Go Back   Steve's Digicams Forums > Digicam Help > What Camera Should I Buy?

Reply
 
Thread Tools Search this Thread
Old Feb 9, 2010, 12:25 PM   #31
Member
 
Join Date: Dec 2009
Posts: 37
Default

The other thing I noticed when I was playing with the D5000 with the zoom lens, was that when I turned off the IS, it seemed to focus a lot faster, while with the IS on, it seemed really slow. Is that something that happens with all lenses with IS on?
JM667 is offline   Reply With Quote
Old Feb 9, 2010, 12:57 PM   #32
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

I doubt it (if anything, AF should be *better* with stabilization, since the AF sensors see a stabilized view with it turned on)

Chances are, the "seemed" part of your impressions was being caused by something else. That's often the case with user impressions of Autofocus, especially when using supersonic focus motors, which are very quiet. For example, I personally consider the Nikon D300 to have a somewhat sluggish AF system using some lenses when changing focus distances significantly (at least with the original 1.0 firmware), as compared to my Sony A700 (and more than one reviewer noted sluggish AF with the D300 when all 51 focus points, even though some reviewers praised it's AF system as being best in class).

IOW, the D300 *seems* very fast unless you're paying close attention to the viewfinder (how long it's taking to bring your subject into sharp focus in the viewfinder) and looking at images it took in greater detail (i.e., the percentage of in focus versus out of focus photos when you're changing focus distances significantly and taking shots, especially using continuous drive and focus modes). Yet, the D300 has an outstanding focus system for tracking *after* it finally achieves accurate focus on your subject (which is not necessarily when it starts taking photos, even if it's set so that it's not supposed to shoot without a good lock).

IOW, just because one camera "seems" faster than another, doesn't mean it really is faster when focus accuracy it taken into consideration, especially when significant differences in subject distance are involved. Tracking also comes into the equation (how well the camera can predict where the subject is going to be for the next shot shooting in continuous drive modes, which is important for taking bursts when tracking action). Determining the camera with the "best" AF is not easy, as you've got a lot of variables involved (including conditions and light levels, subject type, whether or not it's moving, lens used and more). But, IMO, the D5000 does just fine when compared to other cameras in it's price range (and I have spent some time using one). Overall, Nikon's AF systems are superb, especially when you take "real world" conditions into consideration (even if lock time may test slightly slower than some cameras), with momentary obstacles entering the frame in front of your intended subject (where Nikon's AF systems handle that kind of thing nicely).
JimC is offline   Reply With Quote
Old Mar 29, 2010, 1:40 AM   #33
Member
 
Join Date: Dec 2009
Posts: 37
Default

Sorry to bring this up again, but I still haven't bought a camera and still pick them up everytime I go to a store that has them. I guess that doesnt hurt since I am still in no big hurry. But I did mention something in this post a long time ago about autofocusing seeming slow on the telephoto lens, and here is what happened today. At the store, they had the T1i with the 18-55 lens and when I zoomed in and out with that and took a shot, it was pretty instant. They had the D5000 there that had the 75-200 or whatever the kit lens is for that, and when I took a shot at the 75, then zoomed all the way out to the end of the range, it appeared blurry in the viewfinder, then when I pushed the shutter to take the shot, it took what maybe seemed like a second to focus and take the shot. So is that something common with any type of camera with a kit lens like this because the lens is slower than an expensive one, or is it specific to this Nikon because of no auto focus motor in the body? Would this same thing happen on the Canon?
JM667 is offline   Reply With Quote
Old Mar 29, 2010, 1:53 AM   #34
Senior Member
 
shoturtle's Avatar
 
Join Date: Dec 2009
Location: Frankfurt AM
Posts: 11,348
Default

The canon kit lens is slower then their next tier lens, and I have both for my T1i, but I once I push the shutter halfway it focus. I see the af lock and press fully and it take the photo with out any issues, with the IS on. But if you focus close, and then zoom out it will take the camera a moment to refocus for the new range. The 2 kit lens on the nikon would be the 18-55 an 55-200mm or the 70-300mm. The canon does have a faster AF system, actually the best in the enter level segment. But I did not think that the nikon AF was that slow with the kit lens when it refocused. But it has been almost a year since I played around with the d5000.
__________________
Super Frequent Flyer, no joke. Ex Patriot and loving it.
Canon Eos 60D, T1i/500D, Eos1, Eos 630, Olympus EPL-1, and a part time Pentax K-X shooter.
shoturtle is offline   Reply With Quote
Old Mar 29, 2010, 1:56 AM   #35
Senior Member
 
shoturtle's Avatar
 
Join Date: Dec 2009
Location: Frankfurt AM
Posts: 11,348
Default

Also if you were in single shot mode it will go through the AF cycle every time you release the shutter button. To have it focusing all the time you need to put it into continuous focus. That way as long as you keep the shutter half press it keeps focusing on the target.
__________________
Super Frequent Flyer, no joke. Ex Patriot and loving it.
Canon Eos 60D, T1i/500D, Eos1, Eos 630, Olympus EPL-1, and a part time Pentax K-X shooter.
shoturtle is offline   Reply With Quote
Old Mar 29, 2010, 2:31 AM   #36
Member
 
Join Date: Dec 2009
Posts: 37
Default

Ok that makes sense that it would take time to refocus after you zoom it all the way in. I'm not sure what focusing mode it was in. Out of curiousity though, why would one use single shot mode rather than continuous focus, if it focuses faster in continuous?
JM667 is offline   Reply With Quote
Old Mar 29, 2010, 6:59 AM   #37
Senior Member
 
shoturtle's Avatar
 
Join Date: Dec 2009
Location: Frankfurt AM
Posts: 11,348
Default

Continuous would drain the battery faster. Also if the target is stationary you really do do not need to constantly have it refocus. Here is a link to a blog that explains it better.

http://canont1i.blogspot.com/2009/12...-use-with.html
__________________
Super Frequent Flyer, no joke. Ex Patriot and loving it.
Canon Eos 60D, T1i/500D, Eos1, Eos 630, Olympus EPL-1, and a part time Pentax K-X shooter.

Last edited by shoturtle; Mar 29, 2010 at 8:02 AM.
shoturtle is offline   Reply With Quote
Old Mar 29, 2010, 8:14 AM   #38
Moderator
 
Join Date: Aug 2004
Posts: 8,529
Default

Let's clear up some misconceptions here.
First - in your example of using a 75-200mm zoom at the store. There are several factors at play. First, a lens always focuses at it's widest aperture. But consumer zoom lenses don't have constant apertures. They're usually 3.5 at the wide end and 5.6-6.3 at the long end. So, at the long end the lens is letting in half the light - so the camera will have more difficulty focusing.

Second, if you zoom in/out but keep camera focused on the same subject, some lenses are what is called Para-focal - that means they keep focus as you change zoom. Other lenses are NOT. If you switch from wide to long - even though subject is the same distance you need to re acquire focus.
Now, if you changed subjects, you also have the following issue:
if the lens is going from minimum to maximum focus distance it had to turn the focus ring the maximum amount. There are two major variables at play - first: how long does it take the camera to figure out where your subject is? and second, how long does it take the lens to focus. Going from 75 to 200mm or from 200mm to 75 you're maximizing the amount of time in that second variable. If you are only going from 75 to 80mm that second variable is a lot shorter.

Now, there's a third variable - some cameras, like Pentax, get close on focus and then make a series of tiny adjustments to lock in on final focus. That can slow things down but in general it is very accurate (for non moving subjects).

Now, Continuous focus mode is NOT faster to acquire focus. It is NOT faster when you switch subjects. The only time it is faster is if you're tracking a moving subject. Not only is it focusing continuously, but for Canon & Nikon it is doing what is called predictive focus - it does calculations to determine where it thinks your subject will be by the time it's done focusing.

And, the down side to using it is the camera will allow you to take a shot that is not in focus - unlike single shot mode it does not wait for focus confirmation before allowing you to take the photo. And, because it is constantly re-focusing and calculating where your subject will be, sometimes it gets things wrong. So, when shooting static subjects you're better off NOT using continuous focus modes. You'll be more accurate.
JohnG is offline   Reply With Quote
Old Mar 29, 2010, 9:15 AM   #39
Senior Member
 
mtclimber's Avatar
 
Join Date: Oct 2005
Location: Oregon, USA
Posts: 18,143
Default

Just another opinion, but as I own the Canon XSi and the Nikon D-500,I ran a test and they are dead even on focus times.

Sarah Joyce
mtclimber is offline   Reply With Quote
Old Mar 29, 2010, 9:21 AM   #40
Senior Member
 
shoturtle's Avatar
 
Join Date: Dec 2009
Location: Frankfurt AM
Posts: 11,348
Default

But compare to the T1i, the d5000 is slower.
__________________
Super Frequent Flyer, no joke. Ex Patriot and loving it.
Canon Eos 60D, T1i/500D, Eos1, Eos 630, Olympus EPL-1, and a part time Pentax K-X shooter.
shoturtle is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 6:54 PM.