Evaluating the cheap focal reducer with "real world" images: part 2

I've been a bit tardy in this review. Poor weather and a busy job would to that I guess. This time though I've gotten a decent variety of images for testing 3 fast lenses with the cheap focal reducer.

The Bower (Samyang) 24mm F1.4 (17mm F1.0), Vivitar (Samyang) 85mm F1.4 (61mm F1.0) and a special case - Spiratone 135mm F1.8 (97mm F1.3).

So, here we have a wide 35mm Equivalent, short-tele/long portrait ~120mm equivalent, and telefocal ~200mm equivalent. When we say equivalent, we're simply comparing focal length of these lenses with what we would need on a 35mm "full frame" sensor to get the same angle of view.

For Part 1, click HERE.




These shots are from the Bower 24mm F1.4 (EF). As far as fast wide lenses go for full frame cameras, this is wide, fast and cheap. So you probably wont expect good optical quality, however I think anyone would be surprised to see how well it does. This is also a good choice for astro-photography.

ISO 200 1/2500 F2.8

ISO 200 1/100 F1.4

ISO 200 1/320 F2.0

ISO 200 1/800 F2.4

ISO 200 1/30 F1.4

ISO 200 1/25 F2.8

ISO 250 1/125 F2.0

Next up we have the Vivitar 85mm F1.4 (K). The lens has been modified slightly. Being a Pentax K mount, it will just work on any EF adapter really, but the lever gets in the way of the mirror on my 5D, so I clipped it off with a dremel. This lens is just fantastic on Full Frame. It's not too long to make it unwieldy, and the smooth bokeh is breathtaking. 

ISO 200 1/640 F2.8

ISO 400 1/10 F1.8

ISO 640 1/160 F1.4

ISO 200 1/500 F1.4

ISO 200 1/800 F1.4

Finally, here's pictures from the titan of the bunch, the Spiratone 135mm F1.8 (YS mount with F adapter). This lens is impressive. It's not much longer than the 85mm, but it's 82mm filter and massive elements immediately tell your brain to put some strength in your arm when picking this up. Then you're surprised because you still should have used a bit more. It's heavy, solid, and will built. It's all metal, with straight, square lines. While prone to flare, it can deliver sharp detail, although some processing may be needed to bring out the best from this beast.

ISO 200 1/1600 F1.8

ISO 200 1/1600 F1.8

ISO 200 1/2500 F2.8

ISO 200 1/1250 F1.8

I'll have to get around to posting how my EP3 looks with these lenses.

Hope you enjoyed this as much as I do :) GAS (Gear Acquisition Syndrome) can be costly, but ofter buying used lenses can be quite cheap.

The focal reducer has gone beyond my expectations. The wider focal lengths are more usable, and the stop extra more light is fantastic. The center of the image shows a small boost in sharpness as well, and since the image is wider, it's also less prone to shake giving a couple advantages for sharper pictures. I haven't found any increase in flare, or odd bokeh.

The 24mm in particular is a favorite of mine, and has supplanted the Panasonic Leica 25mm F1.4 as the "standard" lens on my EP3. It's a combination of the 25mm Focal length, and F1.0 speed.



Happy Shooting!

Evaluating the cheap focal reducer with "real world" images: part 1

Focal reducers really set something off with the mirrorless world. Not only for Micro Fourthirds, which is my "main" system, but also APS-C systems from Fuji and Nex.

Under a Focal reducer, the APS-C systems are "full frame" equivalent, giving the same image with the same lens for a photographer. Micro Fourthirds still gives a bit of a crop with 1.44x, but that's still pretty usable.

I figured I'll try some older lenses and see what I can get with this focal reducer adapter. Not only can it be used with old Full frame lenses, but there's a couple APS-C lenses out there as well, which would be very well utilized to deliver a wide image. I don't have many APS-C coverage lenses, because most would not have an aperture ring. I do have a samyang 8mm fisheye for APS-C. Looking forward to their 10mm lens.

The following Shots are from a Vivitar 17mm F3.5 (Nikon F). The lens is among the widest available from old film days, and delivers decent quality stopped down to F5.6. On the focal reducer, it's still not that fast, bearing F2.5, but it is wider than most MFT lenses, coming in at 12.2mm

ISO 2000 1/25s F5.6

ISO 320 1s F5.6

ISO 3200 1/25s F5.6

These shots are from the 8mm Samyang (Nikon F). Though it's a recent APS-C lens, it's completely manual, including the aperture ring. It should be noted that my copy never focused properly, and has been modified to achieve proper focus. Using this fisheye is very fun. While it is possible to "de-fish" the image to a rectilinear the fun and utility of a fisheye lies in the distorted projection. Ultra wide rectilinear lenses show heavy stretching towards the edge of an image.

ISO 400 1/20s F3.5

ISO 400 1/100 F5.6

ISO 400 1/80s F5.6

ISO 200 1/6s

ISO 200 1/2.5s F3.5

ISO 200 1/6s F5.6

These shots are from the Kiron 28mm F2 (Nikon F). Of all my old lenses, the quality here is probably the lowest. It's not a BAD lens. Few lenses are actually "BAD" This lens when stopped down is decent, but wide open is a little soft. Colors come out fairly well though. My pictures are probably looking repetitive here since my "testing" is really on my way home from my day job. I suck at street photography, so here's what we get. The third picture here looks extremely soft towards the bottom. All in all, I think the lens is quite usable. These pictures look nice and bright when in reality it was fairly dark outside. This is an effective 20mm F1.4, perhaps I should run a test of this vs the venerable 20mm F1.7.

ISO 400 1/80s F2

ISO 400 1/50s F2.8

ISO 500 1/20s

ISO 1250 1/40s F2

ISO 640 1/40s F2

These are the Canon 55mm F1.2 SSC (FD). This mount was converted to EF using the popular "EdMika" conversion kit. This is where we leave behind common thought and see what a $500 40mm F0.86 lens will look like. The focal reducer and 50 F1.2 combine to form a shockingly fast and capable lens. Shots here range from wide open (F1.2) to F2.

ISO 640 1/40s

ISO 200 1/40s F1.2

ISO 400 1/60s F1.2

ISO 200 1/60s

ISO 500 1/60s F1.2

ISO 400 1/60s F1.4

Up next I'll be trying lenses like the 85mm F1.4 and 24mm F1.4 Samyang lenses. I decided to break it up a little since the page loading gets heavy with too many pictures. 

It's interesting to note that even fast lenses on the focal reducer can be sharp and while it wont have as much contrast as stopping down a little, they can have enough contrast.

NB: to add ISO and shutter speed on these pictures comments. Blogger strips EXIF (why?!) 

A little test of 4 different 25mm F1.4 lenses on Micro Four Thirds

So, I'm not fond of formally testing lenses myself (though I do like to read em). Comparing a couple lenses may be fairly quick (quick and dirty may not check everything ☺), but putting four lenses into an easily readable report takes up some time. So I'm not doing this with too much depth. This is just to assert to myself the feel of these different solutions, that share the same 25mm f1.4 specification, and look at more obvious differences in their results.

This is a very different kind of roundup. There's only one lens here I'd expect people to come across "in the wild". The next most common is a C-mount so yes, lets get weird...

The lenses here (on my Olympus EP3) are:

1. Panasonic (Leica) DG Summilux 25mm F1.4 ASPH.
2. Pentax TV lens 25mm F1.4 (1" coverage)
3. Wollensak Cine Raptor 25mm F1.5
4. Nikon 35mm F2.0 AI Nippon Kogaku

First off, some of these names just simply sound exotic. It brings to mind images of awesomeness that simple named lenses can't match. Obviously, fancy names equal good image quality...
Sarcasm aside, I like these names. It really helps set these aside from just being a mundane amalgam of specifications.





About the lenses:

Summilux is what Leica calls their current batch of lenses with an F1.4 aperture. Leica itself is a luxury brand in cameras. Leica's been at this for a while - their compact landscape camera dates back to 1913. They've got history, and a name that carries weight, so it makes sense that Panasonic would want to ride that name. The lens is Panasonic made but designed or approved by Leica. This is a current production lens for the high grade MFT market.

The most pedestrian of names is the Pentax TV lens. Quality is a bit better than the cheap 25mm c-mounts lenses on ebay that go for $25-$50, but it's not that great. It is quite comfortable to use with it's smooth ring though. This lens still exists, but is now branded Ricoh. This is a current low cost CCTV lens. Stepless aperture is good for video. While Pentax is also steeped in optical history starting with spectacle lenses, a mass production and cheaper lens like this probably inherits little of their mojo.

Wollensak was making camera lenses as far back as 1902,and shutters from 1899. They pushed high speed photography and video with their fastax brand, developing on a Bell Labs spinning prism implementation taking frame rates up to 18,000fps in the 1960s. For their film cameras, they have a line of cine lenses (c-mount)that were good value at the time. The company went under in 1972, so the lens here is at least as old as that.
 
Nikon has been around since 1917, but at the time was known as Nippon Kōgaku Kōgyō Kabushikigaisha (say that ten times fast...). It stayed that way for a long time, but in 1988, someone thought that it was too much of a mouthful, so the company was renamed to Nikon Corporation. "Nikon" dates back to 1946 and was formed from the words "Nippon" and "Ikon". Ikon was a Zeiss brand. In 1959, Nikon started pushing their Nikkor F line of SLR cameras. The 35mm F2.0 in use is an optical design introduced by Nikon in 1962. In 1975 Nikon updated the lens to stop down to F22, and since my lens doesn't have that option, the age is between 1962 and 1975 - possibly closer to 1975 since Nikon initially used chrome noses instead of all black on their lenses.

The Panasonic Leica produces a beautiful rendering. It's sharp to the edge, and the bokeh is smooth. Focus is quick. Manual focus is horrible since the focus ring is electronically connected to the glass and not mechanical. however, this gives it a relatively compact size for this level of quality and speed. It should be noted - this lens would be auto corrected in the camera for certain traits (CA/distortion etc), so the JPGs used would favor this more than other lenses here.

Ye olde Nikon 35mm F2.0 on focal reducer. Slight difference in focal length. Quality is decent, but it's definitely not as sharp. I can't say it's purely the focal reducer or the lens, the fault is probably shared between the two.

That said, it's sharp enough to satisfy most and make a good picture. Bokeh is nice, maybe the nicest of the bunch. it's focused a few millimeters in front of the Panasonic, so blurring is a little different, but as you can see it's quite smooth.

Also of note - the entire image shows little or no light falloff. Even on a full frame camera, this lens was well known to deliver low vignetting.

I loved using this Wollensak lens. Before MFT had a lot of lenses available, people were adapting any fast prime they could find to get a decent F-Stop. Classic manual focus 50mm lenses were common, and cheap, but they were also an equivalent 100mm on this format. The field of view more specific in usage compared to a "normal". C-mount lenses like these 25mm lenses were perfect fits for the system - small, light, and some actually delivered decent quality.

The Wollensak here shows a very sharp center quality - surprisingly sharper than the 35mm F2.0 on focal reducer. while it's not quite F1.4, the F1.5 is close - however it was never meant to cover this large a sensor. Resolution and brightness both fall off at the edges. Heavy vignetting here. It's a decent lens for individual shots giving an artistic effect, but not a good choice for a sharp clear picture.

Looking at the F-keys at the bottom you can somewhat make out the most interesting characteristic of this lens, and it's the way bokeh is rendered. Blurring is somewhat radial about the center of the lens, and produces a unique effect with background lights.

Distortion is pretty bad, but you know what you're getting into with this lens. Again - One of my favorites, but you have to work within the character of the lens.

This Pentax is the cheapest of lenses here - not just in cost really (this was purchased new) but in design, feel, and optical quality. A Modern c-mount. The very tips of the corners have vignetted to almost nothing. Like the Wollensak above, there's distortion, vignetting and it gets worse at the edges but unlike the Wollensak, the center isn't nearly so spectacular, and of course we see a characteristic glow on object edges with this lens used wide open. Cheap lenses like this often exhibit a curving focal plane - i.e. as you move from the center of the lens to the edge, an object may have to move closer or further away from the plane of the lens and sensor to stay in focus.

Of course, the question here is "is this usable?" - again like the Wollensak, there's a lot of "character" i.e. imperfections you need to work with. It can give you a decent picture if you try. The redeeming aspect of it is it's weight, and ease of focusing. the focus moves smoothly and easily between the index finger and thumb.

So that's 4 lenses - 3 different types that are 25mm F1.4. There's no MTF curves or going into technical details here and I'm only looking at them wide open - so this article's usefulness will be rather specific, but I think it's interesting to see them here. As evidenced, everything is a tradeoff. Size, cost, build quality, ease of focus, sharpness, vignetting, chromatic aberrations - even the high end Leica here loses to all 3 in ease of manual focus, and the 35mm easily has it beat for vignetting. Every lens here has something it's better than the others at - even the optically worst lens of the bunch has redeeming qualities. Photographic gear is an exercise in compromise. 

I have a crapload (technical term for a lot) of lenses with overlap. But it doesn't mean I don't have a reason to use them. Sometimes I run with the Wollensak just for fun. Since I'm heavy into manual lenses, it's good to keep practicing focus. The results are different, and can be quite fun when done right - say, taking a photo of someone in front of a Christmas tree and seeing the swirly bokeh transform the background of image into a more atypical picture.


Everyone with an interchangeable lens camera should try a manual focus lens sometime. You may like it - and if you do, you suddenly open up decades of easily adaptable glass, often with wider apertures that you'd normally get as a result of cost - and with a focal reducer, that F-Stop can become even better, while supplying a wider angle of view.

Wollensak 25mm F1.5 - "Some dude on a bike..."
Sharp center makes the bike "pop". Less sharp edges don't matter here, and the distortion is somewhat masked by motion blur.

Focal Reducers with DSLR lenses and light gain math...

A focal reducer is a set of lenses that essentially concentrate the rays of light coming from the back of a lens, into a smaller area.

Metabones commercialize it for adapting SLR lenses to mirrorless, but didn't invent the focal reducer. Astronomers have been using them for quite some time, and Enterprising DIY users were toying with them and SLR lenses/cameras as well.


A lens is circular, and will produce a circular image (usually - funny baffles and built in hoods not withstanding) - hence it is "creatively" called the "image circle". The focal reducer will make the size of this circle smaller (while keeping minimum and maximum focus distance constant).

In making the circle smaller, it packs rays of light more tightly together. The effect of this is it will make the image brighter, and can actually increase the MTF (think sharpness of details) of the lens on that camera.

The other effect is since the image circle is smaller, parts of the image circle (if it was large enough) would come into view, making the lens appear wider.

There's 2 ways to think about it. You can think of it as a wider, faster lens. Or you can think of it as making your camera sensor larger. The camera will see the lens and focal reducer as ONE UNIT. Both of them together is just a lens to the camera. If we look at a focal reducer on the camera from the lens' perspective, light rays just see a bigger sensor. This is also evident if you just look down at the camera. Here's a picture to explain that:

The lines are to show dimension. you can try counting pixels if you really want. you'll find x/x' and y/y' both roughly equal 0.72

For example - my 55mm F1.2
I'm using a focal reducer on my Micro Four Thirds camera, of 0.72x

The crop factor is 2 (1/4 the area)
The equivalent angle of view compared to full frame is 110mm.
The equivalent depth of field compared to full frame is 110mm @ F2.4
Light gathering stays F1.2 - but smaller sensors  are getting less light, so raising ISO (sensitivity) generally introduces noise much faster.

You'll see tons of arguments one way or the other. These are just numbers. They're neither good nor bad. Crop sensors (sensors smaller than fullframe) exist for a reason.

Anyway, so my 55mm F1.2, effective looks like a 110mm F2.4 on a MFT camera (but light gathering stays F1.2).
Putting on a focal reducer (0.72x) my 55mm F1.2, becomes a (55 x 0.72)mm F(1.2 x 0.72) lens - i.e. 39.6mm F0.864!

With and without the focal reducer - think of it as changing the lens to something wider and faster! This was a cheap generic chinese adapter selling for $100 on ebay.

So, what's the effective lens parameters now? 39.6mm F0.864 on a crop factor of 2 becomes 79.2mm F1.728. A pretty decent portrait lens. Again, light gathering stays with the lens - F0.864, so this makes smaller sensor cameras highly capable in low light.

The other way to think about a focal reducer is it makes the sensor effectively larger from the perspective of the lens. Lets do the math.
My crop factor 2 becomes a crop of 2 x 0.72 or 1.44. That's even bigger than APS-C sensors.
Assuming the crop of 1.44, the calculations are applied to each lens used - (55 x 1.44)mm F(1.2 x 1.44) = 79.2mm F1.728.

Light concentration gain? Still have to consider sensor original size or the focal reducer strength here F(1.2 x 0.72) or use the effective aperture and divide by original crop factor = F1.728/2 = F0.864.

I've expressed light gain in terms of aperture. Here's the math to understand what that means in terms of actual light.
change in light = (old F-Stop/new F-Stop)² - I'll explain later

So the F0.864 light gathering compared to F1.2 is (F1.2/F0.864)² = 1.93 times brighter. In other words, we're a stop brighter - effective ISO is doubled.

An alternate way to calculate would be direct from the focal reducer parameter of 0.72x. (1/0.72)² = 1.93.

Finally, here's the math to understand "change in light = (old F-Stop/new F-Stop)²"

lets say we're using a lens of focal length 100
the aperture is a particular size say, 50mm, so our F-stop is F2.

Light coming in is proportional to the area of the aperture. 
Area = πr²
since we're working with diameter and diameter is 2x radius:

Area = (1/4)πd²
light concentration is proportional to aperture area, therefore:
Concentration = k(1/4)πd²
Since k is arbitrary, let's wrap up pi and 1/4 into a general constant:
Concentration = jd²
F-Stop = Focal length[L]/aperture[d]
so...
d=L/F
Now lets relate light concentration with F-Stop

Concentration = j(L/F)²
Since L is a constant for a given prime, let's wrap that into the other constant.
Light concentration = k/(F²)
i.e the amount of light is inversely proportional to the square of the F-Stop.
Comparing new and old F-stops:
to show concentration gain = (old F-Stop/new F-Stop)²

Light concentration new = k/(F'²)
Light concentration old = k/(F²) 
The amount of light I'm getting compared to before is
Light concentration new / Light concentration old
i.e. 
[k/(F'²)] / [k/(F²)] = F²/F'²
Where F is old F-Stop and F' is new F-Stop.

Basically, one f-stop is twice as bright as another, if it's 0.707 the value of the other (1/√2).

FUN RIGHT!!!!!

The 55mm F1.2 on my EP3 using a cheap chinese focal reducer 

 Generally F1.0 and faster lenses cost an arm and a leg for the first installment. This adapter gives me an effective ultrafast lens adding only $100 (adapter cost). The Canon SSC FD 1.2 is about $350 (usually less) on ebay. A brass mount replacement to EF is about $130, so about $580 for a ~40mm F0.85. Very useful for getting less depth of field at a comfortable angle of view, and of course doubling light gain. Cheaper to go Nikon here normally.

Another use is taking good APS-C lenses, and making them incredibly wide on Micro Four Thirds - e.g. the 11-16mm Tokina, will be reduced to ~8-11.5mm, giving a 16mm equivalent wide end. Sigma's 8-16mm would become an astonishing 11.5mm. Of course this would only work well if the lenses are capable of manually being focused. Aperture works with manual lenses since they're designed with the aperture ring.

I'll be playing around with this in the future, but so far, I'm surprised with the optical quality. I don't think details are diminished at all, and I've not yet seen bad flare. Sharpness of this combo is good, but doesn't compare with the 25mm F1.4 Leica that was designed for MFT from the start. It does however make it look like a dark lens by comparison, which is an amazing accomplishment.