their other testing!