Possible problem with 50mm lens?

[Mike Dunning]

Howdy folks - I hope this is the right forum to post this in.

I've recently purchased a D70s along with a few other goodies including a Nikor 50mm 1.4D AF lens. I'm having trouble with a lot of pictures turning out somewhat blurry. What looks to be perfectly in focus in the viewfinder is not turning out that way once I get it in to the computer. I've tried adjusting the viewfinder diopter, but images still seem a tad bit out of focus.

I've noticed that this mostly occurs when I'm taking low light shots with an aperature of 1.4... such as taking pictures of a band. If I were to frame up, say, someone dancing, I'd focus on them and snap the picture. Once I got back to PP, I'd notice that the zone of focus is usually behind the subject that was (supposed) to be in focus.

Am I missing something? Or does this lens not perform optimally at a wide open aperature in low light? Has anyone else come across this?

Thanks!

[Alex]

Mike,

Are you using the centre focusing point and not one of the side ones? If you are sure that it is the centre point and you are directing it at a subject point you want in focus and that doesn't happen then it sounds like front focus. If this only happens with this particular lens then the lens may need to be calibrated, serviced by Nikon. Make sure first that you focus pricesly on a certain point, because with f1.4 everything but the focus point SHOULD be out of focus due to a very shallow DOF.

Alex

[wendellt]

you either have a backfocussing issue with the camera
or you may not be aware that fully wide open at f1.4 produces a slightly blurry image

[gstark]

you either have a backfocussing issue with the camera
or you may not be aware that fully wide open at f1.4 produces a slightly blurry image

Wendell,

No it doesn't.

But the depth of field is very shallow, and this may appear to be a focussing problem.

Mike, I would suggest that this is probably what is happening with you, and what you're seeing is simply an issue related to the very shallow DoF that you'll see at with this lens wide open.

As a basis of comparison, what happens when you make images, using the same lens, at, say, f/5.6, /8 or /11? How do they look?

Could you perhaps post some samples?

Thanx.

[Oscar]

Hi Mike, I'm no expert here - but a couple of questions which may help with this issue - what focus mode are you using? and does the in focus light appear in the view finder?
Have you had a look in the manual in regard to focus. If you are using AF-C or AF-S you can select a focus area and perhaps you have this set to the wrong position (I had this problem occur when I started to explore the settings and didn't really know what I was doing - still happens a lot).
You could also try a few test shots in the day and modify the settings to suit. Hopefully there isn't a problem with your camera or lens - are they under warranty? Cheers, Mick

[shakey]

Also what is the shutter speed? Someone dancing may have motion blurr (which could simulate incorrect focus) if you are using too slow a shutter speed. Presume you are using AP (set at 1.4) but if you have the ISO set to 200 then you will still likely have a low shutter speed if the lighting is poor

[Mike Dunning]

Thanks for all of the replies! I should have stated that all of the pictures have been manually focused. I realize the f/1.4 will give a very shallow depth of field - its one of the main reasons I bought the lens.

@gstark - I haven't shot enough at f/5.6, f/8, etc, to notice. But now that you mention it, I'll give it a shot. So far, its mainly been at f/1.4 in low light conditions.

@Oscar - I am using manual focus. The focus area is set to Single Area (and the bracket in the icon is centered as well.) The in-focus light does appear in the lower left corner of the viewfinder when it "thinks" an image is in focus. On a side note, when I first got the camera, I had somehow switched the focus area to the left bracket, and for the life of me couldn't figure out why the auto focus had a hell of a time focusing on my subjects!

@shakey - I've been shooting mostly AP set to 1.4. On the following four images, two of them had a shutter speed of 1/250 while the other two were 1/25. The two at 1/25 (the colorful images of the guitar players) are nearly identical in composition and distance from the camera. You can see the motion blur on their fingers as they changed chords, but their bodies as a whole should have remained more or less in focus as they were not moving. The major difference between the two images, aside from the obvious focus issue, are the colors of the stage lights. These photos were shot at ISO-800 rating (the stage lighting wasn't exactly ideal...)

Excuse the subjects in the first two images - crazy women under the influence of alcohol and good music. Chosen because they illustrate my problem exactly.

Thanks for any advice or tips!

[Justin]

Hi - I've done a fair amount of low light shooting recently and what i see here is similiar to what I get - to the point where I thought I had focussing problems with the camera and ran some focus tests, which proved that it was the operator .

Couple of questions
- have you set the diopter back to neutral?
- in low light it is extremely difficult to get your focus, because of the light something can look in focus to your eye but it's not.
- the green light just ain't that reliable - sometimes you just have to shake your head - there was another post here recently that noted it could be up to 43% out of whack or some-such.

Suggest you run some focus tests - I found the chart at Tim Jackson's site easy to use -

http://www.focustestchart.com/chart.html

[shakey]

Of the "very friendly girls" series, there is a huge focus difference between the two shots. There is very little time difference between the two shots, so you must have changed focus between the two. The second one is reasonably sharp

With the band shots ... 1/25 handheld on 50 mm lens on a D70 with a moving subject is no way to judge focus....now if you were photographing a bass player that would be different...they are basically inaminate objects...I thought the short guy might be playing bass but he seems to have 5 strings on his instrument...maybe he's a very smart bass player..

Basically you cannot rush to judgement about "backfocus" in the environment you took these photos. You need a much more controlled test situation.

Finally I find it very hard to manually focus using the supplied focus screen and the green light. I just bought a Katzeye focussing screen to try and overcome this problem.

[PiroStitch]

i don't see any issue with the pics you've taken aside from the obvious OOF shot in the first pic. The rest seem normal for low shutter speed and wide open aperture.

[seeto.centric]

hehe i thought the guitarist on the left was a bass player at first too.. but the strings look like bass strings. never seen a 5 string bass before but!

at ISO800 and f1.4, the lighting mustve been REALLY bad to only get 1/25....

-julz

[moggy]

hehe i thought the guitarist on the left was a bass player at first too.. but the strings look like bass strings. never seen a 5 string bass before but!
-julz

Five string bass guitars are quite common.