Focus problems on Ultra Wide Angle

gwocni

gwocni

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Hi Guys

I have just acquired a Tokina 116 UWA. It is supposed to be the dog's danglies but.........

I think there may be a soft focus problem with the lens. I would like to know a couple of things if possible.

i. In this type of lens is there a focal distance say between 10 & 20 feet, beyond which the subject of focus is too far away to be in sharp focus?

ii. It is said that there is a "sweet spot" with this lens at f5.6 (which seems reasonable to me) but I find that even stopped down to f9 or smaller that there is still a soft focus behind (near) the subject getting softer the further away it goes. Is this normal?

iii. What would the best way to prove/disprove this e.g. what set of reference shots could I easily set up and take to best show up any focus problem?

Probably as clear as mud but I know what I mean :) Maybe UWA have soft focus in the distance when stopped down, I just don't know. Any answers appreciated.

Thanks in advance
David.
 
What body are you using it on? I tend to Manual Focus on mine at night a lot and have it open at f/9.0 and no issues with sharpness throughout the picture.

Have a look at the stuff I have shot with it over here.
 
gwocni said:
Hi Guys

I have just acquired a Tokina 116 UWA. It is supposed to be the dog's danglies but.........

I think there may be a soft focus problem with the lens. I would like to know a couple of things if possible.

i. In this type of lens is there a focal distance say between 10 & 20 feet, beyond which the subject of focus is too far away to be in sharp focus?
Click to expand...


No, all modern lenses should be able to focus to infinity unless you have thing like extension tubes behind them.

gwocni said:
ii. It is said that there is a "sweet spot" with this lens at f5.6 (which seems reasonable to me) but I find that even stopped down to f9 or smaller that there is still a soft focus behind (near) the subject getting softer the further away it goes. Is this normal?
Click to expand...

This sounds like your lens isn't stepping down the apperture and so anything behind the focus point is OOF - however I think this would be obvious if changing your shutter speed resulted in over/underexposure because the apperture wouldn't alter



gwocni said:
iii. What would the best way to prove/disprove this e.g. what set of reference shots could I easily set up and take to best show up any focus problem?

Probably as clear as mud but I know what I mean :) Maybe UWA have soft focus in the distance when stopped down, I just don't know. Any answers appreciated.

Thanks in advance
David.
Click to expand...

How much further back are we talking? 1 foot, 10 foot? It all depends upon how far away you are focusing and what aperture you are using as to whether this is really a problem.

Try messing around near the hyperfocal distance and see if you still have any softness, it should make everything from about 6 feet away to infinity sharp if you've stepped down to about f11
 
Thanks for the replies,

The lens was on a D200. I do have some shots but they are not from the same focus point, angle etc so are not really good as reference points. I will try to get some shots from the same spot at varying distance/aperture etc in the near future.
Thanks for the comments Rick and I did think it should be sharp too but we'll see. If I haven't dumped the original test shots I'll review them as iirc there were differences in exposure!

Thanks again
David.
 
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