Archive for February, 2010

Niffty Fiffty, buyer beware !

Sunday, February 28th, 2010

I have wanted a 50mm f1.? lens for a while and struggling with my options.

Canon 1.8
-ve : Only 1.8, feels like a kinder egg toy
+ve : Very very cheap.
Canon 1.4
-ve : Build quality hit and miss, not an ‘L’ lens, only 5 blades.
+ve : Canon brand
Canon 1.2
-ve: Very expensive and will it be worth it.
+ve : ‘L’ Series
Sigma 1.4
-ve : Not canon, Build quality hit and miss.
+ve : 1.4, 9 round blades, large front lens so will take my P filters
After much pondering I finally decided to go for the Sigma but to test it carefully, and boy glad I did !

The problem all fast lenses have is that at the max aperture the DOF is so small that the auto focus can be off, either front or back focusing. This isn’t normally a problem if your shooting at f6 as the DOF is quite deep but at f1.4 close up on a 50mm depth of field is only about 20mm so its critical.

To test the best way is to photograph a sheet of text at 45 degree angle so the text runs from in front of focus, at focus , to behind point of focus.
Set the center AF focus point only (but NOT manual focus) and shoot away.

This is more (or less) what you should get, but bear in mind these are hand held at high ISO.
The focus point is set on the AF-S 50mm 1.4.

More or less okay :-

Sadly this is the results I got :-

As you can see this is quite a way behind the autofocus point.

Needless to say I didn’t buy this lens, but it is very subject to manufacturing so every lens (sigma, canon, even L series) can suffer so YOU MUST TRY BEFORE YOU BUY. Next time you buy a fast lens make sure you give it a try.
In the mean time I’ll keep up my hunt for a niffty fifty.

p.s. You can also get very retentiveve with tripods, flashes, printed test cards etc. but I think lens testing and pixel counting is for people who can’t take photos so have to justify there “photographic existence with statistics.

Cheers,
Richard B.

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