Leaderboard

In the end, we never stop talking about these suckers across multiple threads, so I'm gonna try to compile as much information as I can into this one. As in most cases, diopters are cheaper than anamorphics, I ended up with a lot of them, from multiple brands and multiple performances. The key was never go where everyone else is trying to find. Got the classics too, but that was luck. Anyway, let's go to the undeniable favorite: Tokina +0.4 Achromatic diopter. My only complain about it is: why aren't you bigger?! My first lens was the LA7200 and I took quite a while to find the 105mm. The next lenses all had different thread sizes. I could filter the Hypergonar on 77mm or 86mm, the Kowa with 72mm, Sankor 72mm too, Isco 54 at 95mm or 86mm and had a plan of an alternative 86mm front for the Lomo Squarefront, which didn't go through. Anyway, if I started to look for all these sizes of diopters, I'd go broke. My salvation were the Series 9 filters. If someone isn't familiar with these, they come as unthreaded glass, that you put into an adapter that can range between 67mm and 86mm. That pretty much covers all lenses. I got adapters for 72, 77 and 86. The glass itself has around 83mm diameter. Tiffen Series 9 filters are not in production anymore, so you can pick them off cheap ($1-10), even though they're not so common. The adapters are a bit harder to find. After that, I went crazy on other brands as they showed up with decent sizes. Got 77mm Spiratones +0.5 and +0.25 for $6, 86mm +0.6 Fujinon, 72mm +1.25 Fujinon, 95mm +0.25 Pentax (for the 135-600mm Pentax Zoom), 82mm +0.75 Canon (1300H), etc, all very cheap. Some of them are real heavy, and I don't know if they're achromatics or single elements. The advantage of the bigger ones is, less vignetting, even when you go wide, and, the sharpness is increased, since you don't get corner areas. Finally, I found a couple 4.5" ones (around 114mm), that require special adapters, like Series 9. These adapters are impossible to find! I'm making a couple myself, as I trust threads more than tape. :P EDIT Dec 07, 2014 Why Look for Low Powered Diopters There's a common question going around, of WHY fraction diopters are better than full numbers, so I'm addressing that here too. Rich has a good explanation too >here. As you can see below in the math section, the numbers correspond to certain maximum and minimum focus distances. When it comes to anamorphic lenses, what is the most common minimum focus distance? Something between 1.5m and 2m (or 5 to 7 feet, imperial scale). Iscoramas have 2m minimum focus. Kowas, Sankors and most dual focus projector lenses are set to 1.5m minimum focus. For most shots, this distance is greater than the distance you want to put between the camera and your subject, which leads to being unable to focus properly - also, it's a pretty messed up distance for working indoors. What a +0.4 or +0.5 diopter does is turn this "near 2m minimum focus distance" into "near 2m MAXIMUM focus distance" (see math below, seriously), allowing you to frame and shoot freely indoors and much closer to your subjects. If you want extreme close ups, then you need to have stronger diopters, but a +0.5 is a key tool for "standard" shots. Achromats are also better, but they have their own explanation below too. Focus and Anamorphic Compression Another thing that relates directly to diopters is the lens compression. Most of our 1.5x or 2x stretch lenses only have that proportion when focused to infinity. Things change when you twist the focus ring. As you get closer to minimum focus, the less compression you have. 2x lenses tend to go towards 1.7x or 1.8x, Iscoramas get very close to 1.3x. When unsqueezing your footage, this compression disparity can make shots look different from the rest of the footage, as if it was shot with a different lens. In a technical level, it really was a different optical path. Using diopters you get rid of using the shorter distances on your focus ring and keep your compression constant throughout the shots. DISCLAIMER: I don't know how this relates to baby anamorphics, and this CERTAINLY does not affect focus through lenses since you don't change the distance between the anamorphic elements. //EDIT. Strength measuring: Fujinon: The first number is their maximum focus distance, the second number is the thread size. For example, a 16086 reaches 160cm at infinity (+0.6) and has 86mm thread. 190101, 190cm at infinity focus, 101mm thread. Canon: The newest series (250D and 500D) measures in millimeters their maximum distance. 250mm equals +4 and 500mm equals +2. The "D" stands for Double element. The older ones use the same measuring, 1300H = 1300mm, +0.75. There's also a 900H, 105mm, which is a like +1.1. When nothing is marked on it, good luck with testing the thing. It's usually not hard, but most of them have information lying around the web. Thread size: As well as regular threads, some are marked with a C after the number (mostly 86C, 95C and 105C), that means the thread on this filter is coarse, 1mm pitch. Our regular (fine) threads have .75mm pitch. There are adapters for these too, like the one below, from 86mm fine to 86C. http://www.ebay.com/itm/350325079425 Minimum and Maximum focus distance: Just realized that I haven't explained the math relating diopter strength and maximum focus range! Since most anamorphics perform better when focused closer to infinity, a diopter gives great help in "faking" it optically. A close up filter "sets" infinity just a couple meters/feet away, so anything BEYOND that certain point will be IMPOSSIBLE to focus. Of course, this will NOT follow the lens' focus marks. Infinity on the lens now equals the diopter maximum focus distance. Now, the numbers: S = diopter strength (+0.5, +0.6, +1, +2, etc) MaxFm = maximum focus distânce, measured here in METERS MaxFm = 1 / (S) Ha! I bet you expected something waaaay more complex, right? Some examples are never bad, so let's get to it. I'll use +0.5, +1.25 and +2 as sample strengths. MaxFm = 1/(0.5) = 1/(1/2) = 1 x 2/1 = 2 meters MaxFm = 1/(1.25) = 1/(5/4) = 1 x 4/5 = 0.8 meters MaxFm = 1/(2) = 1/2 = 0.5 meters If you live in a country where imperial scale prevails over the metric system, you just gotta do a quick fix to the expression. S = diopter strength (+0.5, +0.6, +1, +2, etc) MaxFf = maximum focus distânce, measured here in FEET MaxFf = (3.3 / S) Same examples from above, now in feet MaxFf = 3.3/(0.5) = 1/(1/2) = 3.3 x 2/1 = 6.6 feet MaxFf = 3.3/(1.25) = 1/(5/4) = 3.3 x 4/5 = 2.6 feet MaxFf = 3.3/(2) = 3.3/2 = 1.6 feet Regarding minimum focus distance, I'd say anything closer than half maximum focus distance is gonna look pretty bad already. With high power close ups (+2 and up), I'd say anything closer than 3/4 of your maximum focus distance is gonna be pretty bad already. Of course, this "minimum focus distance" image quality has A LOT of influence from the anamorphic. Also, achromatic diopters will improve almost everything you could imagine. Since I've just mentioned them, here's a list of achromatic diopters, with their strength, manufacturer, price range, etc. http://fuzzcraft.com/achromats.html Price range: Just for checking, here is a list of the most common lenses and their outgoing price. Tokina +0.5 72mm - $150 Kenko +0.5 72mm - $90 Tokina +0.4 72mm Achromatic - $350 Kenko +0.3 105mm - $350 Canon +2 72mm Achromatic - $100 Sigma +1.6 62mm Achromatic - $20 Angenieux +0.25 82mm - $330 Kinoptik +1 82mm Achromatic - $530 Foton-A +1 or +1.25 - $900 (GONE!) Tiffen +0.5 to +2 138mm - $50 and up Tiffen +0.5 to +5 Series 9 - $1-50 Tiffen/Kodak Series 9 Adapters - $20-40 Tiffen +0.5 to +2 4.5" - $10-50 (RARE)

not really that amazing i looked at this post then checked my spam folder : )

And it is done!        

  A very elegant solution.

I've just ordered this lens: http://www.surplusshed.com/pages/item/l3943.html I'm hoping that a 1 inch format lens should be fine for BMPC. I figured that at around £35.00 it's worth a punt for a 35mm equivalent.

Tim, I'd avoid this one, since is too small for the front of the LA7200, and this bayonet mounting is a bit confusing. It doesn't work in regular filter threads, you'd have to adapt.   Try this one, it's cheaper, and way bigger http://www.ebay.com/itm/190827528672 or http://www.ebay.com/itm/400440410462

Hello everyone! I am happy to see you debating the concept here.   I just wanted to answer a few of your questions:   The reason why I went for Pol-Vari ND was that from the beginning I knew that an electronicly controlable aperture was not my field. So with e.g. a ND 0.3-0.6-1.2 variant that leaves you final adjusting your exposure at daytime with shutterspeed, since your ISO likely is set to the lowest possible. I didn't think that was flexible enough, and that would also mean compromising the shutterspeed which I wanted to be able to leave at 180 degrees. Plus - by always having that thought of "which one of those parameters do I want change know" you mind will be less present on the situation where you're at. And sure - all Vari-ND:s have flaws that can never be fully fixed, but I felt it was the best choice for people working fast.   Regarding color shifting (remember - all Pol-Vari inevitably suffers from this) please check out the HolyManta VND color cast test: https://vimeo.com/64344672   I'll try to stick around here to answer more question, otherwise send me a mail.

There are some serious amounts of (des)information in this thread... Both regarding how chroma subsampling schemes are laid out, and how normal Bayer based sensors record video images in consumer-grade DSLR devices.   Now, in order from capture to recording:   Each manufacturer (and also separate models of cameras!) have their own way to read a sensor to create an initial image to "build" the video image from. *Some cameras line-skip, since that's a very easy (and bandwidth-economically good) way to read a sensor FAST. Unfortunately, this gives lots of noise (much of the actual recorded information on the sensor is just thrown out unused) and lots of orientation dependent aliasing. This exact aliasing depends on how the manufacturer choses to scale the image from the original resolution of the sensor. *Some cameras have other means of restricting the amount of pixels/second it has to read. Those can include true binning, patterned subsampling and many other schemes. Most of those schemes can also be reverse-engineered if you know what you're doing.   Almost ALL consumer-oriented cameras do after this initial sifting of information. Most of the quality loss except for the compression and chroma sub-sampling occurs here! At the second leg in the image pipeline you have a complete RGB 4-4-4 image at some (smaller) pixel scale. This depends on the original resolution of the sensor vs the subsampling method chosen. But it's often around 1200-1350 pixels on the X-axis and 800-950 pixels on the Y-axis.   Those are true 4-4-4 RGB images! But they aren't true HD resolution... Which is why most DSLR images are quite a lot softer and less detailed than true 1080p video.   The video compression engine accepts RGB as input, doing YCbCr(YUV) transform before sending the image stream to the encoder is just a big waste of effort. In the encoder input, the 4-4-4 RGB image is subsampled into 1920x1080 Y-channel data and [some] resolution CbCr(UV) data before it's sent in to the compression encoding.   So, no - you don't need an area of 4x4 Bayer-coded pixels to make 4-4-4 video. You need 2x2 pixels to get full-resolution images for ALL CHANNELS, the definition of 4-4-4. If you do a Bayer interpolation before coding, you only need ONE pixel to get 4-4-4 video... See Nikon D4 1:1 crop video mode next.   One instance is the 1:1 pixel crop video you can get from a Nikon D4. The video image in that mode is made from a 1920x1080 crop from the central part of the sensor. That image needs to be Bayer-interpolated before it's a full RGB image, but at least it's a full-res image. That's why it's so much better than the large modes in that camera - the large crop modes use line-skipping and lower actual image resolution. The loss from that is much bigger than the loss from having to do a Bayer interpolation.   If you want to read more about chroma subsampling and the exact layouts used, I'd recommend this: http://dougkerr.net/pumpkin/articles/Subsampling.pdf

A few additonal comments some specific to Nikon and Canon DSLRs. raw is 'single channel' 12 or 14bit data in linear light values and has no color gamut, ie: rec709, prophoto, ACES defined. So no skewing of values by gamma encoding and no restricted color gamut other than limitations of the camera hardware. Both those choices become user choices in the raw development process. Canons Digic processor handles this, it takes in the raw, does the raw development process like demosaic, line skipping (in pre mk3 models), applies various processing steps including camera response curve, picture style and outputs 4:2:2 YCC (lets leave analog YUV in the gutter). Not RGB. The 4:2:2 is aimed for the LCD display which takes YCC input. Canon added a h264 encoder chip to its line of cameras and tapped into that 4:2:2 and sent a feed to the h264 encoder and jpg image writer. The 4:2:2 YCC has been calculated slightly differently to rec709 mentioned above, for many models of Nikon, Canon and GH3 MOVs, the luma chroma mix is based on BT601 luma coeffs ie: color matrix, uses a rec709 transfer curve to go to gamma encoded YCC rather than linear light and declares rec709 color primaries in order to define the color gamut. The Nikon uses a BT470 transfer curve not rec709. The result is not rec709 4:2:2 in camera but JFIF, think jpg, chroma is normalized over the full 8bit range mixed with full range luma. That normalized 4:2:2 gets fed to the LCD screen and h264 encoder and soon for 5D MKIII hdmi out but to rec709 no doubt. YCC 4:4:4 and RGB are not interchangable in dicussion but belong to two different color models and need handling correctly accordingly especially getting luma coeffs and luma range correct in the conversion to RGB for display, otherwise undue clipping of channels will occur, artifacts created and wrong colors, pinks skewed toward orange blues to green. Great info CD.

Let's try.       For each photosite in a bayer pattern, you capture luminosity for a certain region of the spectrum. But this is not luminosity as we see human see it. (Think putting a red filter on a b&w film). So for each block of 4 photosite (RGGB) they extrapolate some luminosity as if it was white light using (in REC 709) this formula Y = 0.2126 R + 0.7152 G + 0.0722 B (http://en.wikipedia.org/wiki/Luma_%28video%29). So the luminosity you captured is not perfect.   What you have captured contain 4 samples of color information.   So for the resultant 4 pixels, we have 4 luma info (aproximated) and 4 chroma info.   If we wanted to capture a real 4:4:4 RGB we would need for a block of 4 pixels - 4 greens, 4 red, 4 blue. As each one provide it's part of the spectrum in luminosity, we have 12 samples of luminosity (remember 4 luma for Bayer). (If we converted to 4:4:4 YUV, 4 samples of luma, 8 of chroma)   Now let's go from 4:4:4 to 4:2:2. To go to 4:2:2, we have to convert to YCbCr. For both chroma channel we discard half the information. So we get 4 samples of luma and 4 samples of chroma.   4:2:2 YCbCr is 8 samples of combined chroma/luma. Bayer is 4 samples. So Bayer is half as good as 4:2:2.     So why 4:2:2 from the uncompressed hdmi out is less good than Raw from the BMCC ? Because first the 4:2:2 you get is from a Bayer Pattern, so you already converted all the data. But you mainly processed the Raw Data to some preformated preset from Nikon, Arri, Sony or Hasselblad - it is not as automatic - far from the dumbest guy using a Raw Converter.   So now is 4:2:2 better than Bayer. Yes. Much better. I would no convert any of my work back to a bayer encoded file. It is that bad.   Look at what it is without any demosaicing :       What would be the best output in my opinion that every camera should have ? Not HDMI of SDI, but a digital raw output protocol, somthing like S/PDIF or AES EBU for audio where you output RAW and you do what you want with it from your external recorder. First, about the same bandwidth for a 16bit RAW Bayer than a 8bit 4:2:2 uncompressed. You'll also be able to convert on the fly using some standard algorithm or proprietary (think Fujifilm). And to whatever codec you need...