Shooting wide open, AF on entry level DSLR

[unpopular]

I am finding that my older entry level dslr (a350) often misses focus, especially in moderate and low light or low contrasty situations when shooting wider than f/2.8, but using focus confirm is fairly accurate.

Being new to this AF stuff, I'm just curious if this is this typical of entry-level DSLRs, do mid-end DSLR's handle very shallow DOF better and are there any tricks to using AF with very shallow DOF?

 

[HughGuessWho]

It's not just about "entry level". Low light and low contrast makes it more difficult for any camera to auto focus. I dont think shallow DOF has nothing to do with it, except WHERE the focus is.

 

[KmH]

Auto focus is done with the lens open as wide as it can go. If the aperture is set to a smaller aperture for exposure purposes, the lens then stops down just before the shutter opens, but after AF was done when the lens was as wide open as it could be.

Kit zoom lenses that have a max aperture of f/5.6 at full zoom are usually at the limit of an entry-level auto focus systems capabilities.

No doubt, entry-level cameras have less capable auto focus modules than the prosumer and professional cameras do.

 

[dxqcanada]

My a100 and my a55 both have no problem focusing with my Maxxum 50mm f/1.7.

As KmH stated ... more to do with the AF system.

 

[HughGuessWho]

Of course, that goes without saying. My point was, low light and low contrast makes it more difficult for any camera at any price level. Am I wrong?

 

[dxqcanada]

You are correct ... low contrast does cause my a55 some problems ... and I do recall that my a100 did not like very low lighting.

 

[Kolia]

AF isn't as "fire and forget" as we'd hope.

I remember I had to pay attention to where exactly my a390 would focus. Often switching to spot focusing in difficult situation.

Now with the a65 phase AF, it has an easier time focusing. Less hunting and overall faster focus with the same lenses. But still not magical!

 

[KmH]

My point was, low light and low contrast makes it more difficult for any camera at any price level.

Yep.

The new Nikon D3200's low light AF detection limit is -1 EV, while the new D4's low light detection level is -2 EV, just 1 EV better.

Like Kolia mentions, auto focus is not the be all to end all.

 

[kassad]

Yep.

The new Nikon D3200's low light AF detection limit is -1 EV, while the new D4's low light detection level is -2 EV, just 1 EV better.

Like Kolia mentions, auto focus is not the be all to end all.

I have never understood what that measurement actually means. Can you Explain it or link me somewhere?

 

[DiskoJoe]

Yep.

The new Nikon D3200's low light AF detection limit is -1 EV, while the new D4's low light detection level is -2 EV, just 1 EV better.

Like Kolia mentions, auto focus is not the be all to end all.

I have never understood what that measurement actually means. Can you Explain it or link me somewhere?

Thats the exposure compensation.

 

[DiskoJoe]

Low light can make it a pain to af with lots of cameras. When the light is to low to get a good af I just use manual. Sounds like you manual down. You'll be fine.

 

[kassad]

Yep.

The new Nikon D3200's low light AF detection limit is -1 EV, while the new D4's low light detection level is -2 EV, just 1 EV better.

Like Kolia mentions, auto focus is not the be all to end all.

I have never understood what that measurement actually means. Can you Explain it or link me somewhere?

Thats the exposure compensation.

No there is a stat giving in camera spec measureing sensitivity of a camera's autofocus.

 

[rexbobcat]

Yep.

The new Nikon D3200's low light AF detection limit is -1 EV, while the new D4's low light detection level is -2 EV, just 1 EV better.

Like Kolia mentions, auto focus is not the be all to end all.

I have never understood what that measurement actually means. Can you Explain it or link me somewhere?

It means that the D4 will be able to autofocus accurately in light that is 1 EV (one stop) darker than the D3200.

 

[unpopular]

AF isn't as "fire and forget" as we'd hope. I remember I had to pay attention to where exactly my a390 would focus. Often switching to spot focusing in difficult situation. Now with the a65 phase AF, it has an easier time focusing. Less hunting and overall faster focus with the same lenses. But still not magical!

Thank you for your input, this is helpful as the a350 and a390 are almost the same camera. I have found that continuous AF seems to help, as if the AF software is averaging its input. I have also found that wide AF pattern helps accuracy, but I don't like using it since it chooses the front most object (I think). However, what it chooses is usually in focus, again, prob some kind of software feature not enabled in spot mode?