Autofocus problem!?

Gaccho · Mar 28, 2011

Greetings.

I have NIKON D300S Camera with Sigma 8mm 1:3.5 EX DG FISHEYE lens. No matter what settings I try, all pictures seems a bit out of focus (infinite focus as well). Does somebody has some advise/tricks to fix that?

PhotoWrangler · Mar 28, 2011

Put it on the little green box. :sexywink:

Without an example, its a little hard to tell you the issue, or give you advice. It could be any number of things... aperture, shutter speed, it may be backfocusing.... really anything.

Big Mike · Mar 28, 2011

It's certainly possible that either the lens or the camera is in need of calibration....but as mentioned, showing us an example should help.

Gaccho · Mar 28, 2011

I see. Ok, here is an example: http://db.tt/qnE2Sfj - be aware it's 20MB!

Here I have used F11 / 1600 sh. speed. Have a look.

Math5 · Mar 28, 2011

I have a D300 and always feel that my shots are just not sharp enough. I'm using nikon lenses, 18-55 18-105 and 70-300. I accept the calibration reply but, would all three lenses be equally uncalibrated? I have put it down to my eyes now, but I'm going to be very interested in this thread. One thing I did find is that I get sharper images by switching off the VR, which may seem strange but, it did marginally improved the sharpness!

PhotoWrangler · Mar 28, 2011

Math5 said:
I have a D300 and always feel that my shots are just not sharp enough. I'm using nikon lenses, 18-55 18-105 and 70-300. I accept the calibration reply but, would all three lenses be equally uncalibrated? I have put it down to my eyes now, but I'm going to be very interested in this thread. One thing I did find is that I get sharper images by switching off the VR, which may seem strange but, it did marginally improved the sharpness!

All three of your lenses are considered 'consumer' grade, so to speak. They will never be as sharp as the 'pro' level glass.

And if I am not mistaken, doesn't the D300/s have the fine tuning adjustment abilities for your focus? Perhaps it needs to be adjusted.

KmH · Mar 28, 2011

Sorry, I got impatient waiting for the huge photo to load, and moved on.

You may find it helpful to look at How Do I Use My Digital SLR? - How to Get Sharply Focused Images

djacobox372 · Mar 28, 2011

That photo is about what I would expect out of a 8mm sigma fisheye on a crop sensor camera--resolution would likely appear better on full-frame.

Ultra wide angle lenses are trying to bend a lot of light towards your sensor, making sharpness a real challenge for lens designers. If this was a 8mm fisheye designed for crop bodies, it might perform better, but it's an 8mm full-frame fisheye which is EXTREME.

There's a reason why the ancient nikon manual focus fisheye cost $2000 used, and the sigma cost only around $400 used. Just look at the difference in the front element size, the sigma is obviously taking some short cuts:

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djacobox372 · Mar 28, 2011

The DOF of an 8mm lens at f11 is almost infinite. I doubt it's a focus problem.

Joves · Mar 28, 2011

Eaxacty!
Yes the D300 series have the focus adjustment for lenses but, I find too many people are adjusting them when they dont need it. They are using bad targets to even do the adjustments as well, so they only make it worse. The lenses you list can vary from copy to copy at startingbe good from f/6 or f/8 through up to f/16 then degrading on the other end. The way to check for front or back focus is to set a graduated measure at a 45° angle and pick a center point. The bad focus will show up easily that way. There are also calibrator tools out there but, you can do the same at home far cheaper if you are meticulous. Also here is a nice sobering little blog on it as well. This Lens is Soft. « Canon Rumors it is about softness but equally applies here. Unless you buy the upper line of glass with any manufacturer you will always have issues.

kashar · Mar 28, 2011

This problem use to happen on older firmware or faulty lense, have you work out of it ?

Garbz · Mar 29, 2011

You call that out of focus? Try not zooming in on the picture and actually looking at ... the picture. When you're pushing that many megapixels down a small opening and then zooming right in trying to identify individual pixels on one of the cheapest lenses you can buy ... you can see where I'm going with this.