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Archive 2013 · Sensor filter removal/replacement thread

  
 
sebboh
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p.3 #1 · p.3 #1 · Sensor filter removal/replacement thread


dnhkng wrote:
I wonder if taking a picture of a fine-weave fabric would find it quickly. I would expect moiré pattern along the line of focus, disappearing at some point away from the line with a distance proportional to the amount tilt.


couldn't hurt to try it. getting perfect alignment of camera to fabric will be just as hard as getting perfect alignment of camera to test chart.






Dec 23, 2013 at 04:07 PM
RCicala
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p.3 #2 · p.3 #2 · Sensor filter removal/replacement thread


sebboh wrote:
i just read Roger's article and i have to say i don't follow the logic of his conclusions in a number of cases. perhaps he can chime in to tell me what i'm missing.

he says: "So why would the Zeiss 35mm f/2 fare worse on the camera, while it is probably the best lens of the three tested on the optical bench?"

but the results he shows from the optical bench indicate that the ZE 35/2 is the worst lens on the optical bench in the center and is noticeably worse (particularly at high frequency where it matters for the comparison)
...Show more


I can't answer everything (because I don't know), but I do want to clarify I misstated the lens order in the article. In my first draft I compared just the Zeiss and Sony (the Zeiss is better off camera). Then I went back and added the Canon lens but didn't make the proper correction in the test. The Canon does outresolve both the Sony and the Zeiss off camera.
So off camera, the results were Canon > Zeiss > Sony. On camera it was Sony barely> Canon >> Zeiss

As to adapters - I'm looking at a 36 point horizontal and vertical resolution set, which I don't reproduce in the article. It's extremely sensitive to tilt - and Imatest measures tilt in addition. I ran multiple lenses on multiple adapters and took the results from the one with the least tilt. Given % change in resolution and astigmatism, the amount of tilt here is no more than the variation I'd see in multiple copies of a lens on one camera - around 0.04 of a degree.

Don't get me wrong - I don't advocate testing on adapters for just this reason. But in this case there's not much option I can think of.



Dec 23, 2013 at 04:15 PM
sebboh
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p.3 #3 · p.3 #3 · Sensor filter removal/replacement thread



RCicala wrote:
I can't answer everything (because I don't know), but I do want to clarify I misstated the lens order in the article. In my first draft I compared just the Zeiss and Sony (the Zeiss is better off camera). Then I went back and added the Canon lens but didn't make the proper correction in the test. The Canon does outresolve both the Sony and the Zeiss off camera.
So off camera, the results were Canon > Zeiss > Sony. On camera it was Sony barely> Canon >> Zeiss

As to adapters - I'm looking at a 36 point horizontal and
...Show more

just to be clear here: you're saying that the tilt value, as measured by imatest, gave comparable average values for the a7r + ZA 35/2.8 as it did for a7r + adapter + canon mount lens?




Dec 23, 2013 at 05:03 PM
RCicala
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p.3 #4 · p.3 #4 · Sensor filter removal/replacement thread


sebboh wrote:
just to be clear here: you're saying that the tilt value, as measured by imatest, gave comparable average values for the a7r + ZA 35/2.8 it did for a7r + adapter + canon mount lens?



No, not average. I'm saying with a bit of selection I was able to get adapters that were pretty close. That still left one corner a bit soft on Imatest and created a bit of astigmatism, but just a little - worst corner around 80% MTF values of best corner, which isn't unusual in lenses mounted directly to the camera.

I don't think I could shim any closer than that.



Dec 23, 2013 at 05:09 PM
sebboh
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p.3 #5 · p.3 #5 · Sensor filter removal/replacement thread




RCicala wrote:
No, not average. I'm saying with a bit of selection I was able to get adapters that were pretty close. That still left one corner a bit soft on Imatest and created a bit of astigmatism, but just a little - worst corner around 80% MTF values of best corner, which isn't unusual in lenses mounted directly to the camera.

I don't think I could shim any closer than that.


I mean for the lenses and adapters used in this test. I'm asking because it seems adapters could easily be the source of your optical bench/imatest discrepancy.




Dec 23, 2013 at 05:15 PM
RCicala
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p.3 #6 · p.3 #6 · Sensor filter removal/replacement thread


The ones used in the test were very close to square, with less than a fraction of a degree of tilt.

That being said, having tested many dozen lenses on adapter, I've never, ever seen one that was perfect. Since we know the camera's mount can't be made perfectly square to the sensor without variation, nor can the mount on the lens, there's certainly no way two more mount interfaces on an adapter can be perfect. Close is the best I hoped for, and close is what we got.




Dec 23, 2013 at 06:12 PM
dasrocket
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p.3 #7 · p.3 #7 · Sensor filter removal/replacement thread


I think we will start seeing such sensor mods as folks get closer to the end of the Sony warranty.

If the glass removal really does make a big difference these bodies may enjoy a renewed interest..



Dec 23, 2013 at 06:27 PM
Tmuussoni
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p.3 #8 · p.3 #8 · Sensor filter removal/replacement thread


I'm shamelessly bumbing this thread. Still nobody has tried this?

I would be really curious to see about the results.. too bad



Apr 17, 2014 at 09:07 AM
FlyPenFly
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p.3 #9 · p.3 #9 · Sensor filter removal/replacement thread


With something like 5 axis sensor shifting, one would think that one day someone could make a camera auto calibrate a lens by serial number to shift the sensor to be perfectly square with the lens.


Apr 17, 2014 at 09:56 AM
Beni
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p.3 #10 · p.3 #10 · Sensor filter removal/replacement thread


I'd love to know if the adaptor with glass is ever going to happen. Rather dispairing of finding a small 24mm with good corners. You either get the Zeiss 25mm which is far from small on the A7r or the Sony Zeiss which is similarly large. Other than that, tough luck.


Apr 17, 2014 at 11:50 AM
sebboh
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p.3 #11 · p.3 #11 · Sensor filter removal/replacement thread


Beni wrote:
I'd love to know if the adaptor with glass is ever going to happen. Rather dispairing of finding a small 24mm with good corners. You either get the Zeiss 25mm which is far from small on the A7r or the Sony Zeiss which is similarly large. Other than that, tough luck.


i'm betting it won't.

shortening the sensor stack after market seems like a better bet to me.




Apr 17, 2014 at 11:59 AM
FlyPenFly
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p.3 #12 · p.3 #12 · Sensor filter removal/replacement thread


I think people have had luck with the Olympus 24mm F2.

I myself have been pondering the Rokinon 24mm F1.4. I'm just not sure about the size.



Apr 17, 2014 at 02:19 PM
_julian_
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p.3 #13 · p.3 #13 · Sensor filter removal/replacement thread


The usual construction has the first birefringent layer of the filter stack epoxied to the ceramic carrier. Most folks doing filter mods use a heat-gun to pop it off.

http://youtu.be/Wh12RY2mu_A?t=3m

I've tested this with a NEX 5n sensor, but not a fullframe sensor.




Apr 17, 2014 at 05:21 PM
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