Elan 7E low-light autofocus

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Hello everyone,

I seem stuck with a problem that may sound familiar... Canon ELAN 7E vs Nikon N80. I'm leaning towards canon:4 fps film advance (convenient exposure bracketing, great for sports) and silent mode of operation. I think I can live without a spotmeter (which Elan 7E lacks), but the reports on the Elan's sluggish low light autofocus bother me (use in theater for dance and other performances, good access). Since I can't try it out for myself, here's my question is: can a cheap (100-150$)flash (third party) provide decent AF assist without actually firing the flash when you take the shot? Thanks

-- stef jansens (bsix@yucom.be), April 16, 2002

Answers

The Canon ST-E2 is designed to do this, but it costs nearly $200. Other flash units can be made to do this as well. I know the Sigma EF-500 Super will do it for $180. other flash units can be used this way by simply covering the flash tube with black tape. Most (all?) third party falshe's AF assist lights will only be used with the central AF point, but that's the most sensitive one anyway. The cheapest way *that I know of* to cover all 7 AF points of the Elan 7 is with a Canon 420EX.

-- Jim Strutz (j.strutz@gci.net), April 16, 2002.

The Elan 7 includes a custom function which can be set (among other settings) to use AF assist but not fire an external flash. So any flash that has a usable AF assist beam should be OK.

As the previous response pointed out, the 420EX is the cheapest (and, quite possibly, only) flash unit with full coverage of all 7 AF points. The 550EX doesn't quite cover all seven points (see http://teladesign.com/photo/ef-500-super.html); no other Canon flash unit has an AF assist beam that's designed to cover more than the 5-point arrangement on the A2 and 1N. The Sigma 500 Super only covers the central point, like most if not all other third-party flash units (again, see http://teladesign.com/photo/ef-500-super.html).

-- Steve Dunn (steved@ussinc.com), April 17, 2002.


There seems to be some misinformation above.

I own and use a 550EX and an Elan 7E. The 550EX AF assist beam CAN and DOES cover all 7 AF sensors on the Elan 7E. The trick is to choose auto Area AF when you want to use the upper and lower AF sensors. Want proof? This pattern was emitted from my 550EX atop my Elan 7E:



-- Julian Loke (elan7e-owner@yahoogroups.com), April 17, 2002.

It certainly is good to know that there are affordable ways to solve the poor AF-performance in low-light levels for the Elan 7E. Thanks a lot for the information!

-- stef jansens (bsix@yucom.be), April 18, 2002.

Thanks, Julian. But note that the lines projected at the top and the bottom are horizontal, and the top and bottom AF sensors on the Elan 7e are sensitive only to lines with a vertical component. With a relatively long lens, the cross pattern for the center AF sensor should cover top and bottom, and you'll be OK; with a wider lens, I'd wonder if the AF assist beam works well.

Can you try something for me? Manually select one of the sensors (other than the top or bottom) and try to focus on an absolutely blank wall (i.e. a surface that needs the pattern of the AF assist beam). AF should be quick and reliable. Manually select either the top or the bottom sensor and repeat the test. Does it work as well as the other sensor did, work but with difficulty, or not work at all?

-- Steve Dunn (steved@ussinc.com), April 19, 2002.



Steve Dunn wrote:
Can you try something for me? Manually select one of the sensors (other than the top or bottom) and try to focus on an absolutely blank wall (i.e. a surface that needs the pattern of the AF assist beam). AF should be quick and reliable. Manually select either the top or the bottom sensor and repeat the test. Does it work as well as the other sensor did, work but with difficulty, or not work at all?

Hi Steve,

You test will not work if the top or bottom sensors are selected, since the AF pattern will not emit. If I select all 7 sensors, and use a paper mask in a Cokin P holder in front of the lens to block all but the top sensor, I can still get AF lock on my wall, but not all of the time. Naturally, the camera does better if I point the beam at a real world object with focussable contrast. Without the beam, AF was not possible. With the beam, I can get AF lock.

Even on a blank wall, you can see the texture of the wall (e.g. at the one o'clock position in my picture), which was revealed by the beam.

Also, the patterned beam is not just horizontal lines of uniform brightness. I can see detail in the pattern, which is made of slightly wavy lines with some discontinuities and occasional square boxes. This might be enough detail for phase-contrast autofocus to detect.

As for Stef's original question, I also suggest that he/she test an Elan 7E and an N80 in the shop against the new AF Sensitivity Test target at eosdoc.

-- Julian Loke (elan7e-owner@yahoogroups.com), April 22, 2002.


Here is some more information that I forgot to add:
The vertical pattern is useful for focussing at subject distances up to 2 metres (6 feet), using a lens longer than about 35mm.

Once emitted, the patterned AF assist works quite well for my Elan 7E. The problem is in making the 550EX emit the pattern.

-- Julian Loke (elan7e-owner@yahoogroups.com), April 22, 2002.


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