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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[HDNitehawk]

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

Neuro


While you have the numbers right, however from first hand experience now with my new 1D Mark IV I can say there is a substantial improvement. First day out of the box I was able to do something I had found difficulty doing with the 5D and 7D. A bird in the bush, which the focus lock couldn't hit, I switched to manual focus and took several pictures of it tack sharp. With the 5D and 7D I always had much more difficulty, and what would seem in focus most of the time turned out to not be. In this regard have found the 1D Mark IV superior. (possibly a different focusing screen comes with it than the 7D or 5D, or maybe it is just superior, it does seem to give you more view)


I do not remember the why's or how's of what I read, but from what I understand the viewfinders of the new digital cameras are not as good or clear as the old film cameras. With the addition of all the new AF systems I guess the designers didn't see fit to keep manual focus as a premium option on the new digital cameras. Its a shame with all the new Ziess lenses like the new 35mm, 21mm and the 100mm Macro that appear to be very good.

[Sheiky]

I use MF from time to time. I don't think it's more accurate, but it's way better than AF in some occasions. About two weeks I encountered a deer from very close, but it was in the bushes/weeds so there were a lot of foreground elements and the AF kept focusing on those rather than my subject. In that case, MF was the only way I could have gotten it to focus correctly and it worked razor sharp.


However I shot the photos at f4 and f5.6. At those apertures it's not hard to see the exact focusing plane. I have used MF before on apertures like f1.4 and f2 and such and the viewfinder of the 5DII or focusing glass is definitely not reliable for those kind of apertures. It lookes sharp in the viewfinder, but the results weren't. Read above for more technical info about that [] I do think that you could use MF on wider apertures like f2 and such, in combination with the AF confirmation lights. (the red squares) that is if your lenses are calibrated correctly to your camera.

[Trondster]

I exchanged my Eg-A standard focusing screen on my 5DmkII with the super matte Eg-S, and got a huge difference. With the standard focusing screen I could not see much change in the depth of field in the viewfinder from f/1.4 to f/2.8 when stopping down, but with Eg-S I can really see where the focus plane is on fast lenses. You get a lot more precision assessing the focus in the viewfinder on fast lenses, at the expense of light. My old f/4.5-5.6 kit zoom is now noticeably dimmer in the viewfinder when shooting indoors - Canon recommends using f/2.8 or faster lenses with a -S focusing screen.


For perfect focus for non-moving subjects I use liveview and 10x zoom.


The little squares in the viewfinder use the exact same phase detecting sensors for determining focus as the autofocus uses, so the sensors are not inherently more accurate when in manual focus mode. The advantage of using manual focus is to have more control of where to place the focus, as you know the artistic context of how the picture should be composed - you know if it is the deer in the background or the branches in the foreground that you want to have in focus..


With a slow lens (aperture wise) as 15-85 I doubt that you would see that much difference in the viewfinder with different focusing screens - you

[Jon Ruyle]

While you have the numbers right, however from first hand experience now with my new 1D Mark IV I can say there is a substantial improvement.

Interesting. I had the opposite experience: I found it easier to judge focus with the 5DII than the 1DIIN because of the larger screen of the 5DII. But then, that was a 1DIIN, not a 1DIV. Dunno what improvements there were, if any, though.