Autofocus versus manual focus

[George Jogtich]

I have my Canon 7D and 40D with the 15 to 85 mm zoom lens.


I have been using the auto focus feature on this lens with the Canon 7D and the 40D, mainly because I didn

[TakahiroW4047]

I think for the sake of making this question easier to answer, it would be helpful to add your shooting style and autofocus mode as well []


The lighting condition at the time, how far away the subject was, with or w/o tripod, and if it was the 7D involved which one of it's numerous AF modes you were shooting with.


*edit* - Personally, unless I was shooting macro I would never use manual mode since eyeing it through the viewfinder nor the lcd is fast enough to keep up with my moving subjects.

[Trowski]

I think in general you will find that attempting to focus manually using the AF sensors as an indictor of focus will give you no better results than just using the autofocus system. In fact, likely more of your photos will be out-of-focus.


Personally the only time I use manual focus is with live view at 5x or 10x. Otherwise it is difficult to actually tell when the image will be truly razor sharp.


The autofocus system isn

[scalesusa]

I have found that using the modern autofocus lenses for manual focus, (with the exception of the big whites), is pretty difficult. Not only are my eyes getting old, but the short throw of the focus ring makes very fine focusing difficult.


With a lens designed for manual focus like the TS-E lenses, there is a world of difference. If I really wanted to use manual focus, I

[ThomasJ]

I think that the 5DII, 7D (not to speak of the XXD-Class) have poor viewf

[neuroanatomist]

I think that the 5DII, 7D (not to speak of the XXD-Class) have poor viewfínders. It's impossible to accurately focus with them - especially with lenses as fast as f2,8 (or faster)...I can't tell how a 1D(s) series viewfinder is since I haven't played with one yet.

The 1-series has slightly higher magnification (0.76x vs. 0.71x for the 5DII), and the 1-series VFs also have 100% coverage (vs. 98% for the 5DII). The 7D viewfinder has a 100%, 1.0x magnification (possible because the sensor is smaller). So from that standpoint, the 5DII and 7D viewfinders are nearly as good as it gets - you won't see a huge improvement going from 7D/5DII to a 1-series.

But maybe that optional focusing screen optimized for fast lenses helps a little?

More than a little, I believe. The standard focus screens in all current Canon dSLRs (including the 1-series) <span>have laser micro-etching designed to produce a brighter VF image, primarily to compensate for the reduced light transmission from slower lenses. So, what you see in the VF with the standard focusing screen is actually somewhere around f/2.5 even with a faster lens.


<span>You can check this for yourself - take a fast prime, hold the DoF preview button on the side of the lens mount as you close the aperture down from wide open. You won't notice the VF getting any dimmer until you hit about f/2.2-2.5.


As a side note on my 7D, even though the VF doesn't get any brighter as you go wider than f/2.2 (due to the etching to brighten up typical slow lenses), the AF points in the 7D's transmissive VF get progressively more 'washed out' by the additional light - the light is getting in there, but the focusing screen prevents it from reaching your eye.


That's the reason that, if you want to do a lot of manual focusing through the viewfinder, you really should install a focusing screen designed for it. Live View with magnification is great, but only if you have time to go that route - if you're shooting at a fast pace (e.g. portraits of kids), it can be more challenging.
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