50 Mm 1.4 Lens Focus Problem.

[Tibbiemax71]

I took some pics of a friends Bull Terrier at a show today, this is how it came out, obviously the dog is not sharp but if you zoom in and go to the very bottom edge of the pics, the grass is very sharp, which is probably about 6 inches this side of the dog toward the camera. I had the middle focus point selected, the focus point is just in front of the flank on the dogs last few ribs. It was taken on a Canon 50 D, f/ 2, Shutter 1/4000 sec, AF mode was AI Servo.

Have I done something wrong? I am finding this is happening a bit with this lens, don't get any probs with my 18 - 200 mm lense, I did some googleing and some said it has a "front focus" problem? If I bump the f/stop up I find its fine to, but I was trying to get nice bokeh today and its annoying as it could be very sharp at f/2 if it was focusing where it says it is.

[kyliestar]

I took some pics of a friends Bull Terrier at a show today, this is how it came out, obviously the dog is not sharp but if you zoom in and go to the very bottom edge of the pics, the grass is very sharp, which is probably about 6 inches this side of the dog toward the camera. I had the middle focus point selected, the focus point is just in front of the flank on the dogs last few ribs. It was taken on a Canon 50 D, f/ 2, Shutter 1/4000 sec, AF mode was AI Servo.

Have I done something wrong? I am finding this is happening a bit with this lens, don't get any probs with my 18 - 200 mm lense, I did some googleing and some said it has a "front focus" problem? If I bump the f/stop up I find its fine to, but I was trying to get nice bokeh today and its annoying as it could be very sharp at f/2 if it was focusing where it says it is.

adjust your aperture until the dog is crisp, if you have it set to auto focus it won't always work out the way you want it

[kja]

Your lens may front focus slightly. It's common enough that Canon built in a feature on the newer models to fix it.

Download a focus test strip (google it as i don't have the link right now) and set the test up as per the instructions. See what your results are.

If you are finding front or back focus and your camera has a micro adjust feature, follow the directions in your manual to dial the lens in.

If your body does not have this feature, send body and lens in to Canon for calibration.

If the test shows your lens is spot on, then it's a technique issue.

I don't know how you would have consistently gotten the eye in focus with the middle point selected and f2 here - better to move your point to the outer corner as focus and recompose with a shallow depth of field is very hit or miss.

Edited November 27, 2010 by kja

[Tibbiemax71]

Thanks guys. Will do that now KJA, yes I realised that I should have set the focus point off the left, on the eye, or course I realize this after I got home from taking pics Will find the test strip now.

[kja]

Thanks guys. Will do that now KJA, yes I realised that I should have set the focus point off the left, on the eye, or course I realize this after I got home from taking pics

Happens to everyone - and usually on those frames that you really really want LOL

[kja]

Any results yet?

[Tibbiemax71]

Hi kja, I found the test stip thing and printed it out, have been at shows all weekend so haven't had a chance to try it yet, but will hopefully do it in the next couple of days, thanks heaps for your help

[kja]

Sorry, i know I'm too impatient LOL

[Tibbiemax71]

[Tibbiemax71]

OK, I finally got the chance to do this the other day, I think I got the angle of the camera to paper right (45 degrees) from what I can tell, it is focusing as it should be, so I must be the problem, I wonder what I did wrong though Maybe I just need to use it more, the more I practise with it the better results I will get I guess.

[Kirislin]

I notice you used AI servo when you took the pic of the dog. Since he was standing still you might have been better with using one shot to lock on focus. Dont be too disheartened just yet.

[Tibbiemax71]

I notice you used AI servo when you took the pic of the dog. Since he was standing still you might have been better with using one shot to lock on focus. Dont be too disheartened just yet.

Thanks Kirislin, AI Servo is for moving subjects isnt it? I normaly leave my camera on that, so will make sure I change it to the One Shot instead Think I had on one shot for the focus test thing, will have to check.

[kja]

Practice practice practice.

And remember to take more than one frame if you are shooting wide open or almost wide open. That depth of field is a biatch. Check out this Depth of Field calculator - it's a little shocking when you do the math

Just keep at it - you'll get there. And not every shot has to be shot wide open, stopping down a bit can still give you the nice isolation but make your life easier.

[Ashanali]

Yep, take it off AI servo and shoot at about 5.6. It will make a big difference.

[Tibbiemax71]

Thanks guys!! I will do that for sure, I have to get out there more with this lens, like you said, practice!

[Mason_Gibbs]

I got a 50mm 1.8 and I also battle with the focus, need more practice!!

[Tibbiemax71]

I got a 50mm 1.8 and I also battle with the focus, need more practice!!

They are a bugger arnt they!! I go to use mine then think, nah will go with my 18 - 200mm just in case I stuff it up, but I really need to get the 50mm out more and have a go with it.

[Ashanali]

Lots of lenses don't work as well at their extremes and this is particularly so of the 50mm (1.4 and 1.8)

Personally, I try and avoid shooting my 1.4 lens at less than 2.2 if I can help it. It just isn't as sharp as I like when I'm shooting wide open. I've seen many people say the things on various forums so it isn't just my own observations.

[huga]

I know someone with a 50mm 1.4 that feels she always has to use it at 1.4. Then asks why her photos are out of focus. Drives me nuts. If you can use it that wide open, then good on you, but it's way too challenging for me :p

With practice, you will find your favourite range. Mine is 2.2 - 2.8. I very rarely use it out of that range, unless I have the flash on.

[Tibbiemax71]

I have taken some this morning of my kids, I had it on F/2.8 and One Shot, they look ok on the camera so will see what they look like on the puter in a mini when I upload them.