My first 300D car pics, i also have a focusing problem

[eyst]

Hey guys, Easton here from Newcastle, Australia.


I used to use a powershot S45 (still got it, just using the 300D now), and i'm a total newbie with this whole SLR type thing.

I have an issue with focusing, and someone mentioned to me that my camera body is a dud and that i should get it replaced.

But i'm hoping that it's something that i'm just doing wrong, and not the cameras fault. So thats what i'd like to show you guys first. So heres a sample.

Focus has always been difficult for me to control, especially with such a short DOF (i'm using 50mm F1.8 lenses). But i think this is mostly just to do with me being the D-SLR newbie photographer.

But there is a problem that seems to reoccur every time. I'm talking 95% of the time, this is no exaggeration, so either i'm doing something wrong (which i hope you guys can show me how to avoid it) or there really is something wrong with my camera.

Everytime i take a shot of my car, particularly at this angle (which is most of the time ) it focuses on the front wheel/door area. But it ALWAYS starts to lose focus when it gets closer... which is the front of the car (the most important part that needs to be sharp)

As a result, the front lights is always out of focus. Sometimes the light on our RIGHT is sharp, because thats at a similar distance to the wheel on our LEFT.

But the light on our LEFT IS ALWAYS out of focus. It also happens to be the part of the car that is CLOSEST to me.



Remember, sometimes the lights on our RIGHT is in focus as well. But the LEFT lights (the corner of the car closest to me) is ALWAYS out of focus.

Now i try increasing the F stop, and i bring it up as high as F8 or F11... but instead of extending the DOF to encompass the front of the car... it STILL throws the front of the car out of focus. It only seems to be extending the focus to the BACK of the car.

So basically as i increase the F stop number... the background starts getting sharp, whilst that left corner of the car is still slightly out of focus!!

This is driving me insanely mad!!!!!!



That shot was taken at F11, notice the background now is starting to get sharp as well?

But that left front corner lights is STILL slightly out of focus. The one on OUR RIGHT is fine, but the one on our LEFT (closest to me) is still out of focus... even at F11 with the background starting to look sharp!

So whats wrong? Is it me? Have i not done something right? Is it the camera? Is it the lens?

I tried manual focusing, with very poor results. I'm horrible at manual focusing, besides... AF should be able to do this for me anyway!

And Yes, i point the squares and make it blink a red dot on the FRONT lights of the car, then reframe and press the shutter all the way down. This is still causing this problem on me.

The only time where the front lights of the car is completely in focus, is when i move MUCH closer to the car (Where the front bonnet/body of the car fills up the entire frame), THEN the front lights is perfectly in focus whilst more distant parts become more blurry (nice...)

So it's not that the front of the car is out of the lenses focusing range.. because i can move closer and get it to focus as well.

Having said all that, here are some better pics of my car with the 300D. The difference with these ones is that i have used photoshop to SHARPEN these images, i have sharpened the soft lights particularly in photoshop to try and balance it out. (you can even see some sharpening artifacts on that corner) But i should'nt have to do this! The camera should be able to shoot it all in focus for me.



In this photo, that troublesome corner was SHARP and in Focus. But only in this form of composition.


This shot had a slightly blurry light corner as well. But it's hard to say because the whole car was rather soft and blurry. Taken at ISO 800



I'd appreciate any of your help, i hope you can help me out on my little focusing problem

[xmen1977]

sounds like a rear focusing problem

maybe check with the canon aussie experts

[Zerstorer]

Originally Posted by eyst But the light on our LEFT IS ALWAYS out of focus. It also happens to be the part of the car that is CLOSEST to me.

Quote: The only time where the front lights of the car is completely in focus, is when i move MUCH closer to the car (Where the front bonnet/body of the car fills up the entire frame), THEN the front lights is perfectly in focus whilst more distant parts become more blurry (nice...)

Doesn't sound like a problem.

Depth of field doesn't propagate equally front and back. There will always be greater zone of focus behind the focused pt rather than in front.

This is because depth of field is a function of subject to camera distance as well.

The solution(as you have already discovered) is to always focus somewhere near the closest portion of the subject at all times.(A rough guide for maximising depth of field is to focus on the front 1/3 of the subject field).

[Zerstorer]

Basically, you have just unearthed one of the pitfalls/advantages of an SLR/DSLR vs a smaller format digicam which is the much shorter depth of field.

Perhaps you can work this to your advantage and experiment with selective focusing in your images.

[mpenza]

try the auto-depth of field mode, where the camera will step-down to the right aperture to ensure all the focussing points are in focus.

[sulhan]

Hiee...

Here are my inputs....maybe if you would pen down a physical subject....like this car on paper and sketch the estimated DOF....it can help you select the focus point....



In the diagram the DOF should ideally cover the blowe zone as it encompass the left corner of the back of the car and the right corner of the car....

So if you are by the road side.....you can use the kerb to be a measure of the depth of field ....

Set the camera to manual mode....and estimate the distance you want to be away from the car...change the aperture to various settings and see from the kerb the rough DOF you gonna get if you focus at a particular point....

Then translate this DOF to a spot on the car....in this case....with the given slant position of the car to the camera....you can obviously use the door line to set as the focus point (set to Manual focus.....if possible ...since this car is not moving at all......).


Once its there then take a photo based on this focus point and then stop down or up accordingly to get a variation of DOF......(note that the DOF is not always equal front and back....

SO try this out.....it should work....

regards,
me

[Zerstorer]

A simple rough guide would be to assume that of the total depth of field. 2/3 is distributed behind and 1/3 in front.

Hence you would always want to focus on the subject pts nearer to you.

[StreetShooter]

2 factors are involved here:

1. The AF sensors occupy a larger area than what you see in your little red square, and they are more sensitive to high contrast area. Your car wheels provide a greater contrast than your car lights, so when you think you're locked focus on the car lights, you're actually locked focus on the wheels. Because the 300D viewfinder is dimmer than the 10D's viewfinder (which is already dimmer than a film SLR's viewfinder), you can't really see this, and assume that you're locked focus on the lights.

The reason the problem "disappears" when you're closer to the car is simply because the lights will then occupy a larger portion of the frame, and the AF sensors will lock focus on the lights now, since the wheels are no longer near enough to the AF sensors to confuse them.

2. What Zerstorer said about DOF is correct. There's an excellent and easy to understand writeup here:

http://www.cc.utah.edu/~klm6/3730/depthoffield.pdf

This is extracted from the pdf document:

[eyst]

Wow... thanks for the most FANTASTIC and informative reply guys.

Makes me feel a whole lot better now to know that my 300D dosn't have to be returned!

There are afew nibblies i'm still unsure about, such as umm.

When you hear that "Beep beep" sound, does that mean that it's locked in focus? And that you can recompose the shot and press the shutter all the way down?

I think my problem could be to do with the camera refocusing when i recompose. Though it only seems to do this sometimes and sometimes not (i forget which mode i'm in for what etc).

Like i try to focus on the closest part of the car, but i think when i recompose it refocuses back on the front wheels again.

I try to beat it... by focusing on the front of the car (or subject whatever) then in a really quick split second i recompose and press the shutter down.

Unfortunately, the camera is alot faster at refocusing than i am at doing that.

[mpenza]

if you prefer to recompose, select only the centre focus point, focus and recompose.

[MaGixShOe]

maybe its because of the AI Focus in use?

when u focus on ur front lamp and recompose the focus is shifted again because of the AI Focus in use which tracks subject movement.

if that is the case then u will have to manual focus or maybe other 300D users can help on this

anyway keep the nice car photos coming in!

[loupgarou]

actually I don't seem to have any problems with the AI servo kicking in with focus/recompose technique. I don't use 7 point af though, only select center or bottom. maybe that's it.?

[showtime]

whats happening over here is the effect of hyperfocal distances. there is a focus distance that gives maximum depth of field for a given focal length and apperture... there are charts that compute this...

but generally, without the use of all these troublesome cards and all, the trick should be to set the focus towards the nearest point required to be in focus. this is because of the 1/3 and 2/3 issue that was toked about in earlier posts.

also the nearer you stand to the subject, the shallower the dof for a given focal length and apperture... so all these might contribute to your problems.

[Zplus]

Try this, check if all 7 focus points are active. If it is, any movement (eg the old focus lock - 1/2 press - recompose - shoot routine) would activate the AI servo.

Then try this, scroll through the 7 points and choose the one you wanna focus. Focus and shoot.

OR

Select the center focus point only and use your old focus lock - 1/2 press - recompose - shoot routine. As mpenza has identified....

The last 2 methods does not activate AI servo.

[hong2]

Hi Eyst,
You got very useful advice here provided the camera is working correctly.
Try the above software that came with the package. Check whether the focus pt (shown as a red box when you select the option in menu bar) is sharp. If it is not, sth wrong with the camera. You shouldn't have to spend so much efforts using a wide angle to take the photo of a car. With small f-stop, everything should be sharp. There are quite a few treads discussing focus problems in dpreview. A few people did exchange their cameras. Good luck!