Focus calibration tests

[koffiejunkie]

I mentioned in another thread that both my Sigma 30mm f/1.4 and Canon 50mm f/1.8 front focus consistently on the new body. Just some background: the comments was based on pictures taken at a party at my place. I had the 7D and these two lenses out, two more peole who are accomplished photographers, and about three more who have no idea what they're doing, all took pictures with it during the course of the evening. So I consider the gear to be at fault, given that about six people all got the same results.

So I did some focus tests with the focus test chart tonight. Both lenses focussed correctly, consistently. I also ran the tests at 30mm and 50mm with the 24-105L for comparison. Not surprisingly, it focussed accurately and fast all the time. So I can only guess that something about the quality of light threw the focus off?

As an aside, it's interesting to see the sharpness of these thre lenses. At their respective wide open settings, the 24-105L makes a mockery of the other two. If I stop the two primes down to f/4, they're about comparable to the 24-150L but only just, and it's worth keeping the mind the 24-105L is still wide open! One sweet lens

 

[hilton]

Is this Canon EF 24 - 105 mm f 4.0 L IS USM lens?

 

[koffiejunkie]

Yes

 

[SubliminalThought]

One sweet lens

+1. Its on my 50D 90% of the time.

 

[bwana]

You're surprised a f/4 is sharper than a wide open f/1.4?

 

[koffiejunkie]

You're surprised a f/4 is sharper than a wide open f/1.4?

Given that f/4 is wide open on the lens in question, and given that lens in question is considered soft wide open, a little, yes. I'm only looking at the center - don't expect anything else to be any good at f/1.4. Both the 30mm f/1.4 and 50mm f/1.8 are shown to be sharper in the center wide open than the 24-105L in the photozone reviews. But of course, real life is a different story.

 

[bwana]

Given that f/4 is wide open on the lens in question, and given that lens in question is considered soft wide open, a little, yes. I'm only looking at the center - don't expect anything else to be any good at f/1.4. Both the 30mm f/1.4 and 50mm f/1.8 are shown to be sharper in the center wide open than the 24-105L in the photozone reviews. But of course, real life is a different story.

Of course - your first post highlighted this (in the form of user error).

Speaking from experience the Canon 50mm f/1.4 is incredibly difficult to use wide open, with a razor thin DOF but then again at least you can do it. Stopped down to f/2 it's much sharper.

 

[koffiejunkie]

Speaking from experience the Canon 50mm f/1.4 is incredibly difficult to use wide open, with a razor thin DOF but then again at least you can do it. Stopped down to f/2 it's much sharper.

Agreed, f/1.4 isn't for the faint hearted. For what it's worth, in the event described in my first post, I had the camera in M, with 1/80 and f/2.8 and Auto ISO. f/2.8 on a 30mm with, say 1m focus distance (most shots were at about this distance or longer) means 11cm of DOF. That's pretty tough to miss.