My Canon 50mm 1.8 is maybe not as sharp as it should be?

[NickStevens]

Hi Guys

Could I get some advice on this ASAP as if it is a faulty lens it can go back to the store today.

I was holding out for a 1.4, but a 1.8 came along today at a good price, so I went ahead and got it.

Used it for the first time tonight, wanted to try and get some serious blurred backgrounds on some karaoke singers, which did kinda work well.

But I was getting a LOT of focused backgrounds and blurred singers in the worst case scenario, and in many somebody standing just 6" behind was blurred, but the person at the front was sharp.
I was also finding that I would focus on the singers face, then they would move forward/back just a couple of inches and blur :x
Now I know about depth of field and I was stopped down to f2.2........I switched to f5.6 and still ended up with some blurred pics and it got kinda annoying (this is my first time out with a fast lens btw)

The lens also dosnt seem razor sharp even when its perfectly focused....

So do I have a faulty one........is it just a crap lenes.......or is it me?

If the lens is ok, and I should be getting better results, I think I have some options:
1) Use a higher apature to give more room for a little movement and or somebody else being slightly off the focal plane.
2) Use a faster shutter speed? (I was using around 1/10, and using second curtain flash to freeze.)

Can anybody offer advice at how best to do this, bearing in mind the light is poor and theirs nightclub lights screwing with the exposure all the time too.

 

[ralphh]

Well the DoF is very thin as you know. If you were in focus and the singer moved out of the DoF before you took the picture, that's clearly not a lens issue.

What i would suggest is testing it on something static first - select the central focus point only and go take a bunch of photos of static objects and see if it really is focusing all over the place.

It's not a particularly fast focusing lens, and in a dark environment with moving subjects, i wouldn't be overly surprised to hear you were having issues.

It also might be worth opening them up in DPP and look at where the active focus points really were; sometimes I'll get an eye out of focus but an eyebrow in forcus with my 85L, and think "grrr, damn stupid camera", bring up the focus point overlay in DPP, and sure enough, focus point is on eyebrow, and all the "but, but, but, I didn't, gaah, all LIES" in the world doesn't change the evidence as to who is at fault :lmao:

I owned one of these very briefly - for about a day until I took it back to the shop and got the f1.4 - I didn't have any focus issues with it, but it wasn't all that sharp and had really really low contrast and was quite hazy. You do get what you pay for, and while it is good for the price, there's only so much good you're going to get at that price. The 1.4 is a big step up and in real terms it's not that much more expensive - ie yes it is 3x the price, but it's only £180 more, which isn't a lot more to spend on a lens if you see what I mean

 

[cgipson1]

Haven't used it personally since I am a Nikon shooter. But it is a $100 (US) lens ($75-80 used)... and if you got price better than that, then the seller probably knew it had issues. There are stories of this lens literally just falling apart, or being pulled apart by just a slight tug. No lens is at it's sharpest wide open.. and a $100 lens probably will be worse than a $350 lens (the 1.4). If you stop down a couple of stops... that may make it more usable for you, but personally I think I would go for the 1.4.

Why were you using second curtain? Were you trying to "drag the shutter" for the background?

 

[chris]

The lens is probably fine but you are trying to shoot in very difficult circumstances.

If you can then use a smaller aperture to give greater depth of field. Check DOF tables and you will see how far you can stop down and still retain a blurred background.

Try manual focussing so that the AF doesn't get confused by background distractions - AF will probably try to focus on an element with the greatest contrast which could be a light or reflection in the background. If you can't see well enough to confirm focus in the viewfinder then go back to basics and estimate the subject distance and set that on the focussing ring, remebering that the smaller the aperture the more latitude you have in setting the distance.

Keep trying - with constantly changing light levels and subject movement just about any camera will struggle to keep up and a high percentage of missed focus/exposure can be expected.

Use flash, bounced off a ceiling or wall if possible - this may kill any effect from stage lighting but it may improve hte focus problems by allowing the use of a smaller aperture.

 

[KenC]

I agree that it probably has more to do with circumstances. I see no discernible difference in sharpness, even at 100% magnification, between this lens any my 100 2.8 (non-L) macro, which is known for being a very sharp lens. I've heard of people occasionally getting a defective lens, so that's possible, but first try what someone suggested earlier and put the camera on a tripod, focus on something not moving, and use an aperture of about f8, just to eliminate all the possible "user error." I don't really use this lens wide open, so can't speak to that, but it should be as sharp as almost anything else you'll find at least from 2.8 or so.

 

[pgriz]

Lots of good advice already given. Picking up on what KenC said, here's a method that can help you figure things out.

In diagnosing lens issues, or focusing issues, the thing to do is to eliminate as many complicating factors as possible. So get the camera on a stationary surface (tripod), aimed at t high-resolution target (classified ads at 6-10 feet would do), under even lighting. Turn off the autofocus, image-stabilization, and all the other doo-dads, and focus manually, using the widest aperture and 10x live-view if you have it. Then take a series of shots with the aperture being progressively closed down 1 stop at a time. This will give you a baseline of what your lens is capable of, under ideal circumstances. Chances are, the sharpest views will be around f/5.6-f/11. Check the edge appearance as well as the center point.

Now, turn on the camera autofocus (don't move the camera yet) and let it find the focus itself, using the center AF point. Each time, manually move the camera focus to the infinity mark, and let the AF then find the focus point. Go through the same series (wide-open to fully closed down). Compare your shots and see if for the same aperture the camera AF shots are the same as the ones where you acquired the focus manually. Chances are, they may be a little different, especially at the wide end. But they should not be greatly different.

You can repeat the same exercise with the lens starting at the closest focusing point. If the images are NOT the same (compared to the AF focus acquired from the infinity starting position), then you may have focusing issues.

Now take the camera off the tripod, engage the image stabilization, and try to shoot the same target from exactly the same position, but now holding the camera. Compare the results handheld, with the ones you've done before in this series.

By going through this process, you can determine if it is the lens, the autofocus, or your technique that is causing the lens not to perform to your expectations.

 

[NickStevens]

Ok well....

I bought the lens second hand from cash converters and got a part trade for a bridge camera I was selling, didn't get close to what it was worth but I guess that's how it is when you take stuff to these places.

I paid £60 for it which I thought was expensive for used but never mind. It suited me coz I got rid of the bridge camera.
I took the lens back today and explained the issue, if in dounght bamboozle them with tech jargon and they just smile and nod, then agree to a refund :-D

So I got my money back, went round the corner to a camera store and bought one brand new for £88.
This one does seem better during initial testing so at least I will know for sure if it was the used lens or its just crap anyway.
If it doesn't please me with the results, I'll put it on eBay and get a 1.4.
Im pretty picky so I have a feeling within a few months I will have a 1.4.

I THINK my biggest issue was ME, I tend to half press the shutter for a while so it's focused then fire the shot..... So at that DOF if me or them moved even a fraction boom non razor sharp piccie.

Yes I do use second curtain so I can drag the shutter, although I wasn't down too low last night.
One thing I hate is photos in nightclubs or discos that look like it's noon on a summer day..... I Think you need to take in the dark, show some disco lighting and pop a little flash onto the subject.
Im still practicing with that but I'm getting much better after watching a number of instructional videos on YouTube.

Thanks for the help guys

 

[NickStevens]

When I said about the half press, I meant...
I will frame the shot then focus, Ill then stay half pressed waiting for the right moment...... Coz people are not posing, I like to catch a smile, or even a glance in my direction lol

MAYBE I should try putting the focus on servo and hope it can keep up with a slight variation in distance and keep it sharp.

 

[o hey tyler]

1. Gets Canon 50/1.8 II used after remarking that one is saving for the 50/1.4 for the better all around quality.
2. Unsatisfied with focusing speed and focus accuracy of a cheap lens
3. Demands money back.
4. Buys same cheap lens with refund money.
5. ???????
6. Profit!

 

[NickStevens]

Nah no profit lol

It should do for now till I can get a 1.4

So should I switch to servo focus yah think, I nearly Always use single shot.