Topics

1

Lenses / AF error tolerance

« on: June 16, 2011, 02:53:54 AM »

After posting here, I got the 400mm 5.6 lens, but it is front focusing. The front focus is about 2cm. The total DOF is about 6cm, which makes it only 3cm from the center to the front/behind, when lens positioned about 7m @ 5.6. Measurements are rough and not very accurate.
 
I noticed that the longer the subject distance, the bigger the error.

Shooting the moon, the phase detection focus showed softer results consistently compared to contrast detect focus when viewed 100% crop. I used tripod, cable release and shot all photos in live view (including the phase detection focus).

I don't know if this is within acceptable tolerance, but even if it is, I don't like the results. Since I don't have micro adjustment, I don't know if the error can be fixed with it for different subject distance.  Also, the focus ring wobbles a bit too much, enough to make 'loud' wobbling noises, and there was some dirt on the lens body, which I removed without any problem.

Got this from Amazon uk, do you think I should replace it ?

2

Lenses / Canon EF 400mm f/5.6 L USM

« on: May 28, 2011, 06:57:13 PM »

After some math, I concluded that 400mm @ 5.6 should give me a good background blur (different from depth of field) when used on a FF camera for a framing about 2m - 2.3m height in landscape orientation. In fact this combination blurs the background slightly more than an APS-C 300mm @ 2.8 combination, after adjusting the subject distance to get the same framing. I will get even more background blurring in portrait orientation for the same height, and for tight crops, so if I am not missing something, I am interested in getting a copy of this to be used in sports on a future 5DIII in daylight.

I considered the bigger lenses alternatives too, but apart from the high price problem, I am afraid of weight, especially since I will also have a 70-200 on another body, and I prefer to move around comfortably and fast rather then standing still or move awkwardly due too a big lens + monopod.

The weak points of this lens are

(1) no IS, which I don't need in sports (I switch it off on my 70-200 2.8 IS II)

(2) No weather sealing, this is good to have but I will fix this problem with a hydrophobia (might be too big for this small lens) or an equivalent product.

(3) 3.5m MFD, which is not a problem for my use.

The strong points are

(1) very good image quality, (resolution, CA, vignetting, distortion, flare, bokeh)

(2) very fast AF which is extremely important for me.

(3) weight of 1.25kg & cheap price.


Am I missing something ? Do you have any other alternatives with my priorities in mind ?