Focussing with a Nikkor 50mm f1.4D

[fyonn]

Hiya folks,

I was recently given a new (to me, but second hand) lens, a nikon 50mm f1.4D. I took it on holiday last week along with my 18-200 lens. I guess I used the zoom for most of my time in the states due to it's flexibility, but I did put the 50mm on several times when I knew light would be low.

one example is when I went to monterey aquarium. aquariums are almost always low on light and I thought it would be an ideal place to use the f1.4 but I seemed to be having a lot of trouble getting proper focus. I know it's supposed to be difficult to get proper focus at F1.4 but still, I was really struggling.

to give some context, I had the 50mm lens on my D300, I'd set auto ISO on (figuring it's better to have a noisy picture than a blurry one), set to increase ISO at a minimum shutter speed of about 1/60 and a max ISO of 6400. sometimes I set the shutter speed higher just in case that was the problem. I tried various different focus modes including auto area and single point AF. it was all hand-held shooting and no flash.

Not sure here if it's down to me or what, but looking at the screen on the back of the camera at the time and on screen now, sometimes it feels like nothing in the shot is in focus.

some of my pictures came out sharper than others (though none looked truely sharp), but sometimes I just couldn't get the fishes in focus, even when they were barely moving. the shutter speeds should have been enough to get a sharp picture.

so what am I doing wrong? is it that hard to shoot in aquariums, have I done something stupid? or could there be an issue with the lens?

I've got some example pictures, I'll link to an external website so you can see the fullsize files. they should have all the exif data intact too.

here is one fish[1] that had the good graces to stay in one spot so I could take a series of pictures at different apertures.

F1.4
F2
F2.8
F4
F7.1
F11

the smaller apertures are clearly sharper than the wide open ones, but are they sharp enough?

two of the better pictures are:

Blue fish at F4
Seahorse at F4

so, what do you guys think?

cheers
dave


[1] I think it looks like an otocinclus?

 

[Nod]

I'm guessing that you had AF set to S (single shot) and that you may have swayed a little forward or backward between achieving focus and taking the shot (easy to do). DoF is pretty shallow at that sort of distance (again, I'm guessing at about 1 metre, if not closer) and large apertures and you may have just swayed far enough.

I've found shooting in aquariums frustrating (shooting fish in a barrel?!) so now tend to leave the camera in the bag unless the place is almost deserted and I can get right up to the glass and steady myself against it. I also use a rubber hood to exclude any stray light and reduce the chance of reflections off the glass. Not yet tried with the D700 and cranked up ISO - maybe next year I can persuade my wife that the CretAquarium will be enough different for another visit...

 

[fyonn]

I'm guessing that you had AF set to S (single shot) and that you may have swayed a little forward or backward between achieving focus and taking the shot (easy to do). DoF is pretty shallow at that sort of distance (again, I'm guessing at about 1 metre, if not closer) and large apertures and you may have just swayed far enough.

yeah, I guess that's quite possible. I didn't think I did but I could easily have done so I suppose. so setting the focussing to AF-C would be better in such a situation you think?

were the 2 better pictures good enough?

I also use a rubber hood to exclude any stray light and reduce the chance of reflections off the glass.

ooh, that's a good idea...

dave

 

[singlespeed]

but sometimes I just couldn't get the fishes in focus, even when they were barely moving. the shutter speeds should have been enough to get a sharp picture.

Theres some trails from bubbles or something floating about ( have a look to the left/above left of the main fish of the f4 picture). Being as these trails extend to 20 - 25 pixels, was the shutter speed realy high enough when any movement is so close to the camera The relative movement across the frame and through the shallow dof could well have combined to give the blurred shots.

 

[fyonn]

Theres some trails from bubbles or something floating about ( have a look to the left/above left of the main fish of the f4 picture). Being as these trails extend to 20 - 25 pixels, was the shutter speed realy high enough when any movement is so close to the camera The relative movement across the frame and through the shallow dof could well have combined to give the blurred shots.

I can see some little white spots.

the shutter speed was 1/80 (the pic's got the full exif info in it, or should do) so that ought to have been fast enough for a 50mm lens shouldn't it? is one supposed to match the real focal length or the equivalent DX focal length? the shutter speed was higher than both anyways.

or should the shutter speed have been higher?

dave

 

[fyonn]

okay,

I've done some more photo's with the 50mm, this time in daylight and not of dark, fast moving fish. Now I've got pics of flowers in the, well I'd like to say garden, but I mean car park behind my flat

Anyways, from the same position I took pictures at all the full aperture stops. links to the full size pics below:

F1.4
F2
F2.8
F4
F5.6
F8
F11
F16

I still think the wider open pictures seem out of focus. I looked up the depth of field for this lens, aperture and subject distance, and it's supposed to be about 2.1cm which should encompass the entire flower head I think.

the shutter speed for the F1.4 picture is 1/8000 so it shouldn't be down to any movement on my part or that of the flower. I had the focus set to single point (with spot over the flower head) and AF-C.

am I doing anything wrong or is the lens just soft when wider open? or does the lens need some calibration?

many thanks

dave

 

[Moos3h]

It is very often the case that these lenses are at their best stopped down a bit. At f4, you still have very little DoF, but it's looking pretty sharp for the parts that are within that limit.

I think you are partly discovering exactly how shallow f1.4 is!

Cheers,
James

 

[fyonn]

I think you are partly discovering exactly how shallow f1.4 is!

But according to 2 DoF calculators, the DoF for a 50mm lens on a 1.5x DSLR at about a meter subject distance is just over 2cm. that should be most of the plant head.

it feels like I can use my 85mm at f1.8 or my 300mm at f4 and get very sharp results, but the 50mm at F1.4, which ought to have a greater depth of field than both the other primes just seems very soft at anything up to F2.8 nearly.

or am I just beating a dead horse here?

dave