Discussion: Hi ISO's vs 'Fast lenses'

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James Greed

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Does the availability of hi ISO's on modern digital SLR's reduce, or even eliminate the need for 'fast' lenses? - Discuss.

Off you go...
 
Fast apertures are all about DOF for me more than improving shutter speed. So, no, I think there is still a need for fast lenses.
 
ryanyboy said:
Fast apertures are all about DOF for me more than improving shutter speed. So, no, I think there is still a need for fast lenses.
Click to expand...

I agree, and another advantage is fast zooms tend to be constant app. as well - no changing exposure as you zoom
 
Quite obvious the answer to this isn't it?

Besides reducing exposure times, what other effects might you expect to see with a wide aperture and why might these be desirable in their own right besides adding more light to your exposure?

Answer that and you'll have the answer to your original question :D
 
Fast lenses focus quicker and more accurately in poor light.
 
Yes, it reduces it. No, it doesn't eliminate it.

But if you don't actually want shallow depth of field, which a lot of the time you don't, then high ISO coupled with IS works very well a lot of the time.

This seems to be the way things are moving. Zooms with modest f/numbers, better high ISO, IS as standard etc. All this is getting cheaper (relatively) but nice fast primes are as costly as ever.
 
No because why would you be happy with one of them?

why not push the envelope and be able to work in new ways in less light and get pictures where you couldn't before?
 
As well as DOF and low light focus ability, the faster lenses are usually significantly sharper...
 
The accuracy of, and to some extent the ability to use, a phase detection based AF systems revolves around the aperture diameter (and format size). Contrast detection based AF would have to come to the fore but with improvements to cater for the reduction in light.

Bob
 
I had a choice when buying my long lens, I chose the 200-400mm over the 400mm prime to give me flexibility in what i do, knowing i could make up the difference between F4 and F2.8 with the ISO performance of the D3 so yes in my opinion it has started to open up a new world of opportunity's I never had before.

Over a hundred feet the 2.8 gives around 4ft of DOF and at F4 it is 4ft so not as much as one may think. I also need more DOF not less, it is a constant battle to match both shutter and DOF and with the ISO ability I certainly have the choice.
 
Certainly reduces it for people who can't afford fast-aperture lenses.

Look at it this way; you have one of the new breed of consumer DSLRs that are good up to 12,800 for example - now you can use your standard f/4.5 - 5.6 kit lens in all conditions without camera shake or flash. For budding togs on a budget I think that's a no-brainer.

However, for ultimate creativity there is no substitute for the maximum DoF you can get your hands on and that's why I'll try to plump for a fast lens first and then look at how high I can push the ISO later.
 
Just because a lens is fast doesn't mean you have to always use it wide open. A nice bright viewfinder and shallow DOF for focussing (I can actually Manual Focus with my 1Ds and 50mm f/1.4 accurately, and damn that is a good feeling!) are nice to have too.

High ISO is good though as it isn't always appropriate to have a paper thin DOF! :P
 
If you're in a situation where you don't want shallow DoF then you can't open up your lens, however fast it may be... so to get the exposure you need high ISO or slower shutter speeds and it's only ISO that's going to save you from movement in your shots.

It gets you away from sacrificing DoF for exposure which is only going to widen the scope your of photography; no more choice between fast but shallow or slow but deep, now you can have fast speeds and depth of field too!

Of course there's no replacement for a wide-aperture on a lens when you want that DoF but I think we're starting to see a change in attitudes - away from the idea of 'fast glass' towards a 'fast sensor' ie, usable high ISO.




Edit: just realised the middle paragraph might sound a little dodgy for some people!
 
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