Blurry pictures - around 10% .Please advice on using autofocus

[rusteam]

hello,
after my photosession ,there is around 500 pics and i would say around 10% of that is blurry or out of fucus. There rest is OK.

So when i was checking which ones is blurry i came to conclusion that,
the most pictures which was blurry had F1.8 , some 3.2, some 4.5 but almost all shoots with 1.8 where blurry. The was a model in the shoot and i was at least 1.5-2 metesr from her.
So i was wondering is it because shallow depth of field and long distance to subject?
Question:
How serious relation between aperture number and distance to the subject. I bet if i would come close to my model for at least 1m - i would get some good shoots. Is'n it??

Is there any system, table how i can check what distance i should have to my object in relation to selected aperture??
I was shooting with 5dmark ii and 50 1.2 .

Also, mostly all photos with 2.8 and 5.6 and highest are sharp (some not, but i guess its my fault or autofocus).

Another question related to AUTOFOCUS:
I was shooting in Al Servo mode (for moving subjects) and i was using 1 point at a time. Usually centre point ,sometimes another point. Can utell me is it correct way to do? -
How i did it:

After framiing my model , for examaple shoulder high shoot from would say 2 m , i was using autofocus to focus on her eyes. I always trying to focus on eys. If her eyes will fall on centre AF point - i will shoot, if not i will keep camera as it is and just select ANOTHER SINGLE POINT WHICH IS CLOSEST TO THE EYES. Then press the button.

But i think its not quite correct,as a lot of time i could manage to build my frame so, that some of the point will be near eyes, sometimes they just not so close.

HELP, how is the right way to autofocus when shooting portrait? Is it nearly alwaay better to use 1 single point or its better to select all (i think there is 9 of them on 5dmii) to COVER all face? So face will be defenetly in focus??

Also how do you shoot portraits with 1.2/1,4/1.8 and manage to get model face in FOCUS?


Thank you! I'm learning and this focusing is a big issue so far. I will have another photosession soon and i dont want to end up againg with at least of 10% blurry images.


thank you!

[ElCapitan]

You have several questions there I will try to see if I can answer or at least offer some advice.

First off, f/1.8 is going to offer an incredibly shallow depth of field. I was trying to find somewhere that gives an idea of exactly how big (or in this case how small) the DOF is in millimeters. Of course this can change based on how close you are to your subject and leads to another one of your questions.

EDIT: I did find a DOF calculator. plugging in a 35mm camera, 50mm focal length, aperture of f/1.8, and a focus distance of 1.5-2m, the DOF is about 10-18cm.

The closer the lens has to focus, the shallower the DOF will be. With a fixed focal length and shooting at the same aperture, the further away your focus distance is, the deeper your DOF will become. Getting closer you your subject would only bring more areas out of focus, so you would be much better standing further back. The 5D MkII has a great resolution, so as long as you have a good exposure and good ISO, you shouldn't have any worry cropping the image down, that is if f/1.8 was the only way to get the proper exposure. If you have absolute control over the lighting, then stop the aperture down so you don't have to crop.

As for the focus points, I always suggest only using one. It gives you control over what you want the camera to try and focus on. Selecting all will not magically make the entire face in focus as the focus plane will not change. The camera/lens can only focus on one point. If you want to focus on the eyes, either use the center point and recompose or select another focus point that is over the eyes in the composition you want to use.

I don't see any problem between shooting AI Servo or AI One Shot, though if you are recomposing then AI Servo could cause some problems. Try using back button focusing and then AI Servo can act just like AI One Shot. Gets you the best of both worlds.

I have had a little experience shooting with a 50 f/1.4, and it is not necessarily the wide maximum aperture that makes it a great lens. Primes are great for several reasons. One is that they can be very sharp from center to edges, but possibly when only the aperture is stopped down a bit. The other reason they are great is because they do allow you to shoot in low light conditions without bumping up the ISO to high. When given great lighting or in control of lighting, that 50 is going to be amazing.

Here is an example of a portrait I took with the 50 f/1.4. It was shot in a studio with an ISO of 200 and an aperture of f/11. I have a hard time finding anything out of focus on the model's face, let alone the entire model. I was only standing about 5 feet from the model.

[rusteam]

Originally Posted by ElCapitan

You have several questions there I will try to see if I can answer or at least offer some advice.

Thank you for your reply. Nice picture!

What is the minimum aperture u usally use for portrait work? 2.8? As far as i understand .. not many people jump below 2.8 in portraiture isnt it? And because they want to be safe in focus area? Correct?
What is the usual apertures when you shooting people outside?

Another question - a bit confused here. People raving abt 1.2/1,4/1.8 lenses as they have great low light capabilities .Ok ,i know that. Now , if i will be shooting with this lens on a wedding ceremony for example without flash - how i will take advantage of this lenses??

If i have 50 mm 1.2 to take advantage of it i need to use apertures 1.2 - 1.8 to get my lens act beautifull in low light? Or it doesnt matter , i can shoot on F 5.6 for example but low light will be much better then if i will shoot with, for example 70-200 f4 set to 5.6 ???? Basically:
50 f1.2 set to 5.6 and an other lens for example 70-200 f4 set to 5.6 will be the same in low light or not???
I cant believe that photographers gona shoot ceremony with apertures 1.2 - 1.8 . ..!?

[ElCapitan]

A 50 at f/1.2, 1.4, or 1.8 isn't necessarily more beautiful at those apertures compared to shooting the same lens at f/8. What it does is allow more light to the sensor so you can shoot at a higher shutter speed and lower ISO. A possible downside is the shallower DOF, unless you want that shallow DOF, then it isn't a downside at all.

When you say wedding ceremony, I am assuming you are talking about group shots, candids, and maybe wide establishing shots. If the light is really low and you are not using a flash, then you will have to use the lowest aperture/highest ISO combination to get a fast enough shutter speed.

Remember, the closer your subject is, the shallower the DOF will be. Try to put a little distance between you and your subject(s). If that isn't possible, then you probably need a flash so you can stop down the aperture.

[ravncat]

You have to be careful with autofocus at apertures bigger than 2.8 Most camera systems are designed for 2.8 in the viewfinder and for AF. As a result, it's easier to miss focus, especially if the AF system is not in good calibration. Most likely - the results that are blurry are either misfocused. (Or your shutter speed was too long)

[LanceH]

Here's a link to a popular DOF calculator. On the left sidebar you'll find some links to articles on DOF and hyperfocal distance.

If I plug in some typical conditions you mention (Canon 5D MII, 50mm, f1.8, 1.5m to subject) the DOF is about 9.3cm or 3.7 inches. If the model was standing still this should have been enough to at least get the eye in focus but maybe not the entire face.