Last time I mentioned focal reducers and I thought I would go over them in detail this time round. Focal reducers are in essence the opposite of a tele-converter. Rather than increasing the effective focal length of a lens they decrease the effective focal length of the lens. How do they work and are they any good? Let’s find out.

First I want to start with tele-converters as they have been around in photography much longer. These are often referred to as “doublers” because the most common ones effectively doubled the focal length. I call it ‘effective’ because the lens focal length does not physically change. With a tele-converter the way the focal length is “doubled” is by having a lens assembly that crops away 75% of the image and then projects the remaining 25% in the center across the entire sensor or film. Because 75% is cropped away, the remaining amount of light is only 1/4 as great and so two stops of additional exposure is required. With the less common 1.4x units only half the image area is cropped away and thus only 1 stop of additional exposure is required. Remember that the image area is two-dimensional so when cropping 1/2 of each dimension you actually remove 3/4 of the image area. As an example, the image area seen by a 100mm lens is only 1/4 as much area as a 50mm lens. Why? Because both dimensions tighten up by 1/2. An 8 foot by 12 foot sign that fills the image with a 50mm lens taken from the exact same spot with a 100mm lens will only show 4 foot by 6 foot. The area seen by the 50mm lens is 96 square feet the area seen by the 100mm lens is 24 square feet. The tele-converter optics take that 25% or 50% image area (2x vs 1.4x) and spread it out over the entire film/sensor area to create the effective doubling or 1.4x focal length. The lens is producing enough light to fill a full frame but the tele-converter is focusing on a small cropped portion and then optically spreading it out to cover the full frame. This is why there is an effective loss of two stops with a doubler and 1 stop with a 1.4x. It’s all math.

Canon M5 with Leica R 90/2.8 and 0.72x FR ISO 400 1/1250 second @ f/2.8 (effective 104mm f/2.0)

Focal reducers are much newer to photography, but have been around the astronomy scene for decades. These devices are designed to take light that is “wasted” and squeeze it onto a smaller area. When telescopes started getting really long on focal length, astronomers found that viewing large more faint objects became nearly impossible. The focal reducers were designed to effectively make their scope a wide field unit with brighter images. These reducers became a coveted advantage in astro-photography by cutting exposure times dramatically.

In photography we now have these modern mirrorless cameras that can accept a wide variety of lenses due to their extremely shallow flange to sensor distance. This means lenses designed to cover larger formats can be used but the sensor is cropping away much of the image. In the case of a micro four thirds camera with a full frame lens mounted, it is the same 75% that is unused. A 50mm f/2.0 lens on a 4/3 body will only see the image area in the center making it shoot like a 100mm f/2.0. A focal reducer aims to capture some or all of the wasted light that would have filled the 35mm full frame sensor. The optics in the focal reducer gather that light and focus it onto the smaller sensor. If we were to take a 0.5x focal reducer and use a FF lens on a MFT camera we would gain 2 stops of effective speed as we can utilize all the lens light gathering ability and focus it onto the smaller sensor. The focal reducer at 0.5x makes the lens an effective 25mm f/1.0. A 25mm lens on MFT shoots like a 50mm on full frame. Metabones does make a 0.5x unit for 35mm/FF to MFT!

The focal reducer is essentially the opposite of the tele-converter. The tele-converter takes a small portion of the light coming through the lens and spreads it out over a larger area thus “thinning” the light but granting a tele-photo effect. The focal reducer removes all or part of the cropping effect of smaller sensor cameras by taking the larger amount of light and forcing it onto the smaller sensor. One key difference is that a tele-converter does not require a lens for a larger format camera. A focal reducer does. If you were to attach a focal reducer to a full frame camera and use a full frame lens with it you would get severe vignetting.

The main players in focal reducers are Metabones, a Canadian company that uses American optics to produce amazing results, and Zhongyi Optical from China offering a solid performance at a more reasonable price. Metabones markets their focal reducers as “Speed Booster” while Zhongyi calls theirs, “Lens Turbo.” Neither of these two companies offer a unit that will mount to a Canon M body so I bought one from a lesser known Chinese company. I got a Canon EF to EF-M focal reducer in 0.72x for less than $100 and have had surprisingly good results. In fact if either Zhongyi or Metabones will make an EF-EF-M unit, I’ll buy it.

Canon M5 50mm Zeiss Pancolar f/2 with 0.72x FR (effective 36mm FF or 58mm on APS/c) focus @2 feet. ISO 400, 1/80 second @ f/2 (effective 1.4)

Metabones units have electronics that pass lens information through to the camera body. For Canon EF to Sony E they have a software chip to convert Canon language into Sony. This allows for full autofocus in some cases. The Lens Turbos do not have electronic pass through. So until Metabones gives me an option to buy their product, I am relegated to this cheap unit. You here me Metabones? Come on the flange distance is identical to Sony and you don’t need the cpu converter! If you shoot Sony Metabones makes all kinds of these adapters. If I had a Sony I would get the EF-Sony E mount model as it allows full pass through of Canon EXIF data and autofocus although the focus is sluggish due to the electronic conversion chip. Canon EF mount is readily adaptable to a wide variety of other lenses like Nikon, Pentx K, M42, Yashica/Contax and more. If you have a FF Sony A7 camera you need to shoot in APS/C crop mode when using the Metabones or other focal reducers. Remember the focal reducer takes the light from full frame and squeezes it onto a smaller sensor.

Shockingly, the low-priced product performs very well. The only issue I have found, which was disclosed by the manufacturer, is an occasional purple/blue ghost flare under extreme lighting conditions. The contrast, color, and sharpness all appear to be excellent. I can’t wait for Zhongyi or Metabones to pull their heads out of their asses and build an EF to EF-M version. For the record I bought my cheap FR on ebay for $79 from China, took a couple of weeks to arrive. Mine is a 0.72x focal reducer that reduces exposure time by one stop. So the 50mm f/2 from the example above becomes an effective 36mm f/1.4. A 36mm lens on my Canon M5 shoots like a 58mm would on FF.

Canon 5D Mk III Zeiss 58mm f/2 Biotar focused at @2 feet ISO 400, 1/30 second @ f/2

It is important to understand that the lens you shoot with either a tele-converter or focal reducer is still the same focal length and aperture. Tele-converters and focal reducers change the angle of view, not the actual focal length and aperture. For example the 50mm f/2.0 lens remains a 50mm f/2.0 lens when using either the FR or TC. The depth of field doesn’t change nor does the characteristics of the original lens. The optics inserted behind the lens simply modify what the sensor sees. The use of light is what changes. With a TC we are using less of the available light gathering of the primary lens to achieve a telephoto effect and with the FR we are using more of the light gathering ability of the lens to get a wider angle lens and more light.

So for the math people here is how it works. F-stop is a simple ratio equation. The focal length divided by the aperture in like terms. A 50mm f/2.0 has an aperture of 25mm. When a 2x TC is used we end up with an effective 100mm f/4 reverse the math 100/4 = 25. Remember the TC or FR doesn’t change the physical-mechanical primary lens it still has 25mm of aperture. With the FR using the above example of a 0.5x FR on the same 50mm f/2.0 we end up with an effective 25mm f/1.0 and that is easy math 25/1 = 25, again, the physical max aperture doesn’t change, it is always gonna be 25mm on that 50/2.0. With the doubler the optics are spreading a small bit of light out over the whole sensor. With the FR the optics are taking a full frame light source and concentrating it onto a smaller sensor which increases the intensity of the light thus improving exposure time and effective f-stop. The math pans out.

For the record we are talking about F-stop not T-stop so F-stop is just pure basic math where as T-stop values are actual measured light transmission taking all the variables like air-glass surfaces, multi-coating, et al. You need to have a post-grad degree in physics to calculate the pure math on all those T-stop variables. T-stop is another post, today just F-stops 🙂

Generally speaking, it is harder to maintain image quality with a tele-converter than it is with a focal reducer. This is especially true with modern digital sensors that prefer MORE light than less light. High end manufacturers TC units are very expensive and this is because they have to overcome the tendency of TCs to impair image quality. The moral here is NEVER buy a cheap tele-converter! The more pixel dense your sensor, the less it will like a TC.

Canon M5 with Carl Zeiss 180/2.8 and 0.72x FR ISO 400 1/800 second @ f/2.8 (effective 207mm f/2.0)

Since the focal reducer is concentrating more light on the sensor, they tend to maintain and in some cases improve overall resolution by giving the sensor what it really wants… more light! This may be why I have gotten respectable results from a cheap FR. Smaller sensor cameras are generally more pixel dense. My Canon 5d Mk III has 22.6 MP on a 24x36mm sensor. That works out to 160 pixels per millimeter. My EOS M5 has a 24 MP sensor on 22.2 x 14.8mm sensor. That works out to 270 pixels per millimeter. The smaller sensor is far more pixel dense. It likes more light. (this phenomenon is why phone cameras look good outside but suck in low light) I wrote about sensors here.

Below are 5 sample images. I have a set of Tamron Adaptall tele-converters, both the 2x and 1.4x. I only have 3 compatible lenses for the TC units a Tamron SP 17mm f3.5, Tamron 28mm f/2.5 and Tamron SP 500mm f/8. The 500 was the logical choice, but it is a reflex lens fixed at f/8. It is a good reflex lens but in general these cat lenses are not super sharp. But I was able to take all the variable shots from the same vantage point on both the 5D Mk III and M5 with the lens. I made the same blanket adjustments on all the images in Lightroom except the 5D shots have a slight color temperature shift to compensate for the different white balance on that body. The captions under each photo explain the lens-camera-adapter combo and the effective values include the TC or FR and crop sensor value. The shot taken with the 500mm lens and the 1.4x TC on the M5 is an effective 1120mm lens in 35mm/FF terms. here’s the math. 500mm x 1.4x TC = 700mm. 700mm x 1.6 crop factor = 1120mm. My effective values are converted into 35mm/FF equivalents.

Look at the depth of field; it really doesn’t change at all in any of the photos. The lens has a fixed aperture and the focus distance is identical. In theory the depth of field should be much more shallow on the longer focal length shots. It isn’t, because the lens is what it is, a 500mm f/8. That is why the focal lengths with the tele-converter or focal reducer are “effective” focal lengths. The only thing that changes using these devices is the angle of view.

In short, I like focal reducers very much. I will buy a Metabones unit for Canon EF lenses on the EF-M bodies as soon as they make one! Those would have full AF and electronic connection and I could still use my manual lenses with the various EF adapters I have. I recommend the Metabones and/or Lens Turbo focal reducers.

Tamron SP 500mm on Canon 5D Mk III ISO 400 1/6 second @f/8

Tamron SP 500mm with SP 1.4x TC on Canon 5D Mk III ISO 400 0.4 seconds @ f/8 (effective 700mm f/11)

Tamron SP 500mm on Canon M5 ISO 400 1/15 second @ f/8 (effective 800mm f/8)

Tamron SP 500mm on Canon M5 with SP 1.4x TC ISO 400 1/6 second @ f/8 (effective 1120mm f/11)

Tamron SP 500mm with 0.72x FR on Canon M5 ISO 400 1/25 second @ f/8 (effective 576mm f/5.6)




I am not sure if anyone has started a support group for people with too many 50mm lenses… I stand up and say, “Hello my name is Rod and I have more than dozen fifty millimeter lenses” The group says in unison, “Hi Rod!” And so the therapy begins. I just shoot pictures for therapy and what better way than with a whole tanker load of lenses!

Today I want to chat up the fabulous fifties and as you can already ascertain, I’m not talking about Elvis, malt shops, drive in dining, or rockin’ around the clock. I am talking about the 50mm lenses and their impact on photography. For 35mm and full frame digital this is a standard or ‘normal’ lens. Standard is probably the better name as one can ask, what really is “normal?” The theory has always been that 50mm on FF closely approximates the angle of view for human vision excluding peripheral vision. Standard seems to encompass the focal range of 45mm-58mm, the best of which depends on who you ask. The 50mm lens on full frame offers an unexaggerated perspective and sometimes that’s just perfect.

In our modern expanded photo universe of adapters and crop sensors like APS/c and MFT the 50mm focal length pushes its way into the portrait length as well. 50mm lenses are as versatile as ever before. The best thing about the fabulous fifty is the wide availability and thus relatively inexpensive pricing. The modern camera no longer comes with a 50mm as the “kit lens” like the old 35mm film days when a 1.8/50, 1.7/50 or 2.0/50 were standard fare for a new camera buyer. These days cameras typically come with a standard zoom kit lens. For FF that might be something like Canon’s 24-105 F/4 L USM IS on a 5d series body or on a crop sensor body like a rebel, maybe a 18-55mm kit zoom.

These kit zooms are surprisingly good optically even on cheaper cameras, but they lack one very important feature; a wide aperture. Typically an 18-55mm kit lens on a camera like a Canon Rebel will have a variable F stop from f/4 at the wide end to F/5.6 at the tele end. Soft backgrounds with good subject isolation can be difficult and sometimes impossible with 55mm F/5.6. A 50mm lens with the modest F/2 will deliver a world of difference in isolating your subject.

So why exactly do I have this ridiculous collection of a dozen or more lenses in the 50mm range? Well in a word, “Character.” No not personal character, lens character. Modern lenses tend to be very similar as computer lens design and modern manufacturing efficiency has led us to a world of near perfect lenses. Sometimes however, perfect is boring. Sometimes a little character goes a long way. Today I am going to compare this group of lenses and what makes them desirable and fun, at least for me. I will be using very subjective measures for the most part but I also have some basic objective analysis as well.

The lenses are as follows with links to past posts about them:

  • Bell and Howell 50/1.2 (16mm projector lens, covers APS/c mirrorless) 
  • Canon EF 50/1.4 USM (full frame DSLR or mirrorless)
  • Canon LTM 50/1.8 (full frame rangefinder/mirrorless)
  • Canon LTM 50/1.2 (full frame rangefinder/mirrorless)
  • Canon FD 50/3.5 Macro (full frame DSLR or mirrorless)
  • Cosmicar TV 50/1.4 (C-mount televsion lens covers APS/c mirrorless)
  • Jupiter LTM 50/2 (full frame rangefinder/mirrorless)
  • Kamlan 50/1.1 (APS/c mirrorless)
  • Pentax SMC 50/1.4 (full frame K mount SLR)
  • Zeiss Planar 50/1.4 (Y/C mount) (full frame DSLR or mirrorless)
  • Zeiss Jena 50/2.0 Pancolar (zebra pancake, Exakta mount) (full frame DSLR or mirrorless)
  • Zeiss Jena 50/2.8 Tessar (Exackta mount) (full frame DSLR or mirrorless)
  • Zeiss Jena 58/2 Biotar T (Exakta mount) (full frame DSLR or mirrorless)
  • Zenit Helios 44-2 58/2 (M42 mount) (full frame DSLR or mirrorless)

The street price for these lenses runs from well under $100 to maybe $700 for a really pristine example of the Canon LTM 50/1.2.

The Bell and Howell projector lens and Cosmicar TV lens are those fun projects for mirrorless that make owning a mirrorless camera so much fun. The lenses have crazy bokeh and get real soft at the edges and that can make for fun artistic representations. Both of these must be used on mirrorless due to a short flange to sensor distance and they will not cover full frame so APS/c or MFT only. These kinds of lenses can be found for less than $50 or maybe up towards a hundred if they are already custom converted for you camera. I have a C-mount adapter for my EOS M5 so I can mount many C-mount video lenses easily. When mounting an odd lens, be very careful to make sure that the rear of the lens will not come in contact with your camera’s electronic contacts or the sensor. When in doubt, abort the mission 😉

The Canon EF 50/1.4 USM is a solid performer with a fast aperture and quiet and quick auto focus. This lens is still available new from Canon in the $300 range but used examples are around in the $150-$250 range. The lens is notorious although unfairly so, for AF failure and Canon repair will run $150ish. The lens is not as sharp as the cheaper EF 50/1.8. It is better built, and has the USM instant manual focus motor. it is a half stop faster as well at F/1.4. For Nikon users the AF Nikkor 50/1.4 lenses are a bit better optically than this Canon EF 50/1.4. This lens is a full frame DSLR lens and as such it can work on focal reducers with APS/c and MFT mirrorless cameras. With a 0.72x unit you end up with a 36mm f/1.0.

The Canon LTM 50/1.8 was a lens made for the Canon rangefinder cameras. The design was one of Canon’s best achievements historically. The version I have is one of the later models but I have owned several over the years from early 1950s up to this early 60s model. The early models had a shiny polished look and were very heavily built, Canon went to a lighter build in the sixties, not to cheapen the lens but to literally lighten it, those early lenses were HEAVY! The historical significance of the lens is that it can arguably be said, it changed Canon forever! This lens marked Canon’s emergence as an innovator rather than a copycat. Canon’s history of making Leica clones would change in the 1950s as Canon began to experiment with unique designs for rangefinder cameras. The 50/1.8 lens designed by Itō Hiroshi shocked the world in 1951 and most importantly, Leica. The lens is demonstrably sharper and more contrasty than the Leica Summar and Summitar F/2 lenses that were available in the early fifties. Oh and an extra 1/2 stop of speed to go with those sharper images. Without Mr. Hiroshi’s magnificent design we might not have gotten the Summicron 50/2 which Leica brought to market in 1953. The game was now afoot. These amazing lenses are available in the $150-$250 range as good as a similar vintage Leica Summicron for a fraction of the cost.

The Canon LTM 50/1.2 is not as sharp as the legendary 1.8 unless you stop it down to F/2. But why carry a 400g (15oz) lens if you are not going to take advantage of that HUGE aperture? I owned one of these, sold it, missed it, and bought another one. What I missed was the bokeh. It can be a little busy, but in the right types of shots the bokeh seals the deal. The bokeh has a nice artsy look that sometimes makes the image pop. The lens also produces a coma glow on the edges at wide apertures and that can be really cool in an artsy sort of way. I really love this lens.

The Canon 50mm Macro lens is what it is, a lens that is design for higher magnification ratios and very close up photography. For what it does it does so well. Macro lenses are not really supposed to have any “character.” They are designed to render flat field sharp images with mag ratios of 1/4 to 2x life-size on the sensor. The Canon FD 50/3.5 is adequate, not outstanding, but pretty good, you can find minty examples for under $100 and that makes it a tremendous value. You could use this lens on a 0.72x focal reducer to get a 36mm F/2.5 macro not sure why you would though.

The Cosmicar TV lens was originally a C-mount lens for closed circuit TV cameras. My friend and fellow PhotoFair exhibitor Ashley Anthony modified it to permanently fit Canon EF-M so I bought it from him at the last show. It has a cool three blade aperture that makes wonky triangle football bokeh highlights. Very distracting but very cool. The lens is not real sharp but it is sharp enough and the strange backgrounds are worth paying $50 for something like this. The lens is a fun distraction from all this modern optical perfection we have to deal with 😉

The Jupiter LTM 50/2 is a little Russian lens for Zenit 35mm rangefinder cameras (Leica copies). It can be used on old Leica and Canon LTM bodies as well. This lens is not super sharp, but is decent enough. It has a very soft and non distracting bokeh. It’s really creamy and dreamy and that makes it worth the $50-$75 you spend on these. Mine has a very highly polished barrel that almost looks chromed. This lens also needs the photographer to be diligent about where you point it/ Keep the harsh light behind you and the lens does OK.

The Kamlan 50/1.1 is an APS/c and MFT lens available new for around $160-$180 in Sony E, Canon EF-M, MFT, etc. This is a value champion. Shoots like a 75mm-80mm on Nikon/Sony and Canon respectively. Feels like a 100mm on MFT. I wrote the lens up on this blog and it is soft wide open but still manageable. Corners are useless but for portrait sharp corners are unnecessary most of time. I still have this lens an I really like how small and light it is yet it remains reasonably well made. I love the creamy bokeh and the super shallow depth of field is challenging to focus, but awesome to utilize.

The Pentax SMC 50/1.4 is a solid lens. What I have always liked about Pentax brand lenses is the crazy small size that company manages. Why is every other major camera maker’s SLR 50/1.4 HUGE compared to Pentax? OK, Zuiko has a small 50mm as well but Pentax has always had these amazing compact lenses and they perform really well. They did have a bad habit of using crappy 6 blade aperture systems. Stop this lens down and out of focus highlights are ugly hexagonal blotches. Yuck! But this is a 1.4 lens and if I want to shoot at F/2 I can save a tone of cash and a bit of weight and buy an SMC 50/2. Wide open the bokeh is moderately smooth and the lens is pretty sharp too.


The Zeiss Planar 50/1.4 is one of the first lenses I reviewed on this blog way back in February, 2014. What can you really say about Carl Zeiss that hasn’t been said already. legendary performance and with these Contax/Yashica mount lenses from the late 70s- early 90s you get gold standard performance at an almost affordable price 😉 This lens is very sharp right out to the edges, has exceptional color and contrast, built very well with smooth controls, and is just an all around stud. You will find rough ones selling for around $200-$250 super clean ones in the low $300s. You might also seek out the F/1.7 version to save a few bucks. This lens was built for an SLR and as such it can be effectively used with a focal reducer to yield a 36mm F/1.0 ZEISS! Zeiss is still making these and several other classic lenses for modern camera mounts like Nikon, Sony, Canon. They have the chip inside to offer focus confirmation and will interface with the cameras electronics. They won’t AF though. The modern versions can be quite spendy so I like grabbing to older Contax/Yashica mount versions and pocketing some gold.

The Zeiss Pancolar 50/2.0 is a fabulous lens. I bought a Zeiss Biotar from Pacific Rim Camera, who will be at the Portland PhotoFair Show in September BTW, and I saw he had a Pancolar Zebra as well so he made me a sweet deal on the pair. The Pancolar is one of the biggest surprises I ever got with a cheap old Zeiss lens. This one made to fit Exakta cameras and those are SLRs so I can use it on my EOS 5D Mk III, my M5 where it shoots like an 80mm or on my M5 with a focal reducer whereby it becomes a 36mm F/1.4. This lens has a bokeh similar to the Canon LTM 50mm F/1.2. It can be a little busy, but it also can make the image. It only has a 6 blade diaphragm so stopped down you can get some trapezoid bokeh highlights that kind of suck. Wide open it is very sharp even towards the corners. The lens is a bit of a pancake design so when used on a DSLR it is tiny. These were made in the Jena factory which was in East Germany after WWII. The “zebra” desribes the very cool striped pattern between black and polish metal. I always liked the zebra lenses! This lens is contrasty with great color and razor-sharp. I simply wasn’t expecting that. yes, I know it’s a Zeiss but it’s post war East Germany and it’s 65 years old! These sell in the $50-$75 range GET ONE!

The Zeiss Tessar 50/2.8 is a lens I picked up at a PhotoFair show. These are cheap routinely selling in the $50 range. The lens is made to fit Exakta and as such it works on DSLRs with an adapter and can work on my APS/c M5 shooting like an 80mm and with the focal reducer a 36mm F/2. This is a very small and compact lens that looks more like a rangefinder lens than a SLR lens. Tends to flare a bit and the contrast is sub-optimal. But it is plenty sharp. Keep the light right and the lens pointed away from harsh light and it performs very well indeed.

The Biotar 58/2.0 I mentioned above is one of those classic lenses from yesteryear. These are known as sharp lenses that have a very Petzval style to the bokeh that swirls all around the subject at times. Who doesn’t like swirly curly bokeh, right? This lens didn’t perform optically as well as the Pancolar but it is better than Tessar. The bokeh is the real charm with this lens. This is also a lens for Exakta but you can find it in M42 as well. The M42 version will fetch more money. Like the others you can use it on a DSLR or on a crop camera for a tele that on my M5 shoots like a 92mm or with the focal reducer for a 67mm F/1.4.

The Zenit Helios 58/2.0 is literally a Russian copy of the Biotar made for Zenit SLRs in M42 mount. I have and older version the 44-2 which is a bit soft and has terrible contrast, flat color, and flares like sinking ship. You really have to be careful shooting this lens but it has soooo much charm. The same swirly curly bokeh that the Biotar exhibits without the Carl Zeiss optical quality. I actually love this lens, but make no mistake, you mount this lens you need to be focus on the artistic effects, don’t expect to make a grand landscape with it. Like the Biotar above it is usable on a DSLR and on crop cameras with or without a focal reducer. The chart below organizes data on the lenses. On the scale of 1-10 stuff 5 is average.

There you have it a bunch a cool fifties. I mentioned the use of a focal reducer and I am a big fan of these. Metabones started the craze back in 2012. The idea of a focal reducer goes way back to large Schmidt/Cassegrain telescopes. Back in the 70s you could get a focal reducer to shorten the focal length of your Celestron C8, C11 or C14. Metabones just made one for photographic lenses which require a bit higher grade of glass, design, and manufacturing. Since Metabones began marketing their Speedbooster focal reducers, others have joined the market. Zhongyi Optical makes the Lens Turbo which is very similar to the Metabones units. A number of other Chinese makers are also cranking them out.

They work by taking a full frame or 35mm film lens and focusing all the light onto the smaller APS/c or MFT sensor. When you shoot a full frame lens on a crop camera you are literally “cropping” the image. The lens is still gathering all that light to cover the full frame sensor but the crop sensor only uses between 25%-40%. The focal reducer uses optics to force most of that ‘wasted’ light onto the smaller sensor. This is why the F-Stop gets better. A 100mm lens F/2 has an aperture diameter of 50mm. Focal Length / Aperture = Focal Ratio 1:2 or F/2. When using a 0.72x focal reducer you still have a 50mm aperture but now have a 72mm lens, same formula 72/50=1.44 presto an F/1.4 lens. It does work although T values will not perfectly coincide since we are adding additional air to glass surfaces but that’s a another post. Now if Metabones will just make a Canon EF to EF-M so I can use my L lenses on the M5 with AF and electronic interface, I would be soooo happy. You hear me Metabones?

Be sure to come to the next PhotoFair or a camera show near you to find tables full of these old classic lenses. Modern cameras give these old dinosaurs new life and make cool images for you!




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