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Old February 17th, 2006, 07:06 AM   #76
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In case I wasnt totally clear about the IR filter thing, John, this is the deal. I recieved my M73 with no IR filter at all, so it took (for the most part) monochromatic, soft images. Monochromatic because the sensor is so sensitive to IR that all color pixels are saturated with IR and the actual red/green/blue light readings became so washed out and equalized that everything was one color (which would whitebalance to nearly black and white). The images were soft because from what i understand most lenses are not designed to focus light outside of the visible spectrum into the same plane as RGB. Kind of like bad lenses have chromatic abberation that often results in blue color fringing, in IR imaging, many lenses have white IR fringing that diffuses the image a lot.

Anyway, sumix sent me a filter the screws into the c-mount behind the lens that was branded fillfactory, and it didnt seem to fully remove IR light since there was still limited color information and some image softness, also that filter messed with the backfocus (ffd) (unless maybe that is because i did not use it correctly? I just screwed it in far enough it wouldnt effect the lens position, and put the lenses on like usual) which meant I had to unscrew the lens a big to get it to focus right.

Also, keep in mind that when using 35mm slr lenses, you might have trouble finding ones that give you a usable field of view. the multiplication factor for focal length will be nearly 6x. Also, you are working with 3.2^2 um pixels which i imagine is pretty darn fine even compared to the grain size that 35mm slr lenses are designed for. Youll be lucky to find an slr lens wider than 18mm thats not very expensive and slow. and on a 1/2" sensor, even that is a mild telephoto. also, there arent a ton of front-mount IR filters around, and the good one i found is the B+W #486 which i believe comes in 62mm (which i have) and 37mm or something like that. so no matter what you will probably be dealing with step-up/down attachments for the filter.
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Old February 17th, 2006, 08:01 AM   #77
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Noah, have you tried the Tiffen Hot Mirror? It comes in the common SLR thread of 52mm. The larger ones are really expensive, but the 52mm is only $65 at B&H.

http://www.bhphotovideo.com/bnh/cont...ughType=search

They have lots of other sizes.
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Old February 17th, 2006, 08:14 AM   #78
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i wasnt aware of those, that could be very useful considering they come in so many sizes. Any idea what the color response looks like on them? they just dont seem very well documented. I mean the way its written they seem to be intended as a supplement to a digital camera's normal IR filter, which might not mean they are suited as a primary IR filter?
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Old February 18th, 2006, 08:40 AM   #79
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If you can find a suitable triplet condenser you can condense the full field of view and light down to the chip.
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Old February 19th, 2006, 06:30 AM   #80
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35mm lenses

Noah -- wow, 6x multiplication for 35mm lenses. I think I originally thought: 35mm is about one-and-a-half inches across, the Sumix sensor is half-inch, so that's 3x. But of course, it's area you have to consider, so include another layer of 3x and you have 6x as you said. My widest 35mm lens is 28mm, which would become an equivalent 160mm -- perhaps ok if you're filming outside, but go into a normal size room and you'll be limited to shooting big close-ups all the time. This is no good. And I don't plan on even using all of the sensor so it gets worse. I always thought the resolution of 35mm lenses would be ok (very fine grain film can have grains of 2 microns), but in light of the excessively narrow field of view, resolution now seems achedemic. I was about to order the Pentax/C-mount adaptor but now I won't bother -- I'll be seriously looking at second-hand C-mount lenses (I don't have any any more, sold them many years ago with my 16mm gear). With small filter diameters though, I would need some serious stepping rings to get back up to 35mm size for access to SLR filters to solve the IR filter availability problem. This is annoying! Anyone know of any sources for big diameter jumps like these? Maybe two rings might bridge the gap?

With regard to how well an IR filter is blocking IR, I remember reading in a book called 'Hacking Digital Cameras' by Chick Cheng and Auri Rahimzadeh of a rough test. They said the IR block in digital still cameras is usually not total, and you find out how muich is getting through for a particular camera by using an IR-emitting TV or video remote control. With the remote about one foot from the lens, when you activate it you can see how much IR light flashes on the camera's LCD screen. If you were to do this with a camera that has had the IR filter removed, the IR flash from the remote would fill the frame. Don't know how useful this is...

Wayne -- I'd like to use 35mm SLR lenses if I could, but I don't know anything about condensors -- can you steer me to some website info on that?

Regards,
John.
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Old February 19th, 2006, 10:41 AM   #81
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Sorry John, been a long time. But if you have a look through he original adaptor threads they explore condensers for their projection screen adaptors, similar but in this case there is no screen and the condenser is one suitable to take the image from the lens. They link to a number of Optics science sites in those threads, that discuss things. The thing to watch out for (apart from bad ones that will give you various chromatic and lens aberrations) is that triplets generally are designed to correct for two primaries and either the IR or UV range, instead of three primaries. Such a triplet that corrects for the three primaries are usually ,ore expensive (hundreds even).

Now on the other side, one of the threads I posted on is an old one from virtually before the SLR adaptor thing took off. A guy on the short thread has a commercial Canon SLR lens adaptor for his XL1 that has a condenser instead of the normal hollow tube. He reports much brighter images. So it will be a thread from 2001-2003 that has XL1 and me on it, so an advanced search should find that, I was only on a couple of threads from those days.
rear screen adaptors
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Old February 20th, 2006, 04:09 AM   #82
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Wayne -- thanks for the Condensor info: I'll try and follow this up next week (I'm editing a short film at the moment).

Noah -- I rediscovered a company here in the UK which I dealt with many years ago called SRB Film Service. They sell branded filters and a huge range of stepping rings, including some they make themselves. They also make custom one-offs for you at a reasonable cost. Check out their website and if you can't see what you need email them your requirements -- they might be able to solve your IR filter attachment problem.

www.srbfilm.co.uk

Regards,
John.
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Old February 21st, 2006, 09:38 AM   #83
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Ok, remember how I said sumix's IR filter was kinda crappy? I just noticed their website had a new updated pdf on how to correctly use the IR filter. I thought, perhaps they are reading my posts and this is their indirect response to my complaints about their filter, i dont know. Anyway, it made me think maybe i just dont know how to use the filter correctly, so i set it up again, screwed it in and tried it out, and it wasnt as bad as i remembered. Granted, I still have problems with the backfocus distance, but I suppose i just need the right size washer to wedge behind the lens so it sits in the right place. Anyway, I tested the camera in a few configurations, with the rear filter sumix gave me, with that rear filter and the one that came with my computar lens (its not that good), and then with the sumix filter and my big b+w UV/IR filter. I will try to post shots to illustrate the difference, but basically its no good without a filter, much better but not amazing with the B+W filter, and then really not much worse with just the rear filter. Cosidering my difficulties with mounting the front filter, I will for now stick with the rear filter and try to find a way to adjust the backfocus. This will be a problem for my nice schneider lens since it doesnt actually fit in the c-mount all the way with the rear filter in. The schneider lens protrudes a lot past the cmount threads and that protrusion moves in and out relative to the threading when the lens is focused. maybe this will be ok with a spacer or maybe if i can figure out why the heck the last piece of glass in the schneider lens can be screwed out since it might fit if i just took out that part of the lens, but im a little afraid to mess with it.
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Old February 21st, 2006, 01:45 PM   #84
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That's good news. I'm looking forward to some new tests.
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Old February 23rd, 2006, 09:56 AM   #85
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I've been doing a few tests when i had free time. John's plans to play with Sumix's standard application inspired me to look into it a little more. It's not such a bad application. Saving directly to avi is still not really a worthwhile function because i tried it a few times and it recorded at a framerate about 1/4 whatever I had the camera running at at that time. Saving to RAM (which saves to available ram and dumps it to a .smx file), on the other hand, isnt so bad. Given you have enough ram (i had only enough for about 8sec of video), it maintains the framerate well without dropped frames and when converted to avi in the smxview app, it saves the effective framerate in the avi so it should play back realtime (although its unclear how accurate that is). it doesnt use the microsoft vcm to allow you to choose an avi codec, so you are stuck with uncompressed rgb which could then be converted to something more efficient.

I've been looking at things like gigabyte's i-ram or solidstate disk raids (not unlike P2) to remove disk access lagging. I wonder if saving to a ramdisk would be as efficient as saving directly to memory (memorystream in .net) or if my lag is a problem with the filestream.
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Old February 23rd, 2006, 09:15 PM   #86
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Not to much better (goes through the PCI bus) unless something is wrong, as the streaming to disk should be very streamlined by the hardware in parallel with your capture already, so slow up take speed of data by disk should not effect it (there is another possibility, if it is accessing memory a few bytes at a time to dribble it to disk that would severely break up memory performance and degrade overall performance, but I doubt in this day and age that this would happen).

So, yes it could be great, but if it is, something is not optimized in the software.

It is probably worth asking Sumix, and the manufacturer of the software, to help sort this problem out with you (streaming Bayer to disk and preview displaying at the same time). They will have the know it all expert programmers (if Sumix doesn't, the software manufacturer should). Maybe you could swing some work out of it,. They must be missing lots of sales because they don't ship their software with a friendly video capture application as standard (hardware needs 12 bit dual slope packing at minimum, head memory buffering, and even compression, which they were working on and direct to external disk caddy recording).

I just remembered something about these cameras that could affect performance, even though they have a set average data rate, unless the head has memory buffering the frame read out comes out in spurts around blanking and other operations.
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Old March 1st, 2006, 09:07 PM   #87
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Noah -- RE Schneider lens problem. I got some C-mount info from Schneider concerning their "older manual iris lenses" as they referred to them in the email. They list the 17mm Xenon f0.95 as a 2/3" format C-mount lens. They don't list a 1" C-mount at 17mm focal length (according to them for 1" it goes: 10mm, 16mm, 25mm, 50mm etc). When you say "the last peice of glass in the lens can be screwed out" I'm wondering if this is in fact a 2/3"-to-1" adaptor? If your lens-front IR blocker performs the same as the between-lens IR blocker, you might prefer to go back to using the lens-front one to avoid the Schneider rear element protruding into the between-lens blocker? The 17mm Xenon should have a filter thread diameter of 35.5mm (?). Looking at the range of stepping rings available from SRB Film service, you could make a light-tight connection for your lens-front IR filter using two stepping rings: 35.5mm to 49mm (special SRB ring) then 49mm to 62mm (standard ring). Standard rings cost between 4.90 - 5.50; special rings between 8.70 - 12.95 (I don't know what charges for overseas shipping).

John.
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Old March 3rd, 2006, 10:53 AM   #88
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Yeah it's definitely a 2/3" lens but im not sure why it would have a 1" adapter, and I tried removing that piece of glass only to find the image was not focusable or usable really. That element does seem to focus the image but I think if it is inteded for adapting with another format i dont think its a c-mount. anyway for now i will use other lenses and I need a spacer to increase the backfocus distance anyway which might fix the problem if it gives the scneider lens more clearance.

Sorry i wont be able to make many updates for at least a week, I'm off traveling in France a little.

As for ordering parts overseas, i havent heard good things about recieving packages in morocco (and i dont really even have my own mailing address there). so hopefully the rear ir filter will do what i need for the time being.
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Old March 4th, 2006, 06:50 PM   #89
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Noah -- as far as I understand it 1" is the standard form for C-mount, with 2/3" and 1/2" being smaller off-shoots. I believe the Sumix lens mount is 1", therefore if the 17mm Schneider lens is 2/3", then the 1" adaptor is definately needed for it to fit the camera. I was wondering though if it's the adaptor which projects further back (into the IR blocker) than a "native" 1" C-mount lens would? Buying second-hand C-mount lenses for box cameras can be problematic; I've found it difficult to get information on different brands (like Angenieux or Bausch and Lomb) to make good buying decisions. Perhaps I should start a thread to post what info I have (which isn't much), and this might encourage others with knowledge of these lenses to contribute and build a useful resource?

Enjoy France,
Regards,
John.
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Old March 5th, 2006, 07:10 AM   #90
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I wasnt aware c-mount came with any sensor/film format specifications. I have seen plenty of c-mount lenses for everything from 1/3" (although thats usually CS) to 16mm and 1". From what I understand c-mount only relates to a backfocus distance and a screw thread spec. I really dont think the single piece of glass in my schneider lens is a relay lens that converts its image coverage to allow the same field of view in 1" and 2/3" formats if thats what you mean. In general c-mount lenses just are rated 1/3,1/2,2/3,16mm,1" to tell you what the largest size sensor you can use without vignetting. All lenses intended for different sensor sizes still fit in the same c-mount, its just a matter of wether or not you are using the full coverage of the lens. Or are you referring to something else?
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