do you really need faster than f/2.8

Started Sep 25, 2012 | Discussions thread
ZOIP Junior Member • Posts: 46
Re: do you really need faster than f/2.8

So the question is "do you really need faster than f2.8". I guess the original poster was thinking in terms of the DXO findings rather than the practical application of fast lenses.

My opinion based on years of pro work and lots of personal stuff as well is that fast aperture lenses, those beyond say f1.8 are basically a waste except from some very very limited situations.

Allow me to explain:

These days the need for shooting at the extremes of light gathering power is pretty much a non issue, most cameras can shoot at far higher ISOs than we could have a few years back.

I feel much of the excitement over fast glass is due to current shallow DOF fashion, bragging rights and most importantly people looking at web images as the final product.

Web images are the lowest common denominator in imaging work and all things being equal due to size and the real lack of resolving power benefit a bit from shallower DOF than is required for actual prints.

The truth is most of the images photographers get excited over with regards to DOF when looking at web stuff are hopelessly inadequate when it comes to creating the golden standard if shot wide open, i.e. a high quality print. In other words they actually lack critical sharpness anywhere. But there is more...

More often than not the actual plane of sharpness is somewhat misplaced due to the extremely shallow DOF and the inevitable focus errors that most cameras have unless you are careful and work in magnified live view. Really sharp shots are inevitably a lottery.

Beyond that most but not all fast glass exhibits some pretty serious issues at the wide open setting, such as significant spherical aberration, fore/aft CA, lack of real resolution even on centre.

Taken further a great proportion of fast lenses have high levels of focus shift when stopped down to more normal apertures making critical focus somewhat of a lottery.

And for all this you pay crazy money and have the burden of carrying around a significantly heavier lens which may cause balance issues on your camera.

A really good f1.8-f2 lens is all most users ever need, even those wanting shallow DOF, shoot a 50mm f2 lens wide open and make an 8 by 10 print, I would hazard a guess it would be plenty shallow enough for any sane requirement.

In some ways the appearance of shallow DOF is proportional to the actual in plane sharpness, in other words if you can get the intended focus plane really sharp, the out of focus areas look less sharp. An example: For those NEX owners lucky enough to have a 55mm f2.8 micro nikkor, try shooting wide open at 2.8, you will be surprised just how shallow the DOF actually looks because this lens is so critically sharp wide open on the actual plane of focus.

Often Bokeh is held up as a fast glass justification, but here again many lenses exhibit far better Bokeh when stopped down a notch or two.

In the end I feel there is an awful lot of cash spent on fast glass for no real beneift.....unless of course you do actually intend to shoot web images wide open, or you are wanting to play for a particular artistic look. But in the end fast glass sure makes lots of cash for lens makers.

Me I just want really sharp f1.8-2.8 lens that are not compromised.

Just my 2 cents worth.

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Trying to make the complex simple

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