Why would ppl pay so much to save iso?


maisatomai

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Oct 26, 2006
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#1
400mm f5.6 cost 1000+
400mm f2.8 cost 10000+

If to get correct exposure for first lens aperture 5.6 shutter 30 iso 1600, wun the 2nd lens have the same aperture same shutter at iso 800? Sorry if I am misinformed
 

Hanmin147

New Member
Aug 20, 2011
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#3
maisatomai said:
400mm f5.6 cost 1000+
400mm f2.8 cost 10000+

If to get correct exposure for first lens aperture 5.6 shutter 30 iso 1600, wun the 2nd lens have the same aperture same shutter at iso 800? Sorry if I am misinformed
It's not only the iso that the aperture affects. With bigger aperture there is shallower depth of field or in layman terms it means that the background would be much blurrier and the bokeh would be much better. Hope this helps, google the terms if you do not understand. :)
 

maisatomai

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Oct 26, 2006
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#4
But if I am taking bird in flight which requires a lot of crop then will make the difference?
 

JasonB

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Jun 2, 2009
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#5
Two stops of light is 2 small numbers to the uninitiated but a hell lot of difference in photographic terms.

Focusing at f/2.8 is way faster than f/5.6 which matters to a sports shooter or maybe birders.

Plus you often put tele converters to it which cause a few stops of light lost. If the f5.6 becomes f/11 focusing suffer even more.

If you put a 2X tele converter, it means 1/800 speed at least, which again taxes on your ISO resulting in weaker files.

And, glass quality of larger apertures lens often better and also means you can afford to stop down a bit and get better sharpness and tones.
 

avsquare

Senior Member
Jan 26, 2012
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#6
400mm f5.6 cost 1000+
400mm f2.8 cost 10000+

If to get correct exposure for first lens aperture 5.6 shutter 30 iso 1600, wun the 2nd lens have the same aperture same shutter at iso 800? Sorry if I am misinformed
There is a lot of reasons and applications for a person to get that f2.8 version.

Firstly, f2.8 is 2 stops wider than f5.6, which means it will allow 4x more light into the sensor. This means a lot to the photographer.

DOF and bokeh aside, the most obvious application for f2.8 is for action/sports photography, or when you need to handle low lighting situations.

Theoretically, you are right on the ISO adjustment part. But whether it is applicable to the situation or whether the picture taken is usable is another matter :)

For example, in indoor sports photography, the photographer may need a shutter speed of 1/500s to stop action. To take a good picture with 1/500 indoors without good lighting is not going to be easy. Now let's compare both lens:

Assuming @ 1/500s, f2.8, ISO1600 is required to get a correct exposure
- Then @ 1/500s, f5.6, you will need to use ISO 6400 to get the same exposure.

Image quality and the amount of noise for ISO1600 VS ISO6400 can be quite a big difference. Worse, if ISO3200 is required on f/2.8 to give you the exposure you want, that would mean a ISO12800 on the f/5.6 for the same exposure. A picture on ISO12800.. the result may be garbage to a person who wants serious IQ. :p

A wider aperture generally allows better and faster AF. Another important factor when you need to snap quickly. Also, if you mount the f/2.8 with either a 1.4x or 2x extender, it is still fine and AF is still possible. But for the f5.6, the 1.4x extender would make it a f8 lens and AF would fail, unless you are using the EOS 1D series (1D series allow AF up to f8).

Not to forget, the usual rule of thumb for hand-holdability without IS to prevent handshake is 1/focal length. 400mm would mean 1/400 shutter speed. As f2.8 is 4x wider than f5.6, it allows you to use 4x faster shutter speeds without sacrificing ISO speed, which allows you to manage handshake better.

The list goes on - and that's why for a similar lens, you will find f2.8 commands a much higher premium than it's narrower brothers. :)
 

cks2k2

New Member
Feb 12, 2009
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#7
Not to forget, the usual rule of thumb for hand-holdability without IS to prevent handshake is 1/focal length. 400mm would mean 1/400 shutter speed. As f2.8 is 4x wider than f5.6, it allows you to use 4x faster shutter speeds without sacrificing ISO speed, which allows you to manage handshake better.
TBH no sane person is going to handhold the large aperture super-teles.
 

avsquare

Senior Member
Jan 26, 2012
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#8
TBH no sane person is going to handhold the large aperture super-teles.
no doubts on that, I guess that's a slight off-track to talk about allowing faster shutter speeds given the same ISO speed. :p
 

avsquare

Senior Member
Jan 26, 2012
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#10
If there's a will, there must be a way.... it just takes some training :D

If only if my arm is that muscular.. I may give it a try.

AND if my wallet is that fat to buy that monster. :bsmilie:
 

edutilos-

Senior Member
Dec 28, 2010
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#13
400mm f5.6 cost 1000+
400mm f2.8 cost 10000+

If to get correct exposure for first lens aperture 5.6 shutter 30 iso 1600, wun the 2nd lens have the same aperture same shutter at iso 800? Sorry if I am misinformed
2 stops means a lot sometimes. If say, you're a birder, and your absolute acceptable highest ISO (for IQ) is ISO 3200, it will save you from having to push the ISO to 12800.
 

Dec 12, 2009
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#15
Summary of what ppl mentioned f2.8 vs f5.6.

Same iso: 4x faster shutter speed for f2.8

Shallower dof for f2.8

Same shutter: Allows 2 stops less ISO -> cleaner images.

F2.8 allows adding teleconvetor 1.4x for good and cheap way to extend range (I would not recommend 2x converter)

Cost?

You compare the size and amount of glass needed to make f2.8 vs f5.6. Not to forget cost to make the bigger barrel, more 'powerful' motor (to drive more glass fast) etc.

Similarly you can go compare say 200 f1.8 L vs 200 f2.8 prime and see the price difference when both units were available.
 

Dec 12, 2009
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#17
But if I am taking bird in flight which requires a lot of crop then will make the difference?

I think this depends on the resolution of your camera sensor and also IQ of f2.8 vs f5.6.
 

Blur Shadow

Senior Member
Sep 17, 2005
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#19
Think the use of a larger aperture has been mentioned by many, so I won't repeat.

There's also the image quality issue. Although not always true, the larger aperture lens typically has better image quality due to better design and / or use of materials, thereby the higher cost.

Disclaimer: I hope fellow CSers do not misunderstand or misquote me. I'm just trying to explain another possible reason why a larger aperture lens may be more expensive - that it may be, inherently, more complex in every possible way, such as design, materials, construction, such that it is to, ideally, produce better image quality.

There are, and will always exist, exceptions to this notion.
 

Cowseye

Senior Member
Mar 7, 2010
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#20
Didn't anyone realize the ISO is drop to 400 instead of 800? It's 2 stops from 1600. 1600 -> 800 -> 400

That alone is a great leap.
 

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