[Guest]

Hello,

there are now Adapters for EF-lenses available with built-in aperture:

http://www.dl-kipon.com/en/articledetail.asp?id=30

http://www.43rumors.com/new-canon-eos-to-micro-four-thirds-adapter-with-built-in-aperture-control/



So, a question for the optics-specialists:

As I assume, the position of the aperture blades in the lens ist important for the IQ.

What do you think?

Is the IQ degraded if you close this aperture within the adapter?



Thanks

Lars

[popo]

Definitely interesting, but not enough to make me want one to play with at that price.



I know the back end of the lens is very different from the front, but I have played with shaped bokeh by selectively blocking the front to interesting effect. On the back, I think I'm more worried about vignetting effects.

[Rainer]

Rubbish ... not more!



These adapters do not allow to control the aperture of the

EF lens that they adapt ... instead, they come with their own

diaphragm ... well ... the bad thing is ... the diaphragm now is no

longer in the position that was originally intended when the lens

was constructed ... rather than that, it now is between the rear

element of the lens and the sensor.



Just my 2cts ... Rainer

[youpii]

[quote name='Lars' timestamp='1291887332' post='4899']

Hello,

there are now Adapters for EF-lenses available with built-in aperture:

http://www.dl-kipon.com/en/articledetail.asp?id=30

http://www.43rumors.com/new-canon-eos-to-micro-four-thirds-adapter-with-built-in-aperture-control/



So, a question for the optics-specialists:

As I assume, the position of the aperture blades in the lens ist important for the IQ.

What do you think?

Is the IQ degraded if you close this aperture within the adapter?



Thanks

Lars

[/quote]



I wonder how long it will take before someone design a chip to translate NEW & M4/3 commands to Canon aperture commands

[wim]

Hi Lars,

[quote name='Lars' timestamp='1291887332' post='4899']

Hello,

there are now Adapters for EF-lenses available with built-in aperture:

[url="http://www.dl-kipon.com/en/articledetail.asp?id=30"]http://www.dl-kipon....etail.asp?id=30[/url]

[url="http://www.43rumors.com/new-canon-eos-to-micro-four-thirds-adapter-with-built-in-aperture-control/"]http://www.43rumors....erture-control/[/url]



So, a question for the optics-specialists:

As I assume, the position of the aperture blades in the lens ist important for the IQ.

What do you think?

Is the IQ degraded if you close this aperture within the adapter?



Thanks

Lars

[/quote]

The position of the diaphragm generally determines the amount of barrel or pincushion distortion one gets. Depending on the lens design you may start seeing this effect. Furthermore, one has to wonder about reflections of this probably quite cheap diaphragm with regard to all kinds of IQ-degrading effects. I obviously have never used any of these, and being able to stop down in some cases is better than not being able to stop down, but in such cases i would rather buy a good old manual everything lens and fit a plain adapter to it. Actually, that is exactly what I do <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />.



Kind regards, Wim

[genotypewriter]

[quote name='Lars' timestamp='1291887332' post='4899']

So, a question for the optics-specialists:

As I assume, the position of the aperture blades in the lens ist important for the IQ.

What do you think?

Is the IQ degraded if you close this aperture within the adapter?

[/quote]

Moving the aperture further to the back of the lens moves the exit pupil closer to the sensor. There are several layers of flat glass on typical digital sensors (for IR-cut, AA-filter, dust removal, etc.) that are thick enough to cause refraction of light (and introduce their own aberrations like CA). So putting the exit pupil further back will make the exiting light rays hit the sensor more angled than they would if the lens was using its own aperture which is further away from the sensor. I'll leave it at that <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='' />



GTW



PS: But didn't anyone notice how nice and round those apertures are? Wish they made apertures like that in modern lenses.