Hi Don, my comment about Andy Rouse, whilst true, was put in tongue in cheek for a bit of fun. His criteria is obviously wildlife photography so presumably follow focus among others. Robs comments on focusing on the mug agree with my comments about working around problems by using the single central focusing point and finding an edge for greater contrast. Given two lenses of the same 'speed' and focal length one sometimes seems to focus better than the other which I have always put down to one lens having better contrast than the other. Any thoughts on that?

Things have moved on a ways since then, Nikon focussing is a different beast now - eat your heart out Andy Rouse!

nirofo.

Mike,
I do not have two similar A/F lenses to check out the lens resolution bit but I guess when you reach the boundarys everything counts. :)
So I have just looked at Photozone reviews of the Sigma and Tamron to look at the MTF charts and the Tamron has it by a nose.
Now going back through the thread to crazee horse second post and he says " we both put the cameras on auto and then program and focused on the same thing. ". In this case that may also have relavence. What auto/program mode was used ? From my experience of the 350D then if it is on basic program ALL A/F points are live just the same as the D50. In this case his friend may have set Vari program on the D50 and that would allow him to set a single central A/F point.

From a specs point of view ( DPR ) the 350D A/F range is EV -0.5 to + 18, D50 range EV -1.0 to + 19 so the D50 has it by 0.5 EV
Lenses from photozone MTF at 300mm, Sigma on the 350D MTF centre 1676 edge 955, Tamron on the D50 centre 1849 edge 1489. Advantage the Tamron on the D50

The unknown is then selected focal length. As these are both variable aperture lenses if the guy with the D50 was at less than 300mm and crazee horse at 300mm then it would be advantage D50. Could have been f5.6 on the 350D and say f5.25 on the D50.

Hardly scientific, but add all these factors up and the result would be as described.

Don

Some info from a Canon write up on AF

"The camera's AF sensors require some details in the image to determine the phase difference. It's harder for the camera to find focus when the light is dim or there is little subject detail. Contrary to recent remarks on another topic, the camera CAN distinguish contrast between equally bright hues of red and green just as the eye can--the sensors are color corrected. Although the sensors can distinguish some quite subtle detail differences, they don't see quite a sharply as the eye. If the lens starts from a very out of focus condition, it can miss very fine detail that the eye sees clearly, such as the mesh of a speaker grill from across the room. In this case, it can be helped if the photographer manually moves close to "focus" and allows the camera to find the actual focus."

Well Andy Rouse buys and pays for his own gear (much to his annoyance- he feels Canon should do a deal with him) so if he feels Nikon are that much better and would get him shots he would otherwise miss I guess he would jump brands. Then of course it would all change around again at some point!
Don , interesting answer to my question. I don't pretend to understand MTF charts etc but it certainly shows there is a lot more to it than simply pointing two cameras at the same subject to see which is better! My bother-in-law
went out the other morning with his 400D and at 6.30am in woodland in very poor light got his photos of deer with no problems.

Forget low light, try focusing on fog, or a clear blue sky, my D400 does, my mates Nikon............um.............dosen't!

:D :D

Better is what you decided to buy for whatever reason. Just enjoy using it.

While taking pics for a thread today I thought of watches as an analogy. Some people have a Rolex, I have a Seiko. Mine might not maintain time to a nano second but it does for me.

For Rolex owners then I can understand why you have one. I bought a F2's because I appreciated the mechanical precision but I took no better pics with them than I did the relatively lowly FM's that I traded in to get them. Just enjoyed using them more. :rolleyes:

Don

Trying to understand the motivation behind that one. :confused: :confused:

I think I'll pass unless checking sensor for dustbunnies. :)

Don

Well I guess this is where we first came in, playing with some one elses camera for fun and curiosity. As you say Don I just enjoy taking photos and also just playing with cameras (sad I know). I have a niece who is a psychologist but I daren't tell her! :D

Best statement in this thread so far.

I bet you the Seiko will keep better time than the Rolex. ;)