Miss focsing through viewfinder but work in live view

Steven001

Steven001

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Hi folks,

I noticed the other day I was getting poor results with my Tamron 17-50 (non VC). I tested it today and whilst using auto focus (centre focus point) through the view finder, every photo was soft and looked OOF, but when I used auto focus in live view mode the photos were sharp and as expected.

Is this likely down to the camera rather than the lens? Is there any way to sort it?

I'm using a D7100.

Thanks
 
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When you use auto focus in live view the images are soft?

When you use auto focus in love view the images were sharp?

I must be missing something here....
 
Live view uses contrast detect to auto focus and the viewfinder uses phase detect. 2 separate systems. Contrast detect is always spot on (at least all of the ones I've used are!) albeit usually quite slow. PD is faster but has tolerances it works within. The same goes for the lens. Sounds like you may need to fine tune the af (viewfinder af or PD) which the D7100 does do. There are various methods from using software like reikan focal, to focus targets like spyder lenscal and even using a ruler and a box of cornflakes. Also look up the dot tune method on youtube.
 
When you use the viewfinder the camera uses Phase detection.
When you use live view it uses contras detection, which is slower but far more accurate.
Phase detection is far faster but inherently inaccurate and needs to be set up very carefully, and often needs to be adjusted for each lens.
I do not know if the D7100 has this facility for individual lenses.
 
Thanks guys, I have bought a cheap cardboard calibration card from eBay to see how accurate the focus is. Does the fine tuning setting effect the live view auto focus also?

Would it be best to test the lens at 17mm, 50mm or both?

Thanks.
 
Steven001 said:
Thanks guys, I have bought a cheap cardboard calibration card from eBay to see how accurate the focus is. Does the fine tuning setting effect the live view auto focus also?

Would it be best to test the lens at 17mm, 50mm or both?

Thanks.
Click to expand...
With Nikon you can only do one focal length per lens so I'd do it at 50 as DoF will cover you more @ 17mm than 50mm. It won't have any effect on live view AF.
 
Steven001 said:
Thanks guys, I have bought a cheap cardboard calibration card from eBay to see how accurate the focus is. Does the fine tuning setting effect the live view auto focus also?

Would it be best to test the lens at 17mm, 50mm or both?

Thanks.
Click to expand...
Fine tune doesn't affect live view. In fact if you are in live view and go to the fine tune option it will be greyed out.

I always fine tune to the long end as this is where focus errors will be more apparent due to the shallower DOF. I do wish Nikon would pull their finger out of their arses and allow fine tune at both ends of the zoom like Canon, Sigma and now even Tamron allow you to do.
 
Steven001 said:
That's great thanks guys. This is what I bought if anyone else is interested: http://www.ebay.co.uk/itm/371721558179 dirt cheap and get really good reviews on Amazon.

Is there an optimal distance between the calibration card and the camera to get the best result?
Click to expand...
Not really, you will read a lot of conflicting info. It's not full proof as fine tune can vary between different distances.
 
Focus errors occur for two main reasons. The positioning of the sensor and the focus receptor are not accurately positioned in relation to each other.
and secondly that the lens focus mechanism does not come to rest consistently.

These problems do no exist on fuji x cameras, as the phase detection pixels are part of the same sensor as the contrast detection pixels.
The latest versions are very close to the speed of the best professional Dslr's. and rather faster and more accurate than second level Dslr's.
the remaining problem is the slight viewfinder lag on some versions.
 
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