Sharp aperture for 50/1.8 and 28-105

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Hi

I have a 50mm/1.8 and 28-105 USM lenses. Could any one tell me at which aperture can I get a sharp picture using these lenses? I understand that for most of the lenses the best sharp picture can be obtained 2 to 3 stops closed from its wide open aperture. Is it true? If that is the case my 50/1.8 should give me sharp picture at f3.6-f4 and 28-105 at 8-11.

-- John (eosquestions@yahoo.com), April 22, 2002

Answers

Questions like this don't have a single answer. You'll have to determine for yourself. But unless you are trying the old home test-- using a tripod to photograph a section of classifieds from the newspaper with slide film and examining later under and 8x loupe--you probably won't see much practical difference among the apertures of your lens.

-- Preston Merchant (merchant@speakeasy.org), April 22, 2002.

Thanks Preston!

These lenses are new for me. I am not looking for a precise answer. Instead I want to hear from the experienced users of these lenses about a range of aperture in which I can get reasonably sharp pictures.

Thanks again

-- John (eosquestions@yahoo.com), April 22, 2002.


I own both lenses, and IMHO:

The 50mm produces very sharp images at about f2.8, and is brutally sharp at f4.

The 28-105 does nicely at f5.6, and better at f8.

That being said, I will shoot wide open if needed or stop down to f16 (at 28mm) for more DOF.

-- Kenneth Katz (socks@bestweb.net), April 22, 2002.


You can get reasonably sharp pictures with them at any aperture. Except perhaps the 50mm lens wide open. Of course, that's using my definition of reasonably sharp. There are other people that are convinced that these two lenses aren't capable of being reasonably sharp at any aperture.

Most consumer lenses and many professional lenses are at their sharpes 2-3 stops less than wide open. But some actually produce their sharpes images wide open. And I had one very poor 85mm f/1.8 (not a Canon) lens that was sharpest when stopped all the way down to f/22.

The Canon 50mm f/1.8 that I had was not very sharp wide open but was good at f/2.8 and very good at f/4. The 28-105 that I tested was decent wide open and improved substantially one stop down.

Of course these are all based on my definition of reasonably sharp & I'm not all that fussy about sharpness. I find that there are other factors that are much more important to image quality.

-- Jim Strutz (j.strutz@gci.net), April 22, 2002.


Typically 1-2 stops down from full aperture is the sharpest range for a lens.

There is also the old saying (which I personally feel is left over from the days when lenses weren't quite as good as now, and also is due to use of manual exposure systems) which is "F8 and be there".

-- Isaac Sibson (isibson@hotmail.com), April 23, 2002.



I don't have the 50/1.8, but I do have the 28-105, and did the traditional newspaper-on-the-wall lens test with it:

http://www.stevedunn.ca/photos/writings/eflenses.html

-- Steve Dunn (steved@ussinc.com), April 23, 2002.


I generally take shot between f8 and f16 to have the very sharp photos but beyond f22 the sharpness is decreased fue to defraction.

-- Neeraj Sinha (sinhaneeraj@hotmail.com), April 25, 2002.

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