Fast lenses, and High ISO

Started Jul 18, 2014 | Discussions thread
Lee Jay Forum Pro • Posts: 51,879
Re: Fast lenses, and High ISO

Chikoo wrote:

Chikoo wrote:

Chikoo wrote:

ultimitsu wrote:

Chikoo wrote:

The only ability I see the fast lenses provide was actually a disadvantage that happened to become a feature, and that is shallow DoF, allowing for separation of subject from the background.

how is it a disadvantage when you can stop the lens down?

The purpose of designing larger apertures was to get more light in. The shallow DoF is a side effect or a by product of doing so.

You did not answer the question.

A F/1.4 lens can stop down to at the least F/16, often F/32. That ability is not different to that of an F/5.6 lens. So I am asking you again, how is it a disadvantage when you can stop the lens down?

At best, you could argue one cannot always make use of the large aperture advantage, specifically, when deeper DOF is required. But that is not what you said.

I apologize for nor answering your question directly. If you look at photo history, a picture contains everything you see through the viewfinder esp rangefinders. With larger apertures, that is not the case. The foreground and background blurs away. Stepping down takes care of that, but then it is no longer a fast lens.

You still did not answer the question. It has already been established that large aperture isnt always an advantage, but where stopping down is needed, large aperture lens can do so. So the question is still left unanswered:

How is it a disadvantage?

With more light, you lose background detail.

And you have large(r) lenses, heavier lenses, and in turn more expensive lenses.

Size and cost are indeed disadvantages, but there are generally no photographic disadvantages of having the ability to go faster. I've shot deep DOF shots at f/1.4 on full frame. In many cases, especially with larger subjects, the DOF change from f/1.4 to f/5.6 is not material, and thus the advantages of having a brighter lens are all about better image quality with no photographic disadvantages.

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Lee Jay

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