FOCUS PROBLEM

[Luca Nervegna]

I posted this thread on general forum but here is better :hurray:

I'd like to understand this problem with focus..

between the face out of focus near the camera and the background out of focus as well, there's a strange effect ..

i don't think is the lens because it happend in tests as well, and i tryed different sets..

this effect comes up just with the skin and not with other object, and just with a background out of focus..
when the girl in focus passes rear the face out of focus the effects disappear..

sorry for my english.. hope someone understand my mind

any ideas??
thank you

 

[Adrian T.]

That's the lens.

See this post:
http://www.reduser.net/forum/showpost.php?p=421405&postcount=144

 

[Mitch Gross]

It is refraction of light. Hold your finger up close to your eye with a bright background and you will see something similar.

 

[Luca Nervegna]

i know refraction of light.. it's not sot so eavy..
i did tests with zeiss 1.3 and zeiss ultra prime and this effect is present..

 

[Graeme Nattress]

Diffraction or refraction?

Graeme

 

[Adrian T.]

Diffraction or refraction?

Graeme

I think Mitch means diffraction. :smiley:

Refraction can also be a problem - within the lens that is. But since refraction is wavelength dependent, we usually see color fringing (chromatic aberration). And this is not the case here.

 

[Luca Nervegna]

i saw the same aberration tonight at the cine in a movie..
is it possible that it happens easily at open iris?

 

[Mitch Gross]

Yes sorry, diffraction.

Hold your finger up really close to your eye and focus on somthing contrasty in the far distance. Move your finger edge past the contrasty point and you will see something similar to this effect. Diffraction of light.

 

[Pawel Achtel]

Yes sorry, diffraction.

Hold your finger up really close to your eye and focus on somthing contrasty in the far distance. Move your finger edge past the contrasty point and you will see something similar to this effect. Diffraction of light.

Ooops, I think I just poked my eye...

 

[Mitch Gross]

You THINK you poked your eye? ;-)

 

[ericyoung]

That's funny Pawel & Mitch! :smile:

 

[ericyoung]

i saw the same aberration tonight at the cine in a movie..
is it possible that it happens easily at open iris?

I think it's just more obvious against a blurred contrasty background - which is more likely with an open iris.

 

[Pawel Achtel]

You THINK you poked your eye? ;-)

either that or it is diffraction :blink:

 

[Luca Nervegna]

I think it's just more obvious against a blurred contrasty background - which is more likely with an open iris.

yes i guess me too..

thank you

 

[Thomas Wright]

doesn't diffraction give rise to refraction? light's bending and interfering innit.