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Old Mar 2, 2012, 1:47 AM   #1
BDD
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Default AF-Illuminators in hi-end cameras

In anticipating the 5D3 all these weeks...waiting for leaked specs...and now knowing what the 5D3's feature list includes (being as it was just announced today)...hoping for good native ISO range...seeing that the 5D3 offers 100-25,600...I just realized it has no AF-illuminator (nor does the 1D-X or Nikon D4). Why would they omit this in hi-end cameras touting their ability to shoot in low light?? Is having an AF-illuminator not vital?
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Old Mar 2, 2012, 6:10 AM   #2
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The AF systems in dSLR models at that level are very good, so you can still focus in relatively low room light without an AF illuminator.

But, not having an AF illuminator is normal for camera models do not have a built in flash (and the models you're mentioning do not have a built in flash)

If you're shooting in conditions where you need a flash, then a dedicated flash with an AF illuminator built into it would be used.
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Old Mar 2, 2012, 10:08 AM   #3
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That would explain why Canon & Nikon chose not to have AF-Illumination in their flagship (and hi-end cameras like the new 5D3). Especially when one of their key features is their ability to shoot in extremely low light. Hence their wide native ISO ranges (e.g. 1D-X with 100-51,200 and the 5D3 with 100-25,600).

At the same time it's interesting that the new Nikon D800 DOES have AF-illumination...no pop-up flash...and not a wide native ISO range (100-6400 native). Why did Nikon deem it necessary in this case?

And while there will be situations where using an external flash would be advisable (e.g. subject against bright background) there are times when you are in a low light situation (e.g. temple lit only by candles and a little ambient light from the doorway) where you are not permitted to use flash and still want that shot. Hence these wide native ISO cameras.

When they test the 5D3, 1D-X and D4...I hope they test the limits of low light shooting. Which they probably have done with the D3s (100-12,800 native ISO)...Guess I should Google some D3s test reports...

Last edited by BDD; Mar 2, 2012 at 10:22 AM.
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Old Mar 2, 2012, 11:08 AM   #4
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Judging from your previous posts, you have a Nikon D300. It should be capable of focusing in light levels as low as -2EV with a 50mm f/1.4 lens on it from tests I've seen. The only site I'm aware of that tests AF in various light levels is http://www.popphoto.com , and you'll see that in it's review tests results. They use a 50mm f/1.4 (when available for a model being reviewed) for their AF tests, and graph AF speed at various light levels.

You'll find the same kind of results for models like the D3/D3s, and the newer Canon and Nikon Pro grade models should also be able to focus in light that low (provided you have a brighter lens on them with a subject that has sufficient contrast).

That's relatively low light (a typical home interior at night as around EV 5 (a *lot* brighter than -2EV). ;-)

To put that into perspective, you'd need an 8 shutter speed for a properly exposed image using ISO 100 with an aperture of f/1.4 at -2EV light levels. More about Exposure Value here:

http://en.wikipedia.org/wiki/Exposure_value

If you google for EV calculator, EV chart, or similar, you'll find lots of pages with more examples of how much light is present in typical conditions. Here's one page with some tables on it:

http://www.fredparker.com/ultexp1.ht...ensity%20Chart

Here's an online calculator:

http://www.calculator.org/calculate-.../exposure.aspx

Now, are you going to find conditions where a camera can't lock focus? Sure. For example, perhaps you're outside at night away from city lights. But, for the most part, the AF systems in modern mid to pro grade cameras are good enough so that an AF Assist Lamp isn't necessary in most conditions you're shoot in (including dimly lit interiors) with a brighter lens on them; and you can always use the AF assist lamp on a hotshoe attached flash if using a camera that doesn't have one built in.

Try turning off your D300's AF assist lamp, and I think you'll find your camera is still able to lock focus in relatively low light with a brighter lens on it, and you'll see the same thing with most modern dSLR models.

The Pro grade models tend to have more sophisticated AF systems (number and type of AF points, better tracking algorithms with faster internal processing, and faster AF speed, etc.). But, even the mid range dSLR models from major manufacturers will tend to be able to lock focus in light levels down to 0EV or lower within 1 second with a bright lens like a 50mm f/1.4 (and the brighter the light the faster the lock time).
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Old Mar 2, 2012, 11:22 AM   #5
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BTW, if light is so low that locking focus is an issue, another trick is to use a hotshoe attached flash model's AF assist lamp without firing the flash if you want to shoot by ambient light only. With some flash models (for example, a Nikon SB-600), you can disable the flash part in it's menus and still use it's AF assist lamp.

With other cameras (for example, some of the Canon dSLR models), you can accomplish the same thing via a Custom Function (where you disable the flash via a camera setting, but still allow the AF assist lamp to work).
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Old Mar 2, 2012, 11:57 AM   #6
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Ok thanks for your help JimC. Will keep your ideas in mind. Was about to ask you about using the AF-Assist on the external flashes w/o firing the flash.

It's no wonder Canon & Nikon (and others) have chosen not to include an AF-illumination feature on their higher-end extended native high ISO (5D3, 1D-X, D3s..etc.) cameras.

You have a good memory...remembering I'm a D300 owner.

Last edited by BDD; Mar 2, 2012 at 12:01 PM.
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