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You're definitely on the right track, now. When you say the "crop sensor without speedbooster receives less total light as the full frame sensor", you are correct in that the area of light that falls outside the sensor is cut off. Technically, that is light that wasn't received. But the confusion here comes from the idea that this somehow effects the part of the image that IS being exposed in the middle. In the original diagram, those two beams of light that hit the full frame and crop are the same intensity. Those pixels will be exposed the same amount, assuming the sensor tech are similar enough. It just won't see what is beyond the borders of the frame, as it is cropped out. The ISO and Aperture did not change. The entire image got cropped instead. But, the focal reducer condenses the light into a smaller point, thus making it more dense and intensifying it. Here's a diagram I threw together: Note that as the beams spread out away from the lens, they get larger and less intense because the photons scatter. And in the second example, the resulting image is just a cut out of the full frame one above it. The intensity of light that is hitting the sensor in the middle is the same intensity of light that is hitting the middle of the full frame one. The exposure is the same, the FOV is same, but now we are only seeing part of the image as the rest was discarded outside the viewable area. The problem is, if I want to see the entire subject (a camera in this case), I need to back up now. And by backing up, I am changing the distance between me and the subject, which changes the DOF calculation as well. But it has not changed the aperture of the lens, it has only changed how I might intend to use it. The DOF caculation is the same math as it always was (aperture size and distance to subject = DOF), saying that the aperture has now changed will really mess with the calculation of DOF as well as exposure. It is wrong IMO to say that. If someone bought a crop sensor and wondered why their DOF appears to be different, they never really understood DOF in the first place. But note the bottom example, the focal reducer aims the beams of light together towards a smaller point of light. As they do that, they are less scattered and more dense, and thereby more intense. The resulting image that hits those photosites is therefore brighter as a result. The resulting image is therefore the same framing and DOF as the original on a full frame, however now it has the added side effect of being at least a stop brighter as well! To all those saying the math in the video appears to be correct: It may appear to have worked in his example, but its like saying that 2 * 2 = 4, therefore * means addition. Yes, in that case, the answer is correct (2+2=4), but not for the correct reasons. When you try to apply the same math to 3 * 3, your answer won't be what you expected it to be (according to the incorrect assumption, you might say 3 * 3 = 6, however those that understand that * really means multiplication will be expecting the correct answer of 9). His math may appear to work, but his explanation is patently wrong for it!

Again, Canon sells EF lenses that are designed to go on any of their cameras, crop or not. That 50mm F/1.4 will have a different FOV on a full frame 5D, APS-C 7D, and entirely a different one on an APS-H 1DX. They don't list "FF equivalents" because it would be too $%#@! confusing to the consumer. They just sort of expect you to understand enough about this to make your own call. If you can't be bothered to figure out what 50mm looks like on an APS-C, then you shouldn't have bought one. And honestly, that's how it SHOULD be. The "FF equivalence" numbers have always bothered me, since I don't actually think in photography. My background is in video/cinema, and a "full frame" to me is super35mm film, a 1.5x crop compared to what everyone is talking about on the packaging. That being said, I understand why they do it. 12-35mm seems like a very limited and very wide range if you are coming from film photography. So what they are saying is "by the way, this covers the same range of that 24-70 range zoom that was considered standard on your old film camera". Oh, ok- this is what I need for a good walk around lens then. Yes, of course the DOF per-same-framing will be different, obviously- this is a "crop" sensor after all! You should have known that going into the camera system. No one is saying this will be the equivalent of a 24-70 f/2.8 on a FF, only that the range covered is what it is. The lens is still, in fact, a 2.8 aperture. It gathers as much light as a 2.8, and renders the same bokeh at the same distance to the subject. If you have to stand further away to get your shot in frame, that's your own problem to deal with. They shouldn't have to spell it out for you on every piece of packaging and marketing material. It sounds like the guy in that video wasn't aware of how this worked before he bought one, and felt cheated by the relative lack of DOF control compared to his FF. And is taking out that frustration in a misguided angry rant about how they are pulling a fast one on you (give me a break!).

Sure, I've taken a shot very similar to that by throwing a 135mm f/2.8 on a focal reducer.

I can't believe what I'm reading. People, this is really basic stuff- I'd expect anyone joining this site to at least have a basic understanding of how aperture and crop factors work. That's asinine, I'm sorry. You know why they don't call it an f/5.6? BECAUSE IT ISN'T AN f/5.6! It's an F/2.8! If it were an F/5.6, your image would come out extremely dark indoors. Your DOF might not be the equivalent of the same lens on a full frame, but the aperture is so much more than just DOF! I can't believe people are looking at it like that! Look, DOF is calculated on a mathematic level as the relation between the aperture and distance to the subject. This f/2.8 lens will have the SAME DOF as a full frame one or a smaller one based on that calculation, and together with the amount of light it gathers, calling it anything other than a 2.8 IS A DIRTY FILTHY LIE. If you have to go wider to get the subject in your shot, and therefore lose some of your shallow DOF, that's the mechanics of aperture-to-distance=DOF at play, and you should not have gone into owning a crop camera without understanding that. Remember, you can buy the same Canon EF lenses and use them on a FF 5D or a cropped Rebel t2i. Should they write that the F2.8 zoom is a 5.6 when using it on certain cameras? Why if you put it back on a full frame body? Why should we call it anything other than what it is? You guys are being ridiculous, I can't believe what I'm reading! That proposed system would make the world of photography a bloody nightmare for consumers, much more confusing that what we currently have! What we're trying to say is that the surface area of each pixel isn't bigger just because the sensor overall is. It doesn't have anything to do with the size of the entire sensor is. This has been proven with cameras that have smaller sensors or less megapixels on the same sized sensor. If you have one giant pixel, that one pixel will gather more light than a smaller one, true enough. But thankfully, that doesn't exist. A 16 megapixel MFT sensor actually has larger pixels than a 36mpix full frame one does. So explain to me how the larger sensor makes a difference there?

I don't even know where to begin. The science and real-world practical application both favor the explanation Andrew and I have been trying to give you. Forget about the physics behind it (which totally back up our explanation), I actually OWN speedboosters (focal reducers technically), crop sensors and full frame sensors. And I can tell you first hand what it does, or does not do. We're not wrong. But because I'm a sucker for a good internet argument, I'll play along a little more. Correct. On the full frame camera without a speedbooster, it is not condensed. On the crop sensor without a speedbooster, it is... wait for it... ALSO not condensed. Hurray, we agree! Um- who say what now? Yes, if the image circle is larger, the light is less intense. We're still in agreement! ...I think? Actually, that's not unlike a magnifying glass at all. Or a pair of glasses. Or any optical element at all. You might even say it is very similar, except facing the other direction. No lens can "add light" that doesn't exist. However, it can intensify it by condensing it. Just like bringing a flashlight closer to the wall makes the circle smaller and brighter, or the magnifying glass makes the sun light brighter and hotter. Is it making adding to the sunlight? Is the flashlight producing more photons? No. They are just not as scattered, and therefore brighter and more intense per surface area. The reason I can't take my projector and point it at the sky to get a giant movie on a cloud is because the image stretches out so far that almost all the illumination is lost. But conversely, gather all the light into a single point, and it becomes intensely bright. That's actually how a laser beam works. Hurray for science! True. But take that circle of light, pretend it is coming out of a flashlight. Make it smaller by optically reducing it. That smaller projection of light is brighter as a result. Light output is the same. The part of the image that hits the sensor is the same intensity as the light that misses it. Those pixels in the middle of a full frame camera get exposed the same amount as a cropped one. I can't explain this any better than that. True. Which means diddly squat for the pixels that DID get exposed. You're missing the point here- you're looking at the sensor size as a whole, which is silly. A digital image is merely a grid of single pixels, each one unaware of the others around it. The grid of a sensor is made up of photosites, each one responsible for roughly a pixel (oversimplification, but works for the purpose of this discussion). When a photosite is shown that bit of light it can see from the lens, it sends an electrical signal to the image processor which turns that information into a value of light. This happens regardless of how many OTHER photosites there are around it, however a larger one can collect more photons and render a more accurate color and exposure. That is why larger photosites (such as those usually found on larger sensors of the same megapixel count) can have less noise than smaller ones. But this isn't a function of the size of the sensor. Its a function of the density of photosites on that sensor. While a larger sensor has more room for big photosites, it isn't necessarily always the case (especially with 36Mpix full frame sensors!). The point is, the light that falls outside the sensor makes no impact on the light that exposes in the middle. On a full frame sensor, the light that falls on the middle photosites are the same intensity as those on a crop. It really makes no difference and it really is as simple as that. No. It is reclaiming the area that fell outside the sensor previously, but that is in regards to the field of view only. A happy side effect of condensing the light, however, is that it also becomes more intense. In fact, the math goes something like this: A full frame 50mm 1.8 on a Sony NEX speedbooster gives you the field of view of a full frame 50mm and DOF of a 1.8, but the light gathering ability of a F/1.2 I understand that's how you see it. Unfortunately, how you feel about it has very little impact on the science and actual real-world usage of the equipment. Case-in-point. Someone took a Sony A7 full frame sensor and stuck a NEX speedbooster on it for kicks. The image now takes up only the middle part of the frame and vignettes something fierce (edges are all black), and is brighter than it is without the speedbooster. That's just how this works. Care to elaborate as to which mathematics make sense to you? The smaller sensor has more noise because the photosites are smaller and therefore less light sensitive, the DOF changes because you need to place your subject farther away from the camera (DOF being a calculation of Aperture to distance). The things he is showing work for a completely different reason than he is saying they do. The larger sensor does not gather more light on account of being larger, the aperture does NOT change, following his math does NOT add up!

He said the "aperture changes", which is wrong. It does not. If it did, the exposure would as well. He wants to say that those manufacturers are somehow "lying to you" about the comparable lenses, that it should give comparable F-values as well. But the comparable f values would be far more misleading since they would pertain to light gathering ability! But that's just one thing he said. Most of his "points" are misguided, especially about how sensor size relates to light gathering ability. In fact, I have more problems with what he described than agreements. Please don't just accept this video at face value.

The noise being greater when you crop in on your A7R or GH2 is because you are now seeing more noisy pixels since they are larger. They were there before too, but you couldn't see them as the image processor was busy scaling down the image (and taking the noise with it) when they resample it to HD video. Even now, if you take a high ISO HD video and scale it down in post, you'll see less noise, as they get averaged together. THIS IS NO MERIT TO WHAT THIS GUY IS SAYING!

That's always what ISO meant on digital cameras, as I understand it. Every sensor has a sort of "native" exposure level, and ISO applies a gain (either analog or digital or both) to boost the signal or reduce it in some cases. I didn't need Tony to explain that, I learned that when I first starting playing with digital SLRs instead of film cameras. In order to standardize the values, ISO numbers were created and overseen by the International Organization for Standardization. So ISO 800 on one camera sensor would be approximately the same as ISO 800 on another, despite one applying a different amount of gain to reach that value. But it has nothing to do with the overall physical size of the sensor!

In case anyone TL;DR my explanation above, the 1st and 3rd have the same intesity of light hitting the sensor at a time (the guy in the video wants to say the cropped one does not. But that's because he's ignorant). But the middle one does not- it is brighter than the others because in reducing the image, the photons are also condensed (less scattered) which results in more intense light. Just like a flashlight or projector that is farther away / closer to a wall. The smaller the light gets, the more intense and vice versa.

Really?? ...I'm speechless.

I am shocked and appalled at how terrible the information in that video is (and I want my 37 min of my life back). What makes it worse is that he is actually presenting it with such arrogance and conviction, that people are buying into it! Karrim, let me take a moment to explain: If you take a picture on a 7D (APS-C crop) vs a 5D (Full Frame) with the same 50mm lens, the 7D only sees the center part of that lens. If you were to take that picture from the 5D and crop it inward 1.6x in post, it should look pretty much identical to the 7D's picture. Same bokeh, same DOF, same amount of light exposure. The difference is only that you are cropped inward so much that you might not be able to get your entire subject in the frame anymore. The aperture does not change on a crop sensor camera. PERIOD. However, you have to stand farther away from your subject to get what you want to fit inside the crop. Since DOF is a combination of aperture and distance, the DOF will change and become deeper as you step back more. But again, the aperture does not change! Only your distance has. A picture taken at the same distance will have the same DOF, and most importantly the same amount of light! The reason the manufacturers list "35mm equivalents" on their lenses is not at all misleading. Many photographers think in full frame FOVs, so they need to know that a 28mm is no longer a wide angle, but rather a medium one. The amount of light gathered does not change, the aperture is very much the same. But your composition is different, as you are standing farther away. F/2.8 at a particular distance to your subject will yield the same DOF no matter what size the sensor is. What Northup is saying is PATENTLY FALSE. As far as light gathering with a speed booster- imagine you have a flashlight, and shine it at a wall. As you get closer to the wall, the photons are less scattered, closer together, smaller and brighter. If you've ever tried to fry ants on a sidewalk with a magnifying glass, you know how a focal reducer can condense the light from the sun into a single spot intense enough to start a fire. So when using a speedbooster, you are actually gaining more light, technically more than a full frame camera with the same lens would as it is more condensed now. This is science, this is physics of light, and has been totally explained to death before. As an aside- his whole thing about smaller sensors having poor low light performance because they see less light overall. I'm with Andrew- total and complete bullocks. The size of the sensor overall has NOTHING to do with it, but rather the size of the photosites. The photosites are what make up the individual pixels for your image. The higher the megapixels, the more densely populated the sensor is and therefore the smaller each photosite. Smaller photosites gather less photons per exposure and therefore get noisier at similar ISO values to larger ones. But technically, you can have a small sensor with larger photosites than a larger one. The Sony A7S how shown what a difference smaller megapixel counts can do for a sensor in low light. Technically Panasonic can make a MFT sensor especially designed for low light by only making it 10 megapixels. Then we'd get stellar ISO performance compared to any 5D, despite sensor size. He keeps going on about how because the sensor is smaller than a full frame one, it can't see as much light and therefore the ISO needs to pump up the gain higher to reach the same exposure. Everytime he says that I want to shove my fist through the computer screen for being so arrogantly ignorant.

I am currently using a Nikon to EF adapter on my RJ EOS-to-M43. No problem at all. You have to make sure the adapter you are using is high quality though. One of my Nikon-EF adapters is a cheap one that has some give to it. On its own, it was good enough to use on a Canon body, but on another adapter, that give gets a little more exaggerated. You want the lenses to be tight. I'd buy from the source to make sure you are getting the most recent batch. http://www.rjcamera.com/ocart/ I got mine from there.

LOL Andy- The FD has been out since I first heard about the RJ booster! I bought one in FD and EOS, and actually used the FD version this morning on a shoot! Since my lenses are all FD, vintage Nikon or EOS, I now have them all boosted (Nikon on an EOS adapter). And the FD's get stepless aperture adjustment using the lever. I guess if I ever get any modern Nikon glass I'd need another adapter with the iris adjustment ring there too. Since I also own and use a Canon body, I mostly stick to EOS when it comes to modern glass (and stop down iris on EOS body before placing on adapter when necessary). Which brings me to answer this guy: The Nikon mount is the furthest flange distance of the popular lens types. That means the lens sits farther away from the film/sensor, and why you can almost universally mount a Nikon lens on any other body type (EOS, M4/3, etc) yet not vice versa. The BM focal reducer is a tight fit, as we've already seen. I'm willing to bet that they need all the distance they can get in order to fit that crazy reduction optic in there. EOS might be possible as it is only slightly closer, but Metabones has held out on the EOS mount until they get an active mount working as they did for the Sony adapters. Likely for the very reasons I mentioned above; without an EOS body available to change aperture, modern lenses are difficult to use on a passive dumb adapter. Once they start rolling those out, we might see an EOS adapter for the BM cameras with the same crazy optic, but I feel like anything shorter than that is too tight of a squeeze!

Wasn't there discussion somewhere about the rolling shutter on the A7s making it more-or-less a limited use camera? I can't remember where I saw it, I could have sworn it was this forum.

All in the hands of the user. It can look pretty great if used properly. I'm not sure why that short in the OP came out the way it did. Perhaps Nick was playing a big prank on all of us? I didn't care for the image either, but I know Nick is capable of better.

Except that at 720p the camera samples even lower resolution than it does when set to 1080. More aliasing and more moire.

Its strange to me that people are still confused about what a speedbooster does or does not do. :P I find it strange that you are comparing this to a native Panasonic micro4/3 lens. They tend to be super sharp and clinical, often to a fault- they lack character and feel too much like video at times. Those of us using adapted glass are doing so because we prefer the look compared to native clinical variations. There are few things as cinematic looking as a vintage set of primes actually designed for film- but sometimes they come with uncontrollable side effects because of the less-than-perfect coatings. Here's the thing I feel you are missing: Those lenses would display chromatic abberation / fringing with or without a speedbooster. You imply that the speedbooster is causing this somehow, but I believe that is incorrect. Its often just a quality of the lens- the focal reducer does not make them WORSE at all- in fact, sometimes it actually makes them BETTER. In my experience, since the optics are reduced, the fringing and imperfections get smaller as well. Not to mention the reducer has some coatings of its own that help reduce reflection and glare that cause uncontrolled flaring in the first place. The bottom line is that my vintage lenses actually are IMPROVED by throwing it on a speedbooster/lens turbo/etc versus on a straight up adapter! Now, if you wanted to mount a modern FF clinical looking lens that doesn't have any flaring/etc on a speedbooster, that might give the effect you apparently are looking for. I sounds like you've seen some tests of character lenses on a reducer and have decided to compare it to a native clinical lens. That's apples and oranges, my friend. Um... maybe? Technically a photon is a quantum, but I'm not sure what that adds to my explanation. I'm just saying the light is gathering together and therefore being intensified. Much like holding a flashlight to the wall and getting closer to it, the image circle gets smaller and more intense because the light isn't spreading out as much. More light, smaller circle, more FOV and shallower DOF. WHY ARE WE STILL DEBATING THIS? THE CONCEPT WAS EXPLAINED TO DEATH ALL OVER THE INTERNET OVER A YEAR AGO! I feel like anyone interested in this concept would have understood it at this point. Right. Didn't we have this discussion a year ago? Its like the DSLR video revolution all over again... Yes, people are using "still cameras" for video now. You didn't know that? Ok. Can we fast forward this part of the conversation to get to the news already? KEEP UP PEOPLE! There are some interesting tests all over the internet. The first knock offs were pretty terrible (Fotodiox Light Cannon, for example), softening the image all over the place. They've gotten better, the general consensus is that the Speedboosters are the best (consistently sharp and flare free), and there's an apparent toss up between the RJ and Mitakon lens turbo models (My research pointed to the RJ being sharper in corners and less flaring than the Mitakon, Andy's research concluded the opposite, so I suppose it is arguable), followed by all the cheaper knock offs in similar flavors. The cheap knock offs are a crap shoot as far as quality of the optics. Whichever you buy, make sure it is the latest version and batch, because they have improved the coatings from the original runs.

Sure. In 720p. :P

Or the RJ version, both have EOS to M4/3, but no electronics. For that we'll have to wait for the Metabones. Meanwhile, I have Samyang glass and adapted vintage Nikon F-mount lenses running through the EOS adapter like a champ. Occasionally I'll use a native EOS lens and stop it down with an EOS body first. Not the most convenient way to go about it, but it's all we have at the moment.

Again, you've clearly missed the point of the focal reducer concept. I feel like the author of this comic right now: https://xkcd.com/1053/ You're one of today's lucky 10,000! Go back and read all the reviews of the initial speedbooster when it came out. It really does effectively make your sensor act like it was larger. Everyone agrees on this, it isn't up for debate anymore. I know a guy who actually sold his 5D to get a Sony FS100 and use the same lenses on the speed booster. Same DOF and bokeh, but due to condensed photons, it also gets brighter (a 28 f/2.8, for example, renders the same FOV and DOF as it would on a full frame, but gets the amount of light gathering of f/2.0, effectively allowing you to turn down the ISO for the same exposure and same exact looking FOV and DOF). In contrast, if you are using a m4/3 speedbooster, you aren't getting the full effect because you are still at a crop compared to full frame. Its closer to full frame - 0.7x closer, to be more precise, effectively giving you a 1.4x crop instead of the 2.0 you started with. That's a bit wider than your average Canon APS-C camera, but still not quite photographic FF. Its somewhere in between. You CAN get the FF look with the NEX adapter, since it starts at APS-C already, or with more focal reduction, which is what Andrew was telling us with this story.

I use the shrigg jig from Indiesystem. Its designed to fit a GH2 so its not too big (and fits with the camera mounted inside my gear bag) and I like the mounting points on the sides as well as top and bottom. Only catch is the battery door doesn't line up, so you have to actually REMOVE the camera to change memory cards (annoying). Otherwise, its a great and inexpensive cage that isn't too big.

FALSE! You sir, have missed the beauty of the focal reducer concept! It shrinks the entire image circle of light that was intended to cover a full frame sensor, giving you the similar FOV and DOF! You see what a sensor of that size would see, plus an extra light gathering stop because the photons are now condensed. Lenses become wider AND faster (and in many cases sharper because the imperfections are shrunk as well). It sounds like science fiction, but its just science! I'm speaking from personal experience with these as well as from a physics perspective, THE DOF DOES IN FACT CHANGE.

Cool- let me know what you think if/when you get to compare them. Again, I'm just basing this off of what I've heard and read from other users.

Andy- None of these adapters have an iris (as in, the fake aperture blades that some EOS adapters have adopted to let you change f-stop on a Canon lens). However some of them have a lever to control the len's iris where supported. You are correct, however: it appears that the Mitakon version does not. Which seems like a severe downside in my opinion! I love having stepless aperture changes and the ability to use modern adapted glass. The RJ FD and Nikon adapters do. I've seen those tests from Mr. Caldwell, they have been discussed to death on other forums (lets just say that a certain Vitaliy has some pretty harsh opinions of Brian's test being biased). I do find it very interesting that Caldwell's test is one of the only ones that seem to suggest that the RJ adapter is inferior. Most of them report the RJ being of higher optical quality, especially regarding edge sharpness (where the Mitakon really falls apart on every test I've seen except for Caldwell's). Also understand that RJ's adapters had an update, as I understand it. Perhaps he was testing the initial batch which has since been fixed. Either way, I'm just reporting what I've researched and came to a totally different conclusion than you did. As far as the name is concerned- I've seen no less than three products referred to as a "Lens Turbo", including RJ's. Not sure if it is an officially registered name to anyone, but I could be wrong. :)

Funny, if you search around the internet for those who've used both, the RJ lens turbo is generally said to be the more expensive and sharper version. The mitakon is a branded version of the no-name Chinese adapters that are all over ebay. I've been following this for a while, and trying to figure out if the extra sharpness on the RJ is worth a few extra bucks or if it is largely unnoticeable in video. You are under the assumption that the opposite is true, it seems. The new RJ versions have largely cured it unless you are going super wide. I had a conversation with RJ (he's super nice and very responsive, a great guy to talk tech with and knows his stuff), and he told me that with the latest batch, the blue dot only appears with super wides like the tokina 11-16. Some of the Mitakons may have repaired this as well, but it will depend on which batch you get (ebay is a mixed bag from different runs, according to tests in other forums). Wrong again, unless the Mitakon is again inferior to the RJ version: The EOS version does not have aperture control (as any simple adapter wouldn't, it is electronically controlled). But the FD and Nikon version have that open/close blades switch for manual adjustment that are common on these adapters.