Auto Focus When Shooting Portraits

Hi All,

I have been having issue's getting correctly focused eyes when shooting portraits. I am using a 300D, EF50 F1.8II, 420EX (bounced) flash, manual mode - 160th shutter speed and an aperture of F2.8 for shallow DOF.
My technique is to focus on one of the subject's eyes using the centre focusing point and then recompose and fire the shutter. The problem is that the eyes are not sharp. Some times the ears look really sharp and other times the tip of the nose seems to be the sharp point of the image.

I have read that the actual focus sensors are bigger than the marked areas within the viewfinder and that the sensor is possibly focusing on another point other than the eyes but it is hard to judge this through the viewfinder.

What technique do others use for portraits to achieve sharp focus on the eyes?

Manual focus.....

I've had the same issues with the 50mm f1.8. Focus seems hit and miss on this model.

I think you're putting too much blame on the lens. The focus/recompose technique is not a good idea, ever, because you always slightly shift the angle of the camera. This can have larger effects than you might expect.

On the 300D manual focusing is not a good idea either, unless you have amazing ability, because the viewfinder is far too small and dark.

Try using a different focus point just for reference and see if the results get any better.

Manual focus.

Another vote against focus-recompose and manual focus.
Select the focus point that's closest to your subjects eye so you don't have to re-compose.

And use the * button to focus.

Best regards,
Andy

I don't think * works for focus on the 300d

drewmk2 wrote:
I don't think * works for focus on the 300d

You're right, it will not work - even with the Wasia hack.
Thank you for pointing it out.

Best regards,
Andy

I've been thinking about this last time on my last for fun photoshoot, focus then recompose it will be slightly differnent, I've started using other focus points again and what a differnce, (also I've upgraded from the 350d to the 30d the focusing points I find are located in better areas? than the 350d.

Manual Focus, I only do that with my contax lens, otherwise MF is a pain

When shooting portraits, especially half body shots or headshots with shallow DOF, the subject is so close that the focus, lock and recompose method often gives inaccurate results. IIRC one of the canon guides state that anything under 15ft is affected by shallow depth of field effects if FLR is used. It's much better to pick the point nearest to the eyes or better yet if one of the AF points fall on the eyes.

I find that it helps to pick the outside corner of the eye so that the AF point registers the contrast difference.

I've read that the 50 f1.8II AF is not always accurate, but i guess this varies with each copy. i'ev never had a problem with mine, but my 50f1.4 seems a little more consistent. do a lens test and you'll more or less know if it's your lens or not. I'm guessing not because very little goes wrong with a prime.

MF is difficult on my 300D because the viewfinder is small and the AF points are so much smaller than my 1-series cameras that i just use AF all the time. I just try to get a proper lock before i take the shot.

Thanks for the replies, have tried using another focus point to eliminate focus recompose but the problem still exists. I guess the camera is grabbing a point of higher contrast outside of the marked sensor box.

The lens and camera have both been checked by Canon and are reported to be within specifications.

As stated in one of the replies manual focus is not an option due to lack of viewfinder brightness/size.

I just did a focus-recompose photo shoot. Now I want to do a nearest-focus point shoot. But, also, I noticed that it is extremely hard to keep proper eye focus at 2.8. The DOF is so shallow that the slightest of movement of subject or photographer (I was handholding with a 70-200 IS) can be a miss.

While you may enjoy the effect of the extreme background blur, to me unless both you and your model are very skilled and controlled it isn't worth it for what you lose in the eyes. I would stop down to around 4 or so, to increase the depth. For now.

In the long run, my plan is to get better at holding the camera.

The way you recompose matters. If you only move up and down, side to side so that the subject stays exactly the same distance from the lens you are fine.

If you move the lens at an angle and are close enough to move the subject out of the plane of focus you'll see a difference. It will put either the nose or the ears in focus depending on the angle. Make sense?

A bit of mathematics is in order here.
A 50mm lens at f/2.8 on a 1.6 crop camera, at a reasonable portrait distance of 8 feet, would give you a near DOF of about 4 1/2 inches and a far DOF of about 5 inches. If you move the center focus point a foot to focus-recompose, the inaccuracy of the triangulation would only be an inch or so, which would be well within the DOF. For that matter, focusing on the tip of the nose or an ear would probably be close enough that you can't tell the difference.

I have never used the 50mm f/1.8 lens, but from its reputation I think it could be the culprit.

Most anyone who has used the 300D would agree that pin-point manual focusing is not an option, at least not with the stock focusing screen. I think the OP's best option, short of upgrading in the lens department, would be to use a smaller aperture in these situations. Taking multiple shots while refocusing between shots would also be advised.

Curtis - a big thank you for this. Math wins every time. I knew this but couldn't prove it and didn't want to take the time to do the math. DOF is your friend in these situations. Unless you are shooting razor thin DOF a bit of recompose shouldn't be noticeable IMO. And I did say 'a bit'....

And you are correct about the 50mm f1.8. It's a fun lens but not exactly dependable where repetition is needed.