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paulselhi
12th of November 2004 (Fri), 08:06
I have seen variuous digital reviews that state that such and such a camera has autofocuus but some do and some don't have an AF lght

What exactly is the role of the AF Lght ? Is it a big plus to have it or a big minus to lack it ?

Jesper
12th of November 2004 (Fri), 08:42
AF systems don't work well when there's not enough light.

Look at the following explanation: AF Assist (http://photonotes.org/cgi-bin/entry.pl?id=AFassist)

The AF Assist light helps the AF system when the ambient light is very dim. By illuminating the subject with a small light, it's easier for the AF system to lock on to it.

It's certainly an advantage to have it, especially if you want to do low light photography. Note that many Canon speedlites have a red AF Assist beam, which does the same as an AF Assist light on the camera itself.

paulselhi
12th of November 2004 (Fri), 08:45
i thank you, i wonder how such a small LED can contribute to lighting ?

PacAce
12th of November 2004 (Fri), 08:58
i thank you, i wonder how such a small LED can contribute to lighting ?

Not all AF assist lights provide lighting of the subject. Some of them just provide a pattern of light on the subject and this pattern is what the camera picks up and focuses on. In this case, the light does not have to be intense enough to light the subject but just bright enough to provide a pattern with some contrast that the AF system can lock in on.l

paulselhi
12th of November 2004 (Fri), 09:03
ahh.... rather like a lazer targeting system ?

PacAce
12th of November 2004 (Fri), 09:43
ahh.... rather like a lazer targeting system ?

Yup. Brings to mind that TV show on the Discovery Channel, "Tactical to Practical". :)

robertwgross
12th of November 2004 (Fri), 13:32
(an old anecdote)

I had my D60 hung around my neck, and I was poking into some old mining ruins a little bit north of Belmondo. I didn't have any flashlight with me, since I did not expect to be going into anything dark. Well, lo and behold, a huge mine opened up before me. After a minute or two, my eyes were adapting to the dim light, but as I went deeper and deeper, I was afraid of stepping into some bottomless pit. I then started half-pressing my camera's shutter button. In the darkness, its flash head came up, and then the white AF assist lamp was turning on for about one second per press. That wasn't enough light to really go anywhere with, but at least I could see what I was stepping into.

If the camera had the red pattern assist light, it wouldn't have worked so well, just for that purpose.

---Bob Gross---

paulselhi
12th of November 2004 (Fri), 14:21
Hmmm ..wandering around in dark and old mineshats with only a camera for lighting ?

Call me a wimp but i think that that would be too much for me !!!

I need ropes , helmets, outrageoues shiny climbing gear,wet suits, comforatble pubs, more ropes ooh and lots of lights !!!

PacAce
12th of November 2004 (Fri), 14:27
(an old anecdote)

I had my D60 hung around my neck, and I was poking into some old mining ruins a little bit north of Belmondo. I didn't have any flashlight with me, since I did not expect to be going into anything dark. Well, lo and behold, a huge mine opened up before me. After a minute or two, my eyes were adapting to the dim light, but as I went deeper and deeper, I was afraid of stepping into some bottomless pit. I then started half-pressing my camera's shutter button. In the darkness, its flash head came up, and then the white AF assist lamp was turning on for about one second per press. That wasn't enough light to really go anywhere with, but at least I could see what I was stepping into.

If the camera had the red pattern assist light, it wouldn't have worked so well, just for that purpose.

---Bob Gross---

Sure it would have, Bob. If you didn't see any red patterns at all on the ground directly in front of you, then that's would have been a sign not to take another step forward. :lol:

paulselhi
12th of November 2004 (Fri), 14:34
But you cave your head in hitting a low beam !!!

PacAce
12th of November 2004 (Fri), 14:50
But you cave your head in hitting a low beam !!!

As long as the camera is safe and sound, that's OK. Cameras are very sensitive to shocks like that but to a hardheaded person, that'd be just like a love tap on the forehead. :lol: :lol:

Jesper
13th of November 2004 (Sat), 02:19
(an old anecdote)

I had my D60 hung around my neck, and I was poking into some old mining ruins a little bit north of Belmondo. I didn't have any flashlight with me, since I did not expect to be going into anything dark. Well, lo and behold, a huge mine opened up before me. After a minute or two, my eyes were adapting to the dim light, but as I went deeper and deeper, I was afraid of stepping into some bottomless pit. I then started half-pressing my camera's shutter button. In the darkness, its flash head came up, and then the white AF assist lamp was turning on for about one second per press. That wasn't enough light to really go anywhere with, but at least I could see what I was stepping into.

If the camera had the red pattern assist light, it wouldn't have worked so well, just for that purpose.

---Bob Gross---

So..... are you telling Paul to look for a camera with a real, white AF Assist lamp, because that may one day be useful when he wanders into a dark mine without a flashlight...?? 8) :lol:

robertwgross
13th of November 2004 (Sat), 13:23
So..... are you telling Paul to look for a camera with a real, white AF Assist lamp, because that may one day be useful when he wanders into a dark mine without a flashlight...?? 8) :lol:

Paul is from London. How many gold mines does he find in London?

---Bob Gross---

Jesper
13th of November 2004 (Sat), 15:47
Some additional thoughts: There are at least three kinds of AF assist lights in Canon EOS bodies.

1. A small, white LED. I don't know which bodies have this, but the DSLRs (at least the 300D, 10D, 20D) don't have this. Advantages: works well, disadvantages: the white light could be mildly disturbing for your subjects.

2. The red AF assist beam that EX speedlites emit. Advantages: works well, and doesn't disturb your subjects. Disadvantages: You can't use it as a flash light when you're in a dark mine.... ;)

3. Some EOS bodies (300D, 10D, and also my EOS 30 / Elan 7E) use the popup flash for AF assist. When the camera is in "auto" mode (not the creative zone modes) and when the light is too low, it pops up the built-in flash and emits a series of pulses to assist the AF. This is VERY annoying and disturbing to your subjects...... :( I wonder why Canon came up with something as stupid as this instead of a simple LED....

Jon
13th of November 2004 (Sat), 16:01
So..... are you telling Paul to look for a camera with a real, white AF Assist lamp, because that may one day be useful when he wanders into a dark mine without a flashlight...?? 8) :lol:

Paul is from London. How many gold mines does he find in London?

---Bob Gross---

OK, stumbling around Gringotts' vaults, then . . . or the London sewers (cf. Sherlock Holmes).

vfilby
13th of November 2004 (Sat), 18:32
You know, a flash light (a little mini-maglight) is something I started carrying in my pack. It has been immensely useful. I strongly recommend everyone toss a small light into their gear bag. (even the micro maglights that are only alittle bigger than a AAA battery).

And I would say especially for you Bob, with your penchant for dark, shady places and such. ;-)

robertwgross
13th of November 2004 (Sat), 22:20
After the gold mine experience, I attached one of those little LED squeeze lights onto my camera case.

---Bob Gross---

Andy_T
14th of November 2004 (Sun), 17:13
Some additional thoughts: There are at least three kinds of AF assist lights in Canon EOS bodies.

1. A small, white LED. I don't know which bodies have this, but the DSLRs (at least the 300D, 10D, 20D) don't have this. Advantages: works well, disadvantages: the white light could be mildly disturbing for your subjects.


This system is used on the powershot digicams.

The white LED is a little off-center and has the purpose to display a vertical line (between lighted and not lighted area) that the image sensor can pick up. It's not that bright really and works only moderately well over short distances.

Best regards,
Andy