December 18, 2017, 04:02:53 PM

Author Topic: Mirror box bokeh clipping haunts my dreams  (Read 3588 times)

mb66energy

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #15 on: December 02, 2017, 09:25:48 AM »
Could the mirror box be designed to eliminate this phenomenon?  Rounded or tapered

Remove everything which is between the circular opening of the lens and the sensor. Or buy a mirrorless camera - it has not mirrorbox and hopefully nothing which interferes with the lens and the sensor. Would be great to see some images of FF mirrorless cameras with the EF 85 1.2 adapted ...

Definitely a strong drawback for ME because it looks very unnatural.
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Re: Mirror box bokeh clipping haunts my dreams
« Reply #15 on: December 02, 2017, 09:25:48 AM »

IglooEater

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #16 on: December 02, 2017, 09:30:34 AM »
Huh, thank you AH–this is very interesting. I personally don’t have any lenses that could generate that phenomenon, but I enjoy knowing about these things.

hne

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #17 on: December 02, 2017, 09:43:48 AM »
Could the mirror box be designed to eliminate this phenomenon?  Rounded or tapered

They were. Look at pretty much any film EOS camera and you'll see a cut out at the bottom.
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9VIII

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #18 on: December 02, 2017, 11:24:58 AM »
Don’t forget the Canon 85f1.2 has the electronic contacts on the rear element itself.
Bokeh on that lens will look a bit funky no matter what design the body has.

Sharlin

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #19 on: December 02, 2017, 12:11:19 PM »
I actually asked about this on Photo.StackExchange a few years ago, related to the old Sigma 30mm f/1.4 EX DC! Was a bit nonplussed when I saw the clipping for the first time. I'm not sure whether the new Art version exhibits the issue.

hne

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #20 on: December 03, 2017, 07:05:27 AM »
So if you have a large aperture prime, a few questions come to mind:

1) Which Canon lenses demonstrate this phenomenon?  Does the 135L as well?  Does the Sigma Art 85 or 135 do this?  Otus glass, perhaps?

2) How does one get round/soft/large bokeh balls from a large aperture lens?  Just stop it down and forego the size/softness of the large aperture to eliminate the clipping?  (Wouldn't that defeat the point of buying the fast lens?)

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1) As this is strictly geometric, with the same f number always having the same light cone angle from pixel to exit aperture, the placement of rear element makes no difference since it can't be larger than the rectangular hole of the mirror box. The mirror box intersects the light cones for some parts of the image starting at about f/1.8 at the extreme top for the 5DmkIV mirror box. The 5DmkII has a deeper cut out at the bottom but clips slightly more so is probably smaller. Haven't measured.

2) if you want perfectly round bokeh balls, you need to buy slower lenses than f/1.8 (with humongous front elements to avoid cat's eye bokeh), stop down to at least f/2 or use only the centre part of the frame.
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ahsanford

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #21 on: December 03, 2017, 08:33:30 PM »
2) if you want perfectly round bokeh balls, you need to buy slower lenses than f/1.8 (with humongous front elements to avoid cat's eye bokeh), stop down to at least f/2 or use only the centre part of the frame.

I'm not convinced that's true.  Here's an 85mm f/1.4 lens on a FF sensored SLR, in this case a Nikon D810 -- I don't see any clipping.

https://www.youtube.com/watch?v=E4RXQNAeCeo

So either Nikon has a much larger mirror box (for the same size sensor?), or there might be a lens design component to this.

I tried to find some background lighting bokeh balls for other fast 85s (including Dustin Abbott's site) and struck out.  If someone has 3rd party lens 85 1.4 samples on a Canon FF rig, please share.

- A

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #21 on: December 03, 2017, 08:33:30 PM »

jd7

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #22 on: December 04, 2017, 04:14:51 AM »
2) if you want perfectly round bokeh balls, you need to buy slower lenses than f/1.8 (with humongous front elements to avoid cat's eye bokeh), stop down to at least f/2 or use only the centre part of the frame.

I'm not convinced that's true.  Here's an 85mm f/1.4 lens on a FF sensored SLR, in this case a Nikon D810 -- I don't see any clipping.

https://www.youtube.com/watch?v=E4RXQNAeCeo

So either Nikon has a much larger mirror box (for the same size sensor?), or there might be a lens design component to this.

I tried to find some background lighting bokeh balls for other fast 85s (including Dustin Abbott's site) and struck out.  If someone has 3rd party lens 85 1.4 samples on a Canon FF rig, please share.

- A

Any of these any good to you?

https://www.flickr.com/photos/wefwef/5198757019/in/dateposted/
https://www.flickr.com/photos/wefwef/5182085737/in/dateposted/
https://www.flickr.com/photos/wefwef/5150349093/in/dateposted/
https://www.flickr.com/photos/wefwef/5205019328/in/dateposted/
https://www.flickr.com/photos/wefwef/5218131465/in/dateposted/


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arthurbikemad

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #23 on: December 04, 2017, 04:44:49 AM »
Check out the 35/1.4II. Has perfect Bokeh imo.

hne

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #24 on: December 04, 2017, 07:51:51 AM »
2) if you want perfectly round bokeh balls, you need to buy slower lenses than f/1.8 (with humongous front elements to avoid cat's eye bokeh), stop down to at least f/2 or use only the centre part of the frame.

I'm not convinced that's true.  Here's an 85mm f/1.4 lens on a FF sensored SLR, in this case a Nikon D810 -- I don't see any clipping.

https://www.youtube.com/watch?v=E4RXQNAeCeo

So either Nikon has a much larger mirror box (for the same size sensor?), or there might be a lens design component to this.

I tried to find some background lighting bokeh balls for other fast 85s (including Dustin Abbott's site) and struck out.  If someone has 3rd party lens 85 1.4 samples on a Canon FF rig, please share.

- A

Any of these any good to you?

https://www.flickr.com/photos/wefwef/5198757019/in/dateposted/
https://www.flickr.com/photos/wefwef/5182085737/in/dateposted/
https://www.flickr.com/photos/wefwef/5150349093/in/dateposted/
https://www.flickr.com/photos/wefwef/5205019328/in/dateposted/
https://www.flickr.com/photos/wefwef/5218131465/in/dateposted/

They all show clipped OOF balls.
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hne

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #25 on: December 04, 2017, 08:37:43 AM »
2) if you want perfectly round bokeh balls, you need to buy slower lenses than f/1.8 (with humongous front elements to avoid cat's eye bokeh), stop down to at least f/2 or use only the centre part of the frame.

I'm not convinced that's true.  Here's an 85mm f/1.4 lens on a FF sensored SLR, in this case a Nikon D810 -- I don't see any clipping.

https://www.youtube.com/watch?v=E4RXQNAeCeo

So either Nikon has a much larger mirror box (for the same size sensor?), or there might be a lens design component to this.

I tried to find some background lighting bokeh balls for other fast 85s (including Dustin Abbott's site) and struck out.  If someone has 3rd party lens 85 1.4 samples on a Canon FF rig, please share.

- A

hen you record a video in 16:9 aspect ratio, you cut off 5% top and bottom which likely hides rather efficiently also on your Canon DSLR.
The Nikon F mount has a 2.5mm longer flange focal distance and as such ought to be more susceptible to this. It could very well be the case that Nikon is using a wider opening on its mirror boxes than Canon does.

That said, the phenomenon is there on the...
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D750: https://www.flickr.com/photos/stephanrudolph/31296328703/
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D800E: https://www.flickr.com/photos/charliemcmahon/26360753869/
D810: https://www.flickr.com/photos/51290195@N07/15574134554/
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bholliman

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #26 on: December 04, 2017, 08:41:12 AM »
2) if you want perfectly round bokeh balls, you need to buy slower lenses than f/1.8 (with humongous front elements to avoid cat's eye bokeh), stop down to at least f/2 or use only the centre part of the frame.

My understanding is that the Sigma Art 85mm f/1.4 has perfectly round bokeh balls wide open, with no mirror box clipping.  If that is true, is it due to the large front element (86mm)?
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neuroanatomist

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #27 on: December 04, 2017, 09:15:32 AM »
My understanding is that the Sigma Art 85mm f/1.4 has perfectly round bokeh balls wide open, with no mirror box clipping.  If that is true, is it due to the large front element (86mm)?

Your understanding is incorrect.  For example, see the set of Flickr images posted by jd7, which are with the Sigma 85A.  A couple of images from that set are highlighted below.
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Re: Mirror box bokeh clipping haunts my dreams
« Reply #27 on: December 04, 2017, 09:15:32 AM »

hne

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #28 on: December 04, 2017, 09:18:19 AM »
2) if you want perfectly round bokeh balls, you need to buy slower lenses than f/1.8 (with humongous front elements to avoid cat's eye bokeh), stop down to at least f/2 or use only the centre part of the frame.

My understanding is that the Sigma Art 85mm f/1.4 has perfectly round bokeh balls wide open, with no mirror box clipping.  If that is true, is it due to the large front element (86mm)?

Then your understanding is incorrect: https://www.lensrentals.com/blog/wp-content/gallery/nicks-wedding-photography-sigma-85mm-f1-4-examples/Sigma-85mm-Art-Series-Example-Photo-3.jpg
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stevelee

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #29 on: December 04, 2017, 02:20:15 PM »
In the examples, I would find the out of focus balls distracting even if they were all perfectly round.

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Re: Mirror box bokeh clipping haunts my dreams
« Reply #29 on: December 04, 2017, 02:20:15 PM »