A1 aperture sweetspot? at DVinfo.net

Toenis Liivamaegi · January 8th, 2007, 10:49 AM

What would be the A1 aperture sweetspot?
Should f3.4 be fine? I`m thinking about using M2 DOF adapter or similar and as far as I know there are drastic improvements in sharpness when iris is colsed down a bit. Sorry, I just haven`t got the time to experiment right now.

Thanks in advance,
T

Michael Mann · January 8th, 2007, 12:46 PM

Toenis, just from accurately watching my own wide angle footage so far I'd say that closing the open aperture at least by one stop improves the sharpness. I wouldn't call it a drastic improvement, but I find it visible (even downsized, on a 1280 x 1024 display).

Tom Roper · January 8th, 2007, 07:42 PM

The results from using the Imatest MTF50/MTF50P spatial frequency reference testing shows the greatest resolution and contrast is at F3.7.

Anything in the range of F3.1 to F4.4 is nearly perfect, if you shoot at F9.5 the image loses sharpness and contrast significantly. Use the ND filters to avoid the small iris openings in bright light.

This is a case not unlike other Canon "L" series lenses. The best performance comes at surprisingly large aperture openings. This lens is even sharp wide open F1.6.

Try it at F3.7. The image will really "pop."

But drastic improvements in sharpness when the iris is closed down? Not with this lens!

Noel Evans · January 9th, 2007, 01:46 AM

Just stated on another thread, I am using -3 sharpness generally, but with the m2 im upping that to 0. The A1 is pretty tack sharp from wide open and well up the range, so there shouldnt be any issue there, considering, with the light loss caused by the 35mm adapters you're pretty much always on the open end of the scale.

Toenis Liivamaegi · January 9th, 2007, 02:08 AM

Thanks Tom.

What I meant with drastic resolution improvement is when camcorder is used with a DOF adaptor as images from those tend to really pop when camcorder`s aperture is set at sweetspot.

Cheers,
T

Chris Zinner · January 9th, 2007, 09:16 PM

hi there!

this thread sounds really interesting as we have purchased about the same setup some days ago. we got the g1 and it works really nice. got some problems with the M2 though as it is slightly tilted which seems to be a production fault. we are sure that we can fix this so be it. other than that it seems that the M2 is positioned about 1/2mm too low for the camera's acromat to be perfectly vertically aligned. our M2 needs to be shimmed.
i got some questions about your setup.
did you had to correct the M2's position or did your's just fit?
another question would be if you had any problems getting focus onto the groundglass? i heard something about that in another forum i think. could you give me some tips about that?

thx for the information on the sweetspot thing guys. we'll surely check that out when everything is put together. if this is too much off topic with all the questions please pm me.

thx,
cya

January 8th, 2007, 10:49 AM	#1
Toenis Liivamaegi Major Player Join Date: Nov 2005 Location: Tartu, Estonia Posts: 579	A1 aperture sweetspot? What would be the A1 aperture sweetspot? Should f3.4 be fine? I`m thinking about using M2 DOF adapter or similar and as far as I know there are drastic improvements in sharpness when iris is colsed down a bit. Sorry, I just haven`t got the time to experiment right now. Thanks in advance, T

January 8th, 2007, 12:46 PM	#2
Michael Mann Major Player Join Date: Dec 2005 Location: Kelkheim, Germany Posts: 375	Toenis, just from accurately watching my own wide angle footage so far I'd say that closing the open aperture at least by one stop improves the sharpness. I wouldn't call it a drastic improvement, but I find it visible (even downsized, on a 1280 x 1024 display). __________________ Michael

January 8th, 2007, 07:42 PM	#3
Tom Roper Trustee Join Date: Jun 2004 Location: Denver, Colorado Posts: 1,891	The results from using the Imatest MTF50/MTF50P spatial frequency reference testing shows the greatest resolution and contrast is at F3.7. Anything in the range of F3.1 to F4.4 is nearly perfect, if you shoot at F9.5 the image loses sharpness and contrast significantly. Use the ND filters to avoid the small iris openings in bright light. This is a case not unlike other Canon "L" series lenses. The best performance comes at surprisingly large aperture openings. This lens is even sharp wide open F1.6. Try it at F3.7. The image will really "pop." But drastic improvements in sharpness when the iris is closed down? Not with this lens!

January 9th, 2007, 01:46 AM	#4
Noel Evans Regular Crew Join Date: Feb 2006 Location: Tokyo, Japan Posts: 157	Just stated on another thread, I am using -3 sharpness generally, but with the m2 im upping that to 0. The A1 is pretty tack sharp from wide open and well up the range, so there shouldnt be any issue there, considering, with the light loss caused by the 35mm adapters you're pretty much always on the open end of the scale.

January 9th, 2007, 02:08 AM	#5
Toenis Liivamaegi Major Player Join Date: Nov 2005 Location: Tartu, Estonia Posts: 579	Thanks Tom. What I meant with drastic resolution improvement is when camcorder is used with a DOF adaptor as images from those tend to really pop when camcorder`s aperture is set at sweetspot. Cheers, T

January 9th, 2007, 09:16 PM	#6
Chris Zinner New Boot Join Date: Apr 2006 Location: vienna austria Posts: 13	hi there! this thread sounds really interesting as we have purchased about the same setup some days ago. we got the g1 and it works really nice. got some problems with the M2 though as it is slightly tilted which seems to be a production fault. we are sure that we can fix this so be it. other than that it seems that the M2 is positioned about 1/2mm too low for the camera's acromat to be perfectly vertically aligned. our M2 needs to be shimmed. i got some questions about your setup. did you had to correct the M2's position or did your's just fit? another question would be if you had any problems getting focus onto the groundglass? i heard something about that in another forum i think. could you give me some tips about that? thx for the information on the sweetspot thing guys. we'll surely check that out when everything is put together. if this is too much off topic with all the questions please pm me. thx, cya