Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Canon EOS dSLR

Reply
 
Thread Tools Search this Thread
Old May 23, 2011, 12:39 PM   #1
Senior Member
 
eugeniogurrea's Avatar
 
Join Date: Apr 2010
Location: Bahía Blanca, Argentina
Posts: 184
Default AF Assist Beam in Canon Models

Does anybody have an idea about why Canon keeps using Intermittent firing of built-in flash or by optional dedicated Speedlite to generate de AF Assist beam?

Is tahat a pain in the ass? or cause no trouble?

I'm not a Canon DSLR user, but every time a check canon's specs, I see that detail...
eugeniogurrea is offline   Reply With Quote
Sponsored Links
Old May 23, 2011, 1:16 PM   #2
Moderator
 
Join Date: Aug 2004
Posts: 8,497
Default

I have to say, it's not a big issue. If you really want photos of a quality equal to using a DSLR and you want flash, using a speedlight is the proper way to go anyways. The built-in flash on a dslr should be used for emergency use only.
JohnG is offline   Reply With Quote
Old May 23, 2011, 2:51 PM   #3
Senior Member
 
frank-in-toronto's Avatar
 
Join Date: Mar 2010
Location: Toronto Canada
Posts: 1,083
Default

Personally, i turn off the AF assist. I hate to see someone who is pretending to be an accomplished enthusiast photographer point a dslr with a glaring red AF assist. The cameras that use the flash are even worse. Another pet peeve is the beep-beep in quiet rooms. Maybe it's just me, but I don't have a problem getting AF lock except in the darkest of rooms.
frank-in-toronto is offline   Reply With Quote
Old May 24, 2011, 7:06 AM   #4
Moderator
 
Join Date: Aug 2004
Posts: 8,497
Default

Quote:
Originally Posted by frank-in-toronto View Post
Personally, i turn off the AF assist. I hate to see someone who is pretending to be an accomplished enthusiast photographer point a dslr with a glaring red AF assist.
Guess we'll have to disagree. AF Assist is there for a reason - to help make the best photo possible. The "glaring red AF assist" is minor compared to the flash itself. The point is to make great photos and the AF assist helps do that. It's perfectly fine that you don't like to use it. I just disagree with the assertion that using it is an amateurish move. In my experience I've found it extremely beneficial as it speeds up the AF lock which is what you want. Different strokes for different folks
JohnG is offline   Reply With Quote
Old May 24, 2011, 8:26 AM   #5
Senior Member
 
eugeniogurrea's Avatar
 
Join Date: Apr 2010
Location: Bahía Blanca, Argentina
Posts: 184
Default

What I'm trying to mean is that I don't get the reason why Canon uses as AF Assist a flash strobe and not a red or white/blue LED, just like in the G11...

Because using the flash implies having it pop up, and besides i'm not a DSLR current user, I think that won't be 100% comfortable...
eugeniogurrea is offline   Reply With Quote
Old May 25, 2011, 2:07 AM   #6
Super Moderator
 
peripatetic's Avatar
 
Join Date: Nov 2004
Posts: 3,595
Default

But it doesn't fire a pre-flash for AF assist on the DSLRs on any model I've ever used.

If you have an external flash attached then it uses the IR beam, which in the dark you can see as a grid overlay on your subject to get focus, and it's very accurate.

You'll need a flash expert to tell you, but the pre-flash might be if you are trying to do non-TTL flash exposures or triggering multiple units.

NHL - help us out here. I'm not sure what the OP is talking about.
__________________
My gallery
My X100 blog
peripatetic is offline   Reply With Quote
Old May 25, 2011, 5:17 AM   #7
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 10,906
Default

Quote:
Originally Posted by peripatetic View Post
NHL - help us out here. I'm not sure what the OP is talking about.
I believe eugeniogurrea is talking about the AF assist lamp which is present on some Nikon's and not Canon's dSLRs...
-> It's a bright LED which illuminates the scene (like some camera phones) rather than flashing the built-in flash or uses the IR focusing beam from the speedlight

I'm with everyone on this as most dSLRs do not need any AF assistance, even in the darkest room (as I always turn this camera setting off), if you point the camera to details where it can focus on...
The IR beam will help the camera focus on featureless blank wall where there's nothing for a dSLR to pick on (The Nikon's AF assist beam also does not work in this case so you'll also need to use the IR from its speedlight).
If the subject has low-contrast (especially in the dark) then the IR beam is the best because it'll speed up the AF greatly that's why all the external flashes have them, as you don't need any detail for the camera to focus on (The projected IR pattern lines are the contrasting details)


Quote:
Originally Posted by eugeniogurrea View Post
What I'm trying to mean is that I don't get the reason why Canon uses as AF Assist a flash strobe and not a red or white/blue LED, just like in the G11...

Because using the flash implies having it pop up, and besides i'm not a DSLR current user, I think that won't be 100% comfortable...
IMO you'll find that a Canon dSLR will focus faster in the dark without any assistance than a G11 with its AF assist beam enabled!

-> The G11 is based on the camera sensors detecting contrast (which does not work well in low-light) whereas a dSLR uses phase-detection with a separate high-speed split-beam module inside the viewfinder for its focusing which will work even faster with lens of f/2.8 aperture or higher...
__________________
photos (ϕοτοσ), light
graphos (γραϕος), painting

Last edited by NHL; May 25, 2011 at 5:37 AM.
NHL is offline   Reply With Quote
Old May 25, 2011, 8:50 AM   #8
Senior Member
 
PeterP's Avatar
 
Join Date: Jul 2003
Location: Ontario, Canada
Posts: 3,363
Default

The strobes pre-flash in the canon DSLR's is not for AF,
it is the camera/flash working out what the correct TTL flash setting should be for the shot.
(I think Nikon does the same thing)

My ancient eos 10s (film camera) had a dim red, more infrared assist light.
It was actually very useful, not for focusing but some birds found it very interesting and wanted to investigate it.

Quote:
Originally Posted by eugeniogurrea View Post
What I'm trying to mean is that I don't get the reason why Canon uses as AF Assist a flash strobe and not a red or white/blue LED, just like in the G11...

Because using the flash implies having it pop up, and besides i'm not a DSLR current user, I think that won't be 100% comfortable...
Last thing I would want is a bright anything going off in many situations I do not want to become centered out and noticed.
__________________
Peter

Imaging is all about light and your ability to sculpt it.
Equipment is just a secondary nuisance.

Last edited by PeterP; May 25, 2011 at 8:52 AM.
PeterP is offline   Reply With Quote
Old May 25, 2011, 5:08 PM   #9
Senior Member
 
eugeniogurrea's Avatar
 
Join Date: Apr 2010
Location: Bahía Blanca, Argentina
Posts: 184
Default

Perhaps I'm not understanding the whole thing....mainly due to my ignorance in this topic.

Checking what Canon says for example for the T3i specs, it is:
"AF Assist Beam:
(1) Intermittent firing of built-in flash
(2) Effective range: Approx. 4 m/13.1 ft at center, approx. 3.5 m/11.5 ft at periphery

* With an EOS-dedicated Speedlite attached, the Speedlite's AF-assist beam is emitted instead.
* Compatible with assist-beam (intermittent firing) of 320EX, 270EX II and 270EX flashes."


I understand that as the G11 fires a bright LED to help the AF, the DSLRs fire a flash strobe, but in that case, in order to have the AF assistance, you have to pop up the built in flash, in other case you won't get the assistance....am I right?

It is not a major topic, but I think it won't be comfortable to be having the built in flash pop up al the time, just in case you will need the AF assistance...

Regards,

Eugenio
eugeniogurrea is offline   Reply With Quote
Old May 26, 2011, 9:24 AM   #10
Senior Member
 
PeterP's Avatar
 
Join Date: Jul 2003
Location: Ontario, Canada
Posts: 3,363
Default

Ah, that is completely different than in my bodies

None of mine have a built-in popup flash, and the 580EZ speedlights have a red window on the front that projects a red grid pattern for af assist.
I believe the 430EZ speedlight also as the red af assist window.

According to this article almost all canon speedlights have the red af assist window, but it does not work on all firing modes.
Go down to the "AF assist light" section in this article to read more about it.
http://photonotes.org/articles/eos-flash/index3.html

According to it the 270ex is the only one in the group that has no red af assist window and will pulse the main tube to gain focus
The 320ex is not listed at all, maybe it is another one that pulses instead of having a red af assist light.
And yes I agree that would be a very annoying feature to have !
__________________
Peter

Imaging is all about light and your ability to sculpt it.
Equipment is just a secondary nuisance.

Last edited by PeterP; May 26, 2011 at 9:35 AM. Reason: fixin grammer
PeterP is offline   Reply With Quote
0
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 9:16 AM.




SEO by vBSEO 3.6.0 RC 2