OLPF-mod/fish-net/back-filter for Moire?

DrBlaz said:
very interesting.

May be this is a dumb idea, but what would happen cutting a soften filter and putting it in the back of the lens?
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I don't know the details but optical low pass filters work very differently than soften filters. They also block IR via a special coating.
 
Let's say that we/I get this whole OLPF swap done and it works. Who here has a proper resolution chart or zone chart to get a measureable value?
 
Barry does, and I bet he'd get one, and want to test it. Barry?

IR coating would be a must, and it wouldn't make the OLPF any bigger. Also, filtering one way and not the other seems like a horrible mod to do, even if something like 70% of the issue was handled. The main thing is that you are getting a $700 to $2,500 body and destroying it's main feature, stills, and you have to pay for that. I know it would still be worth it, but it would hurt to do something as complicated as this and not get it practically perfect. I BET you would be able to sell 100, the thing is getting the shop doing the transplant involved and committed, giving them the exclusive. Also a few forum posts, here, 5D, and DV, and presto... just make sure to test it properly with someone like Barry FIRST, then post the results... people would go bananas and all it would take is three identical well written, sample packed posts.

Sounds simple, but it would be a lot of work... that would pay off if the results where perfect.
 
sorry I mean a soften filter or caprock or any available.


I found this web,

http://www.optics-online.com/lpf.asp

in the pdf it says:

"When installing the OLPF into the digital imaging system it must be placed between
the lens and the sensor. The performance is dictated by the layer thickness and any
optical coatings on the external surfaces. The exact location along this z-axis does
not affect the performance of the filter significantly."

so the filter could be in the back of the lens, but should the 7d built in filter be removed?
 
That is what I first envisioned. A small filter somehow held in front of the rear element of the lens and flush enough not to bug the mirror. Perhaps different ones for different lenses, matched for that lens, or for that focal length (whatever makes a particular strength work better with each particular lens).

The built-in OLPF would not need to be removed. It would only cut off detail beyond 18MP, and it's IR filtering would still do it's job.
 
I think charts are great if used in the right context. They will never represent absolute image quality because we've all seen really great and really nasty images from HDSLRs but they are great in measuring a delta in image quality.
 
Barry, if I send a T2i modded with the D30 OLPF your way, would you be willing to shoot some tests with it against the 7D and whatever else you can think of?
 
Depending on schedule, certainly. March/April/May are shaping up to be much busier this year, but -- yeah, I'd be glad to put it through the barrage of tests and see how it shapes up!
 
Ahh, so this is what you were talking about Barry :) I did not see this thread.

My initial fear is that what is going to happen is that false detail being removed is going to make softer images and people aren't going to be as happy with the results of the 7D then.

I wish that the sensor had the ability to run in a cropped mode. Meaning, it just used the 1080p pixels from the center of the sensor. Sure, it changes the lens to sensor ratio but for very deep shots, it would probably be a LOT better.

I cannot wait to see some tests on this!
 
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Well, that's kind of what the t2i is supposed to be able to do. But keep in mind you'd have to be very, very far away and use a really, really wide lens to get a decent wide-angle shot out of it. I think I calculated that the t2i's crop mode would deliver about the same FOV as a 1/2" video camera, and even with a Peleng 8mm lens on there, it's still not gonna be a wide-angle shot.
 
Yeah, that is why I marked the Scarlet Cinema off my list, my Canon lens aren't going to do much on the 2/3 and I'd rather not buy a whole bunch of lens that I really don't want.

Hmmm, on the website specs it only lists 640x480 in cropped mode:

http://www.usa.canon.com/consumer/c...TechSpecsTabAct&fcategoryid=139&modelid=19943

From a video standpoint, what is different between the t2i and the 7D? I guess the interesting part will be to see how the sensor handles low light in comparison to the 7D since they appear to be different sensors (max pixels are different) although they have the same pixel density and usable size.

So the APS-C sensor is 22.3 x 14.9 mm with a max usable range of 5,184 x 3,456. I figured for 1920x1080 crop I get 8.259mm x 4.656mm. How do you compare 2:3 to 4:3 in terms of comparing sizes?

I see that a 1/2" sensor is generally 6.4mm x 4.8mm, do you compare the height? Because the width of the image is going to be at least 30% wider from those numbers.

However, that said, compared to the APS-C sensor, point taken. Unless you want some super zoom :) My widest lens is a 10mm Sigma.

(The 2/3" width is about the same as the width of the cropped APS-C. I wonder how wide that is going to look with the 8mm fixed lens on the Scarlet).
 
grimepoch said:
From a video standpoint, what is different between the t2i and the 7D?
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We don't know yet. Probably not much. We know it's a "newly designed sensor", but other than that, I'm waiting for someone to do a comprehensive side-by-side so we know what the differences are.

So the APS-C sensor is 22.3 x 14.9 mm with a max usable range of 5,184 x 3,456. I figured for 1920x1080 crop I get 8.259mm x 4.656mm. How do you compare 2:3 to 4:3 in terms of comparing sizes?
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The 3:2 sensor uses full width and cropped height for 16:9, it uses full height and cropped width for 4:3.

A 16:9 2/3" chip is 9.6mm x 5.4mm. 1/2" is somewhere around 7.4mm x 4.2mm.

I see that a 1/2" sensor is generally 6.4mm x 4.8mm, do you compare the height?
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That's for a 4:3 chip. The 16:9 version would be around 7.4 x 4.2

(The 2/3" width is about the same as the width of the cropped APS-C. I wonder how wide that is going to look with the 8mm fixed lens on the Scarlet).
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8mm isn't very wide on 2/3". It's okay, but it's not what people would consider "wide". 4.5mm is wide. Many 2/3" lenses have a "standard" wide setting of 7.6mm or so. In terms of 35mm still photography, 8mm on 2/3" is about equivalent to a 32mm lens on a still camera.
 
The thing is that if you shoot a cropped sensor to avoid moire, you also lost the S35 sensor qualities, so why not use a proper prosumer video camera at that point?
 
USLatin said:
The thing is that if you shoot a cropped sensor to avoid moire, you also lost the S35 sensor qualities, so why not use a proper prosumer video camera at that point?
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1080p cropped on 18MP S35/APS-C is:

(1920/5184) * 22.3mm = 8.26mm wide which is a hair smaller than 2/3". Not great but thats like having a moire and aliasing free 2/3" interchangeable lens (albeit goofy mount for 2/3") camera for $800. Or better yet, a full HD 4x crop mode for super tele.

Are you getting a T2i USLatin? Are you in Studio City, CA? I need to sort some stuff out with the day job but I'm a go to get the D30 OLPF swap done to a T2i as soon as I can source one and I'd like to pit it against whatever you've got.
 
USLatin said:
The thing is that if you shoot a cropped sensor to avoid moire, you also lost the S35 sensor qualities, so why not use a proper prosumer video camera at that point?
Click to expand...

I was thinking in terms of just having a solution for one camera for really deep focus shots, and I agree when you finally sort through all these things it starts to make you wonder what good is coming out of the idea.

My go to lens is 30mm on my 7D. While I do have a 10mm, I don't use it very often and mostly it gets used for music videos. This is important for me because it seems the 8mm on the Fixed Scarlet as Barry pointed out with work around a 32mm. I can live with that :)

But back to the OLPF mod, we'll just have to wait and see the results. One of the comments I can already see coming with the sharpness loss is why use the 7D then (or t2i), but I am thinking it is still going to perform well in low light (which I use the 7D a lot).
 
shaocaholica said:
(1920/5184) * 22.3mm = 8.26mm wide which is a hair smaller than 2/3".
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Well, it's actually a lot smaller than 2/3". 2/3" = 9.6 x 5.4, which is 51.84 square mm. Your proposed 8.26 x 4.64 yields about 38.33 square mm. 51.84 is a little bit more than 33% bigger than 38.33.

So the difference is pretty substantial, but still in the ballpark. That 8.26 is closer in size to a half-inch sensor than a 2/3" sensor. Even so, I think the idea of a fully-reliable 1/2" alias-free and moire-free 1080p camera would certainly appeal to a lot of folks, at $799! And if it was switchable, so it could see the full sensor for shallow DOF, and the 1/2" (should we call it 5/8"?) mode for flawless footage... that would be pretty compelling.
 
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