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Aperture Control Adapter Question
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PostPosted: Tue Feb 11, 2020 8:07 am    Post subject: Aperture Control Adapter Question Reply with quote

Hi Everyone:

I just purchased a Rodenstock Heligon 95mm f0.95 projector lens for a Sony mount, to be used on my Sony A7ii. The lens however is a little soft wide open, so I thought to get an aperture control adapter. I am hoping to increase sharpness and eliminate a little vignetting on my full frame camera. The aperture control adapters I have seen all seem to work from a different mount (such as Canon) to the Sony mount. So I am not sure how this can work. Is there such an aperture control adapter from an e mount to an e mount? If not, is there anything else I can do?

Thanks,

Charles


PostPosted: Tue Feb 11, 2020 9:02 am    Post subject: Re: Aperture Control Adapter Question Reply with quote

charley5 wrote:
Hi Everyone:

I just purchased a Rodenstock Heligon 95mm f0.95 projector lens for a Sony mount, to be used on my Sony A7ii. The lens however is a little soft wide open, so I thought to get an aperture control adapter. I am hoping to increase sharpness and eliminate a little vignetting on my full frame camera. The aperture control adapters I have seen all seem to work from a different mount (such as Canon) to the Sony mount. So I am not sure how this can work. Is there such an aperture control adapter from an e mount to an e mount? If not, is there anything else I can do?

Thanks,

Charles


Welcome Here Charles!

I have done similar, but be advised that rear mounted apertures often lead to (severe) vignetting, so the better solution would be a front aperture, even a simple cardboard one would do...


PostPosted: Tue Feb 11, 2020 11:53 pm    Post subject: aperture control mechanism... a no go! Reply with quote

This article basically smashes my idea about installing an aperture control mechanism either in front of or behind the lens. Either way the resulting vignetting is unacceptable.

https://www.davidkennardphotography.com/blog/1076-adding-an-aperture-to-an-irisless-lens.xhtml


PostPosted: Wed Feb 12, 2020 12:20 am    Post subject: Re: aperture control mechanism... a no go! Reply with quote

charley5 wrote:
This article basically smashes my idea about installing an aperture control mechanism either in front of or behind the lens. Either way the resulting vignetting is unacceptable.

https://www.davidkennardphotography.com/blog/1076-adding-an-aperture-to-an-irisless-lens.xhtml


Well, it massively depends on the focal length and speed of th elens used; loger focal lengths tenfs to much less vignetting.
I woudl try a front cardboard "iris" an see what it does...not much effort.


PostPosted: Wed Feb 12, 2020 1:23 am    Post subject: Front-end aperture control. Reply with quote

I see. Thanks Klaus. I shall give it a try then. Stopping down at either end didn't seem to affect sharpness. But I have nothing to lose.


PostPosted: Wed Feb 12, 2020 2:57 am    Post subject: Re: aperture control mechanism... a no go! Reply with quote

charley5 wrote:
This article basically smashes my idea about installing an aperture control mechanism either in front of or behind the lens. Either way the resulting vignetting is unacceptable.

https://www.davidkennardphotography.com/blog/1076-adding-an-aperture-to-an-irisless-lens.xhtml


Garbage in garbage out. Front of lens aperture extends too far in front of lens' front element acts more like too long hood when closed down thus vignette, however increase in dof is apparent, i.e. front aperture works, rear no. Aperture closer to front element less vignette.


PostPosted: Wed Feb 12, 2020 9:58 am    Post subject: Re: Aperture Control Adapter Question Reply with quote

kds315* wrote:


I have done similar, but be advised that rear mounted apertures often lead to (severe) vignetting, so the better solution would be a front aperture, even a simple cardboard one would do...


I've used black paper ones on my 50/1.2 projector & tested them on a couple of others. Made so they fit tight up against the front element, plain circular cut outs work in a similar way to an Iris at least if you get the hole sizes right. Using different shaped cut outs allows you to shape the bokeh too!
Like this: https://flic.kr/p/27KRhGp

On another occasion I tried a large iris held as close as possible to the lens. It worked for some of my projector lenses but others had front elements that where recessed to far giving rise to vignetting. I've not tried the iris since.


PostPosted: Fri Feb 14, 2020 3:20 am    Post subject: Re: aperture control mechanism... a no go! Reply with quote

visualopsins wrote:
charley5 wrote:
This article basically smashes my idea about installing an aperture control mechanism either in front of or behind the lens. Either way the resulting vignetting is unacceptable.

https://www.davidkennardphotography.com/blog/1076-adding-an-aperture-to-an-irisless-lens.xhtml


Garbage in garbage out. Front of lens aperture extends too far in front of lens' front element acts more like too long hood when closed down thus vignette, however increase in dof is apparent, i.e. front aperture works, rear no. Aperture closer to front element less vignette.


Thanks. That's helpful!


PostPosted: Fri Feb 14, 2020 3:26 am    Post subject: Re: Aperture Control Adapter Question Reply with quote

DConvert wrote:
kds315* wrote:


I have done similar, but be advised that rear mounted apertures often lead to (severe) vignetting, so the better solution would be a front aperture, even a simple cardboard one would do...


I've used black paper ones on my 50/1.2 projector & tested them on a couple of others. Made so they fit tight up against the front element, plain circular cut outs work in a similar way to an Iris at least if you get the hole sizes right. Using different shaped cut outs allows you to shape the bokeh too!
Like this: https://flic.kr/p/27KRhGp

On another occasion I tried a large iris held as close as possible to the lens. It worked for some of my projector lenses but others had front elements that where recessed to far giving rise to vignetting. I've not tried the iris since.


Does it help shape highlights in the background, as you imply on your page? Did you find it sharpened the image a bit as well, given that the aperture was wide open?

Thanks.


PostPosted: Fri Feb 14, 2020 8:22 am    Post subject: Re: Aperture Control Adapter Question Reply with quote

charley5 wrote:
DConvert wrote:
kds315* wrote:


I have done similar, but be advised that rear mounted apertures often lead to (severe) vignetting, so the better solution would be a front aperture, even a simple cardboard one would do...


I've used black paper ones on my 50/1.2 projector & tested them on a couple of others. Made so they fit tight up against the front element, plain circular cut outs work in a similar way to an Iris at least if you get the hole sizes right. Using different shaped cut outs allows you to shape the bokeh too!
Like this: https://flic.kr/p/27KRhGp

On another occasion I tried a large iris held as close as possible to the lens. It worked for some of my projector lenses but others had front elements that where recessed to far giving rise to vignetting. I've not tried the iris since.


Does it help shape highlights in the background, as you imply on your page? Did you find it sharpened the image a bit as well, given that the aperture was wide open?

Thanks.


Yes the OOF highlights take on the shape of the cutout (as shown by the flowers in the linked picture). I couldn't manage shot without the bokeh masks as it was too bright for f/1.2 even at my lowest ISO and I didn't have an ND filter with me, but from the rules of Physics yes it will sharpen up the image/increase DOF. It is possible to make masks that allow light from the outer edges of the lens while blocking the centre portion - those will give a soft focus effect - though I've not done one personally.


PostPosted: Sat Feb 15, 2020 11:17 am    Post subject: Re: Aperture Control Adapter Question Reply with quote

charley5 wrote:
Hi Everyone:

I just purchased a Rodenstock Heligon 95mm f0.95 projector lens for a Sony mount, to be used on my Sony A7ii. The lens however is a little soft wide open, so I thought to get an aperture control adapter. I am hoping to increase sharpness and eliminate a little vignetting on my full frame camera. The aperture control adapters I have seen all seem to work from a different mount (such as Canon) to the Sony mount. So I am not sure how this can work. Is there such an aperture control adapter from an e mount to an e mount? If not, is there anything else I can do?

Thanks,

Charles



Would a focal reducer decrease the risk of vignetting?


PostPosted: Sat Feb 15, 2020 1:00 pm    Post subject: Re: Aperture Control Adapter Question Reply with quote

charley5 wrote:
charley5 wrote:
Hi Everyone:

I just purchased a Rodenstock Heligon 95mm f0.95 projector lens for a Sony mount, to be used on my Sony A7ii. The lens however is a little soft wide open, so I thought to get an aperture control adapter. I am hoping to increase sharpness and eliminate a little vignetting on my full frame camera. The aperture control adapters I have seen all seem to work from a different mount (such as Canon) to the Sony mount. So I am not sure how this can work. Is there such an aperture control adapter from an e mount to an e mount? If not, is there anything else I can do?

Thanks,

Charles



Would a focal reducer decrease the risk of vignetting?


No it will definitely make it MUCH worse. A smaller aperture as Charles was suggesting can improve a lenses coverage and will certainly help with vignetting if it's in the right place. In the wrong place an added aperture can make vignetting worse.


PostPosted: Sun Mar 15, 2020 1:52 pm    Post subject: Reply with quote

Most projector lenses have the rear element way up the barrel. Perhaps a cut aperture pushed up against the rear lens will work