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Archive 2009Cut Bokeh Circles
p.1 #1Cut Bokeh Circles
I didn't know which part of the forum this belongs to, but since it's gear specific, I decided to put it here.
I noticed that my Minolta 58 1.2 cuts bokeh circles at the bottom of the frame. It only happens wide open at the bottom of the frame. It goes away around f1.4-f2
http://farm3.static.flickr.com/2639/4227630772_95d90b9f5f.jpg
This is in portrait position, and the physical bottom of the frame is on the left side. I googled around and found only one post on flickr about this. The poster stated that the only wide aperture lenses (s)he knew not to suffer from this are Leica (on Leica bodies). This was taken with Canon 7D.
Is this expected? My 50 1.8 doesn't do that, but neither does the Minolta at 1.8.
Thanks.
I noticed that my Minolta 58 1.2 cuts bokeh circles at the bottom of the frame. It only happens wide open at the bottom of the frame. It goes away around f1.4-f2
http://farm3.static.flickr.com/2639/4227630772_95d90b9f5f.jpg
This is in portrait position, and the physical bottom of the frame is on the left side. I googled around and found only one post on flickr about this. The poster stated that the only wide aperture lenses (s)he knew not to suffer from this are Leica (on Leica bodies). This was taken with Canon 7D.
Is this expected? My 50 1.8 doesn't do that, but neither does the Minolta at 1.8.
Thanks.
Dec 31, 2009 at 02:07 PM
p.1 #2Cut Bokeh Circles
This happens when mirror box interferes with optical path. Happens more with cropped cameras with smaller mirror boxes.
Dec 31, 2009 at 02:57 PM
p.1 #3Cut Bokeh Circles
I have no idea.
Stop down to f/22 or something like that. Press the DOF preview button. The shape the blades make (point the lens at yourself while the DOF preview is on) is going to be the same shape as OOF highlights. Maybe one of the blades is caught, so it isn't closing to complete the circle. Just a guess.
Stop down to f/22 or something like that. Press the DOF preview button. The shape the blades make (point the lens at yourself while the DOF preview is on) is going to be the same shape as OOF highlights. Maybe one of the blades is caught, so it isn't closing to complete the circle. Just a guess.
Dec 31, 2009 at 03:35 PM
p.1 #4Cut Bokeh Circles
ptys,
Put this over on the Alt Gear Forum - a.k.a. - the Rokkor Channel. You'll get a lot of responses - they're busy with Zeiss right now and could use a good new Rokkor thread.
I know this has been discussed before - you could try a search.
mt-m - you may be correct, however, I get the truncated cat's eye on a full frame.
Put this over on the Alt Gear Forum - a.k.a. - the Rokkor Channel. You'll get a lot of responses - they're busy with Zeiss right now and could use a good new Rokkor thread.
I know this has been discussed before - you could try a search.
mt-m - you may be correct, however, I get the truncated cat's eye on a full frame.
Dec 31, 2009 at 04:21 PM
p.1 #5Cut Bokeh Circles
mt-m wrote:
This happens when mirror box interferes with optical path. Happens more with cropped cameras with smaller mirror boxes.
+1 on the mirror box.
EBH
This happens when mirror box interferes with optical path. Happens more with cropped cameras with smaller mirror boxes.
+1 on the mirror box.
EBH
Dec 31, 2009 at 06:46 PM
p.1 #6Cut Bokeh Circles
mMontag wrote:
mt-m - you may be correct, however, I get the truncated cat's eye on a full frame.
"cat's eye" effect is internal vignetting of the lens elements. Vertical or horizontal cutoff is definitely the result of the mirror box. It happens on full-frame cameras too.
mt-m - you may be correct, however, I get the truncated cat's eye on a full frame.
"cat's eye" effect is internal vignetting of the lens elements. Vertical or horizontal cutoff is definitely the result of the mirror box. It happens on full-frame cameras too.
Dec 31, 2009 at 07:54 PM
p.1 #7Cut Bokeh Circles
Me, too. This is with my EF50/1.4 on my 10D:
http://deanwcains.smugmug.com/photos/118082495_ctkHR-L.jpg
http://deanwcains.smugmug.com/photos/118082495_ctkHR-L.jpg
Dec 31, 2009 at 08:32 PM
p.1 #8Cut Bokeh Circles
dcains wrote:
Me, too. This is with my EF50/1.4 on my 10D:
http://deanwcains.smugmug.com/photos/118082495_ctkHR-L.jpg
I'm thinking now that it has nothing to do with the aperture blades, otherwise all of the bokeh would be identical.
Me, too. This is with my EF50/1.4 on my 10D:
http://deanwcains.smugmug.com/photos/118082495_ctkHR-L.jpg
I'm thinking now that it has nothing to do with the aperture blades, otherwise all of the bokeh would be identical.
Dec 31, 2009 at 08:41 PM
p.1 #9Cut Bokeh Circles
Here, you can start to see the result of the aperture blades. Same setup, but this shot is at f/2.8 versus f/1.4:
http://deanwcains.smugmug.com/photos/118082852_p8Dig-L.jpg
Looks like it must be the close proximity of the flipped-up mirror to the top of the sensor (the image is flipped, in-camera) that's the culprit. There's much more clearance near the bottom edge of the sensor because of the well the AF sensor assembly sits in.
http://deanwcains.smugmug.com/photos/118082852_p8Dig-L.jpg
Looks like it must be the close proximity of the flipped-up mirror to the top of the sensor (the image is flipped, in-camera) that's the culprit. There's much more clearance near the bottom edge of the sensor because of the well the AF sensor assembly sits in.
Dec 31, 2009 at 08:47 PM
p.1 #10Cut Bokeh Circles
Dpic_arctic wrote:
I have no idea.
Stop down to f/22 or something like that. Press the DOF preview button. The shape the blades make (point the lens at yourself while the DOF preview is on) is going to be the same shape as OOF highlights. Maybe one of the blades is caught, so it isn't closing to complete the circle. Just a guess.
How could this be? as it would show in all the circles and the OP states it only happens wide open not stopped down even a stop
I have no idea.
Stop down to f/22 or something like that. Press the DOF preview button. The shape the blades make (point the lens at yourself while the DOF preview is on) is going to be the same shape as OOF highlights. Maybe one of the blades is caught, so it isn't closing to complete the circle. Just a guess.
How could this be? as it would show in all the circles and the OP states it only happens wide open not stopped down even a stop
Jan 01, 2010 at 04:45 AM
p.1 #11Cut Bokeh Circles
Dpic_arctic wrote:
I have no idea.
Stop down to f/22 or something like that. Press the DOF preview button. The shape the blades make (point the lens at yourself while the DOF preview is on) is going to be the same shape as OOF highlights. Maybe one of the blades is caught, so it isn't closing to complete the circle. Just a guess.
Ian.Dobinson wrote:
How could this be? as it would show in all the circles and the OP states it only happens wide open not stopped down even a stop
Yes, I changed my mind about that, as I noted in a couple posts up.
I have no idea.
Stop down to f/22 or something like that. Press the DOF preview button. The shape the blades make (point the lens at yourself while the DOF preview is on) is going to be the same shape as OOF highlights. Maybe one of the blades is caught, so it isn't closing to complete the circle. Just a guess.
Ian.Dobinson wrote:
How could this be? as it would show in all the circles and the OP states it only happens wide open not stopped down even a stop
Yes, I changed my mind about that, as I noted in a couple posts up.
Jan 02, 2010 at 04:04 PM