Is this really a front focusing problem?

Hi guys,
I need some help over here. I bought a digital rebel a few weeks ago. I was taken lots of pictures and life was good. Then, I tried to take some portraits and noticed that they always were blurred.

I decided to do a little test putting Lego people and trying to take a picture, focusing on the lady that is right in the middle (red hair). I didn't try to use manual focus (since my understanding is that the front focusing problem only occurs with autofocus... but please let me know if I'm wrong!)

These are the results:

1. Using a Canon 50mm f1.8 II on a tripod and using the timer to avoid camera shake:

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Well, neither one of those pictures look focused on the lady LEGO.

As far as the guy telling about the autofocus not being accurate, he is just plain stupid for even thinking about saying that to someone. I suggest you find another camera shop to go to with knowledgable people.

Yeap, I know.... when he told me that about the autofocusing, I sent an email to Canon Canada to see what they think about this "authorized dealer"

Hi Imelendez,

nice group photo you have there...

some ideas ...

Well, if your eyes are off, the problems would also occur with manual focus

I am not an expert either, but this sounds like total BS to me.

The camera has a very shallow depth-of-field (that means the part of the picture that is sharp and in focus as opposed to the parts of the image that are blurred) at 1.8. However, there are the 50/1.4 and 85/1.2 lenses that are used with very good results on the 10D and DRebel. To tell you that you always should focus manually is simply wrong.

To tell that, you must be sure that the camera really focused on the lady, and not on something else. You really can't tell where the camera focused. The only way you can assure that the camera focused exactly where the lady was standing would be to use some kind of isolated target at the same distance. Put up a vertical cardboard piece with a black line pattern that you can use for focusing exactly above the lady and focus on that.

No, but the DOF is very shallow, so that you'll see easier if the AF is off. The AF will be inaccurate, if there is too much light available. Actually, the 50/1.8 lens will focus better than the 18-55 lens, because it lets in more light.

Hope that helps a bit.

Best regards,
Andy

What settings were you using? A small Av could have led to the first bad pic. Different values and AF points can lead to those results. Or was everything manual?

Thanks for the answers guys...

Andythaler, I'll do the test that you suggest. But the part that makes me sad is that I'm pretty sure that It was focusing on the lady...but when I saw the pictures in the computer, was always blurred (please note that I need several tests with different settings, but at f1.8 had the worse results)

I had the camera in av, f1.8 and 1/2 secs (I think). AF Point was right in the middle, and the red dot was right in the middle of the "red hair" lady.

2 things ...

... select a higher ISO (e.g. 800 or 1600) in order to get a faster shutter speed (at least 1/50) . Even on a tripod, camera shake can not be ruled out. Turn on all the lamps you can mobilize to help the camera focusing.

... you should be aware that the area the camera actually uses for focusing is larger than the red dot that is displayed.
The dot is in the middle of the focus area, but the actual area might cover more of the figures.

Given your preference for LEGO, I'd suggest you create the focusing pattern by putting 2 blocks (4x2) side-by-side and creating something like a cross:

white black
white black
white black
black white
black white
black white
......xx
......xx
......xx
......xx
......xx


The xx block stands for the stand, but I think you get the picture

Put it to the side of the lady so the front of it is in one pane with her face. It should also be away from the figures so you only focus on it.

Best regards,
Andy

Interesting... I'll do that as soon as I get home and give it a try. I repeated the same group picture with another Rebel in the store and the results were a bit better... but still, I just want to make sure that if I send the camera to Canon (and wait 2 month)... it will be because something is indeed wrong.

I find that sometime when trying to focus on a smooth and shiny object at close range the AF sensor gets fooled into thinking the focus is dead on and in reality it is not.

I shoot a lot of product shots for a stock photo agency and the way I do it when having a focusing issue is hold a small feather against the shiny object and focus on it. Then move the feather and shot. I also use only the middle AF sensor.

Personally i'd try a smaller aperature, as it partially looks like a depth of field problem. Parts of the photo are focussed ok, but it looks like a narrow DOF. F8 might be worth a go. Try on auto and manual focus.

Well, the whole point of the exercise is to use as large an aperture as possible to see whether the camera focuses correctly
Best regards,
Andy

Hey imelendez,

we want to see the Lego people again

Best regards,
Andy

Hi Andythaler...
I've been really busy at work and haven't had the time to set up the test. If I'm lucky, the next day or two I'll have sometime to keep testing. And just as an update, Canon Canada sent me an email saying that they are not aware of any issues with autofocus

I sent them an email after the "expert" at the camera shop told me that the camera cannot focus when the apperture is 1.8

Anyway, I'll post the results soon!!!

Thanks for the help

Leo.

Hi again,
So I finally had the chance to do the test that Andythaler suggested me (well, sort of... my daughters let me used all the figures this time :lol

All tests were done using a Canon 50mm f1.8, with the lego and the camera on top of a table, using the timer to avoid camera shake. Lego blocks were aprox 30cms from the camera.

1. f1.8 1/13 s (800x600)

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Hi Imelendez,

Maybe my first post was not clear enough.

If you want to be sure where the camera focuses, you should make a focusing target that is in a different place from the objects you want to check for sharpness.
Also, you might try to introduct both horizontal and vertical lines in the focusing target.

TARGET
TARGET ...< - Focus on this area here
TARGET
TARGET ...............Test the results below
TARGET ............... VV
....I
....I...............o.​...........o..........​...o............o.....​......o
....I...............o.​...........o..........​...o............o.....​......o
....I...............o.​...........o..........​...o............o.....​......o
....I...............o.​...........o..........​...o............o.....​......o
....I...............o.​...........o..........​...o............o.....​......o
....I...............o.​...........o..........​...o............o.....​......o


Also, you might use objects that have a little more detail where you could judge the sharpness ... the little people were fine for that.

One last thing ... 30 cm is really close to the camera. What is the minimal focus distance of the 1.8/50 lens? I would put the camera further away from the target. This will also allow you to judge the focus better, as the DOF will be even shallower on f/1.8

Besides, I like them

Hope this helps.....

Best regards,
Andy