Comparison of five lenses at 50mm

Started Aug 8, 2007 | Discussions thread
OP Prognathous Veteran Member • Posts: 9,217
Re: Updated results

Leon van Roosmalen wrote:

Looking at the pictures I can't see were the lens is focussed. The
areas your comparing are not in the center and the corner crop is on
a different distance.

Both the auto-focus and my own manual focusing resulted in the same focus spot - the end of the turn. To verify that I got focus right, I bracketed the focusing backwards using ultra-small turns, and the "best" result was at the end of the turn (where the lens is supposed to be set at infinity). Needless to say, it's impossible to bracket the focusing forward and past this point. I did the same with both copies of the lens.

Let's look at the facts:

1. Both the 1st generation 50mm and the RS version behaved the same, failing to produce sharp results at infinity even at f/4.0.

2. Three other lenses (all third party by the way) produced significantly sharper results at the same aperture.

What is your conclusion from these facts?

If you manual focus on infinity there are a lot of lenses that go
beyond infinity to compensate for temperature influence.

Again, bracketing the focus backwards did not help, in fact, the results I got this way were even worse.


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