Do I have a faulty 50mm 1.8 II?

[Will James]

Hi,

Took some shots about 20 mins ago of my partner's niece and my cat (below)...for all of them I used the centre focus point, autofocused, recomposed, shot. The 1st and 3rd images did focus correctly, but I'm starting to think my lens is slightly back focusing as you will see on no.2 her shoulder is in focus and not her eye. I focused directly on the bottom of her eyelid to ensure I got it in focus and it has missed it by quite a bit. This hasn't just happened today, it happens quite often and I often have to take at least 3 shots of whatever I'm shooting as I know some will be out of focus for no apparent reason.

Is it me or could I have a faulty lens? Any help on this will be greatly appreciated.

#1 - Left eye in perfect focus.

#2 - Right shoulder in focus rather than eyes....

#3 - Eyes in perfect focus

Will.

 

[The23rdman]

What aperture? If it's anywhere near wide open focus recompose won't work very well.

 

[odd jim]

Impossible to say unless you put the settings up!

Most importantly, what aperture settings you used, as the Canon 50mm f/1.8 can be soft wide open. I dont shoot any wider than f/2.5 with this lens as at f/1.8 to 2.5 the depth of field is too small for most things.

EDIT - beaten to it above!

 

[Will James]

What aperture? If it's anywhere near wide open focus recompose won't work very well.

Impossible to say unless you put the settings up!

Most importantly, what aperture settings you used, as the Canon 50mm f/1.8 can be soft wide open. I dont shoot any wider than f/2.5 with this lens as at f/1.8 to 2.5 the depth of field is too small for most things.

EDIT - beaten to it above!

Ah sorry I meant to put the settings up, I apologise, I usually post via Flickr so forgot about that

All have the following settings: 1/100, f1.8, ISO200.

Having just read another post, I think I've realised that a) I should use AI servo mode (I used one shot), and b) if I want to compose well I have to use a different focus point rather than centre then recompose...

I'm hoping that I haven't got a faulty lens, it's within warranty but it's just hassle having to send it back for repair....

 

[odd jim]

No, its mainly down to the fact you shot at f/1.8.

The Canon 50mm f/1.8 is fairly soft at this focal length and you'll only get a tiny amount of the frame in focus this wide open. Up the ISO to at least 400 and shoot above f/2.5 or 2.8.

One of the reasons I bought the Canon 35mm f/2 was because the 35mm is still sharp even at f/2 which the 50mm isnt.

Oh, dont use AI servo mode unless the subject is significantly moving (I only really use it for sports) especially with the 50mm as its focusing is very slow. Definitely dont use it for portraiture...

 

[Will James]

No, its mainly down to the fact you shot at f/1.8.

The Canon 50mm f/1.8 is fairly soft at this focal length and you'll only get a tiny amount of the frame in focus this wide open. Up the ISO to at least 400 and shoot above f/2.5 or 2.8.

One of the reasons I bought the Canon 35mm f/2 was because the 35mm is still sharp even at f/2 which the 50mm isnt.

Oh, dont use AI servo mode unless the subject is significantly moving (I only really use it for sports) especially with the 50mm as its focusing is very slow. Definitely dont use it for portraiture...

Ok thanks Jim!

Yeah I've only managed to get a handful of 1.8 shots super sharp and I prefer both eyes in focus anyway so should use at least f/2.5.

Yes I've seen results from the 35mm f/2 and it produces stunning results.

Ok I won't use AI Servo, I'll just make sure I use at least 2.5, which still can give excellent results (especially for ~£80!)

Talking of AI Servo, this might be a totally newbie question but if I'm using just the centre focus point on a car going around a race track, for example, the AI Servo mode will only keep focusing on that active focus point, so I have to keep it on the car at all times - is that right?

Thanks for the help

 

[odd jim]

Correct on the AI servo!

The 50mm f/1.8 is a great lens, but really the f/1.8 side of it can only be usefully used for effect, rather than to let more light into the camera for a low light shot which can be very frustrating! But by closing it down to at least f/2.5 and above (and upping the ISO to compensate to keep the shutter speed up) you should get shots which have better overall sharpness!

 

[Will James]

Thanks Jim Great tip

 

[futureal33]

It also depends on the intended use of the photo

f/1.8 can be sharp enough for most things realistically, unless you're printing enormous, and then a bit of post production sharpening should give you the extra bit you'll need.

I was shooting at a party the other week, and f/1.8 was a lifesaver - I was already at ISO 6400, so had little else to play with (no flash).

Experimenting with the focus and shooting wide open (1.8) is a great way to learn. As Dean also said, focus recompose wont really work with this lens, as your focus area is so small that even breathing in/out could affect where the focus falls

HTH

 

[Will James]

It also depends on the intended use of the photo

f/1.8 can be sharp enough for most things realistically, unless you're printing enormous, and then a bit of post production sharpening should give you the extra bit you'll need.

I was shooting at a party the other week, and f/1.8 was a lifesaver - I was already at ISO 6400, so had little else to play with (no flash).

Experimenting with the focus and shooting wide open (1.8) is a great way to learn. As Dean also said, focus recompose wont really work with this lens, as your focus area is so small that even breathing in/out could affect where the focus falls

HTH

Hi Nick,

Thanks for the advice. I see what you mean about it being a lifesaver, I've had a couple of shots that I was on the limit of my ISO and shot at 1.8.

Although I knew the band of focus is tiny at f/1.8, I was naive not to realise that moving slightly would affect the focus by a lot, so I'll bear that in mind too

Just added you on Flickr.

Cheers, Will.

 

[odd jim]

...it also depends on how close the subject is to the lens.

F/1.8 in relation to Will's photos, the subject is large in the frame and opening up the 50m in these circumstances will always end up with bits in focus but a lot oof.

I barely use f/1.8 on this lens, and compared to how the 35mm handles f/2 you can see its shortfalls when wide open.

That said I agree it can be a life saver, and I think thats how it should be used. As effect, or and only if the conditions are that bad you HAVE to use it wide open.

 

[Russ77]

...it also depends on how close the subject is to the lens.

F/1.8 in relation to Will's photos, the subject is large in the frame and opening up the 50m in these circumstances will always end up with bits in focus but a lot oof.

I barely use f/1.8 on this lens, and compared to how the 35mm handles f/2 you can see its shortfalls when wide open.

That said I agree it can be a life saver, and I think thats how it should be used. As effect, or and only if the conditions are that bad you HAVE to use it wide open.

Agreed!!! Saved my bacon at a kiddie (under 12 months) Xmas party where I couldn't use a flash 'cos the ceiling was grey and about a mile high and there was no natural light!!

Think I opened it up to about 2.8/3.5 and got perfectly usable shots.