Canon 50 1.8 focus problem?

[elizabeth_l.]

<p>I just got in my new 50 1.8. I've been shooting lots of photos of my son to familiarize myself with the lens. <br>

Unfortunately, a large number of the photos I've taken with this new lens are out of focus. Since I am a newbie, I'm wondering if the problem is me or the lens. I haven't had these same issues with the kit 18-55 lens that came with my Rebel XTi. With the 50 1.8, the photos that are in focus look great. But, there are so many where the camera seems to pick the wrong focal point. For candid/environmental shots of my very busy 2 year old, should I have the camera set on AI Servo, on One-Shot, or AF? <br>

Any recommendations would help. I'm just not sure whether to change what I'm doing or exchange the lens.<br>

Thanks!</p>

[tdigi]

<p>Try using only the center focus point. Focus then recompose. Try to focus on an eye if possible. My guess is the photos are blurry because of the shallow depth of field the lens provides ( assuming your shooting at F2.8 or wider ) <br /> Also check your shutter speed. If your shooting moving kids you will want to keep it pretty fast, maybe around 1/125 or 1/250. <br /> Flash will also help freeze motion.<br>

You can use AI servo or 1 shot depending on what your trying to do. I usually go with 1 shot. </p>

[matt_m__toronto_]

<p>i think you need to understand depth of field a little more. i'm assuming your kit lens is a 3.5-4.5 (ish?)<br>

even on a full frame camera where the 50mm is a true 50mm, the depth of field at 1.8 when shooting at close distances is very minimal. with your crop camera, this lens is more like an 80/85mm lens...and at close distances, and 1.8 the dof will be razor thin.</p>

[nathan_meador]

<p>Can you post an example, along with what mode you are shooting in, or at least the aperture/shutter info? I think it may very well be a DOF issue. </p>

[mathew_gardella]

<p>it could also be the lens... i have the same lens and mine bumps back and forth in and out of focus even when using a single focal point, even when using an aperture greater than 4.0... it does however, seem to perform better in bright lighting when it does not have to hunt... the problem is even less on my 40D (better low light performance that the 350D i think) i imagine this lens would work best on the 5D full framer.... perhaps that's why i bought the sigma 30mm f/1.4... works like a charm on the 1.6x.... i suggest you try it in better lighting conditions... regards..<br>

mat</p>

[PuppyDigs]

<p>Like others have said, you need to pick the AF point, not the camera. How the heck does a camera know what you want to be in of focus? It tries to guess and tends to pick the brightest object, often a prominent object behind your subject. With that said, the 50 1.8 is poor in low light and often misses (racks back & forth) even if you choose the correct AF point. In such cases you need to focus on a strong point of contrast or use MF.</p>

[elizabeth_l.]

<p>I am very new at this, but I want to learn. Sounds like I need to learn more about shooting at low apertures. <br>

Here are a few examples. To correct the problem, should I manually focus every time, or choose AF points for every shot? Since I can't seem to get him to stay in one place, I'm worried I'd miss shots doing either one. Any advice?</p>

[elizabeth_l.]

<p>The above photo (very out of focus) was 2.0 1/800 ISO 100, portrait mode.</p>

[elizabeth_l.]

<p>This one was 2.0 1/1000 portrait mode, ISO 100:</p>

[bryantan]

<p>Manually select a focus point each time. Shouldn't be too hard once you get used to it. With practice, it shouldn't take much longer than a full second. After all, you only have what, 7 or 9 focus points to worry about?<br /><br />If it's too complicated, get a 40D or another camera that has a one-button AF selection mode.</p>

[thomas_hardy1]

<p>It looks like the focus is in front of the little boy in the first shot. A right focus point was probably used. You might have more success by using the center point and then recomposing if you want off center shots. </p>

<p>My daughter just finished a photography class and learned to use those 50mm lenses in manual mode. You will always know what you have focused on that way. The down side is the very small focusing ring.</p>

[matt_m__toronto_]

<p>YES to manual focus, especialy when wide open and close</p>

[i._l.]

<p>For your 1st shot, if you use center point AF, autofocus on the boy, do NOT recompose, take a picutre. Result should be better.</p>

[matthijs]

<p>Manual focus on a 50/1.8 is pretty bad / hard to do. But using center point AF and reframing the shot is pretty easy. (Though for Macro like shots this might take your subject out of the sharp area.)</p>

[tomsphotography1664882219]

<p>I have just bought my first ef 50mm 1.8 on a 40D and i am loving the DOF .... but you must get the focus point spot on or it is wasted. In both your shots there is a tack sharp point, in the first one it is in the stone and weeds just in fornt of the subject and in the second it is on the boys t-shirt at the point where the v neck opening sticks out indicating again that your point of focus was forward.<br>

your cure is easy, lots of practice. The slightest movement in your subject either by the them moving or you and the pic will seem out of focus but if you look closely you will see the focal point will be there somewhere just not where you want it.<br>

It is a great lens once mastered.</p>

[chengxian_zhou]

<p>Hi<br>

This lens is cheaper. Made by plastic material. Lots peple complain about focus and sharpness. I spent extra $60.00 for readjustment. Now it is sharper and focus stablely and as my master lens.</p>

[peter_wang6]

<blockquote>

<p>I am very new at this, but I want to learn. Sounds like I need to learn more about shooting at low apertures. <br />Here are a few examples. To correct the problem, should I manually focus every time, or choose AF points for every shot? Since I can't seem to get him to stay in one place, I'm worried I'd miss shots doing either one. Any advice?<br>

This one was 2.0 1/1000 portrait mode, ISO 100:</p>

</blockquote>

<p>The example you provide is in perfect focus....on the plants growing on the rock. The good news is it's not your lens, it's how you're shooting.</p>

<p>I'm not familiar with the Rebel XTi but on my 5DmkII, when I shoot in RAW mode, I can open up the images in DPP and see the AF point(s) that were used to judge focus.</p>

<p>Something that those who have advised to use only the center AF point have not mentioned, however, is that you must select a spot that contains enough contrast for the AF system to work. This can be difficult if the subject you want to be in focus has low contrast or few distinguishing features. Using the entire set of AF points often results in more accurate focusing under most circumstances...except in your situation, where the camera has judgmentally selected a spot in your scene that you did not intend to focus on, and the DOF is extremely shallow @ f/2.0.</p>

<p>To correct this problem, you have two choices: (1) use the center AF point, or (2) use manual focus. The first option simply requires you to place the center AF point over the desired subject, lock focus, then recompose as desired before fully depressing the shutter button. This works in many instances, but may not be sufficiently accurate for macro work. The second potion is very tricky and only recommended if you have enough DOF. One way to gain some accuracy is to adjust focus around the range of the subject distance, observing the near and far points where the subject appears to just lose focus. Then take the midpoint of these two distances as your chosen focus. However, at very wide apertures and/or close subject distances, even such a method is unlikely to provide the desired focus.</p>

<p>Finally, if you have reason to believe that your lens has a focusing problem, shoot a few test charts and try to determine if its behavior is within spec.</p>