@Alex About your quote of the review: "...real aperture of the lens is much closer to f/1.8 than to f/1.4 or/and wrong conctruction of the diaphragm...", if this is true, then is is probably more like f/2.0 or f/2.2 on a m43 camera. This is because the effect of increasing aperture is reduced with small photosites on sensors. The bigger the pixel, the more effect increasing aperture is going to have.

So even if it was f/1.4 on a FF camera, it would probably be closer to f/1.6 or f/1.7 on a m43. Ill try to find the article about it for reference.

@Vitaliy_Kiselev I was referring to the amount of light that gets into the smaller photosites. Not the amount of light that the lens passes to the sensor. I cannot find the source link for the life of me. It showed data graphs which explained it well.

BTW, this should be called off-topic but I'm stuck here.. Anybody wanting to know which China eBay seller not to buy Fotga Nikon-M4/3 adapter from, I'll be happy to provide info by PM.

I Wrote:

("10 *rubber days" started on 28th January - but that's a whole 'nother story).

Seller claims to have sent item yet again and is wringing hands & asking pretty please to wait a third time..

@joethepro This Hoary, 3-year old story of yours may interest some people if you'd like to start your own PV Flame - but it doesn't interest us Samyang 24 users, sorry.

@joethepro No focus play.

In case anybody has been looking the gift horse 25mm in the mouth so much they haven't noticed: this is your normal lens, the one you can use as your only lens, all day and all through a feature film! - and the sheer discipline: framing right, walking up close to get the right shot - can force you into making the right decisions.

Probably somewhere, some poor but smart kid who knows what matters has just managed to come up with the $300 for the Samyang 24 and another $400 for a hacked GH2 and and is about to give rich dumb folks a run for their money.

@joethepro - As Vitaliy noted, the "f-stop" is the f-stop of the lens. While there can be a slight bit of variance depending on the manufacturer, it should be pretty darned close. It is based on the amount of light that hits a certain amount of surface area of sensor. However, mft cameras have a sensor that is approximately 1/4 the size of digital full frame cameras. This means that a mft sensor receives 2 stops less total light on the sensor than a full frame sensor (each "stop" representing a halving or doubling of light).

When evaluating comparative EXPOSURE values between mft and full frame lenses, the mft lens f-stop is doubled (2 stops). Thus, a f/1.4 mft lens provides the same amount of light to a mft sensor as a full frame f/2.8 lens does to a full frame sensor, ceteris parabis (exposure time and iso being equal). That is why many full frame fans (correctly) note that the effective amount of light that a "f/1.4" mft lens isn't "really" equivalent to a f/1.4 FF lens.

IMO, Tony Northrup has done as good a job as anyone, over three videos on YouTube, explaining this. It is well worth a watch to refresh the concept for anyone who is interested.

However, this is a function of sensor size, not lens aperture. What I don't understand is why lens manufacturers like Samyang don't take their FF lens and change the rear lens element on the FF lens so that it focuses the light "circle" so that it covers only the mft sensor, much like Speedboosters do. This way, the lens would provide nearly equivalent light "per pixel" on mft as it would on FF and close to the same sharpness at a much lower price than we are seeing with mft lenses. Can you imagine a mft f/0.7 lens for <$750?!?

On the other hand, this points out that mft lens manufacturers are making a LOT of money on their lenses. While the Panasonic 12-35mm "f/2.8" mft lens is much cheaper than the FF 24-70mm focal length equivalents, it is really the equivalent to a f/5.6 FF lens as far as light on the sensor is concerned. A FF 24-70mm f/5.6 lens from Nikon or Canon would probably be much cheaper than what Panasonic is currently charging. In that respect, the 12-35mm isn't as price attractive anymore. Still attractive for the focal length, if not for the total light on the sensor. Again, it is an effect of the sensor size.

On the other hand, the sensitivity of modern mft sensors (GH4) are at least equivalent to the original FF Canon 5D and approach the sensitivity of the 5DMkII. Because of this, such comparisons are only equivalent with modern sensors. So those people shooting with 5DMkII's can't really say all that much. OR anyone shooting with a Canon APS-C camera.

Hope this adds to the conversation... :)

@joethepro - If you are using a straight mft adapter on the Nikon AIS f1.4 (I have one, it is a great lens for the $75 I paid for it!), because the sensor on the mft camera is 2 stops smaller than a FF sensor, the sensor receives the equivalent light from that lens of a FF f2.8 lens (f1.4 + 1 stop = f2 + 1 stop = f2.8). It FUNCTIONS like a FF f2.8 lens on FF camera, if the exposure time and iso are kept the same.

The "light circle" that the FF lens projects into the camera body is about 2 times the diameter (diagonal measurement) of the mft sensor. This means that ~3/4 of the light the FF f1.4 lens captures is NOT hitting the mft sensor.

You can see the difference in sensor size as square mm. A FF sensor is 36mm x 24mm. 36*24=864 square mm. A mft sensor is 17.3mm x 13mm. 17.3x13=224.9 square mm. 224.9/864=~26% or ~1/4 the size of a FF sensor.

http://upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Sensor_sizes_overlaid_inside_-updated.svg/587px-Sensor_sizes_overlaid_inside-_updated.svg.png http://upload.wikimedia.org/wikipedia/commons/thumb/9/95/SensorSizes.svg/428px-SensorSizes.svg.png

This is why the Metabones Speedbooster has become so popular with mft users of FF lenses. It takes the FF light circle and with the use of lenses in the adapter focuses more of it onto the sensor. A standard mft Speedbooster has a .72x increase in both focal length and aperture (.72x * 2x mft multiplier = 1.44x net multiplier). Thus, a FF f2 lens becomes a f2.88 lens on a mft camera rather than the expected f4 (f2 * 2 stop mft multiplier * .72 = f2.88). The Speedbooster also helps with focal length. A FF 50mm lens becomes a ~72mm lens (50mm * 2x focal length multiplier * .72 = 72mm).

Oh, a "FF multiplier" is 1.0x.

Alternatively, some people are using the Speedboosters for the Black Magic BMCC (.62x * 2x mft = 1.24x net, about APS-H) and BMPCC (.58x * 2x mft = 1.16x net, almost FF!) on their GH3 and GH4 cameras. However, there are some SIGNIFICANT caveats to doing so, including there being interference between these Speedboosters and the camera body shutter frame. There are a large number of videos on YouTube that discuss these issues. If only they could have been made even .5 mm shallower... ;-)

As I said, look at Tony Northrup's YouTube videos (below) on this subject. I think he does an excellent job explaining it. He even uses real world example pics so you can see the focal length/f-stop/DOF differences between FF and mft cameras.

On the other hand, because he presents it as a way that manufacturers are not "honestly" representing this information (they really aren't), he has caught a lot of flack (APS-C cameras also suffer from this, though to a lesser extent (1.5-1.6x vs. the mft 2.0x multiplier)). I just accept it for what it is.

Here are the two Tony Northrup videos I mentioned.

IMO, the mft camera system is phenomenal. I will NEVER move back to FF or APS-C (unless mft suddenly ends, which I don't believe it will). I don't do really dark photography/videography (many weddings, horror movies, etc.), so those lost two stops isn't as much of an issue as it would be for professional users. Even still, with videography, products like Neat denoise can compensate for at least two stops of difference. In good light, those two stops can be a BENEFIT!

Of course, those 2 stops also affect your DOF. They double it, compared to FF. IMO, that is an advantage when it comes to getting critical focus as you aren't dealing with those insanely shallow DOF, where the eye is in focus, but the tip of the nose isn't. That increased DOF also helps when trying to keep focus with a moving subject. On the other hand, that doubled DOF can make getting significant bokeh more difficult.

Back on topic, the Samyang/Rokinon/etc. lenses are quality lenses that appear to be more focused on video than photos. However, they appear to be high value lenses for what you get, if you fully understand all of the ramifications.

Since they are fully manual lenses that are available in both mft and FF, I would personally buy the FF version and then use it with a Speedbooster if I want the light/DOF/focal length back or use a straight adapter for "crop factor" usage. I really do not see any advantage to these lenses with mft mounts at the same prices as their FF equivalents. It would be a different story if they provided exposure/AF in a mft mount at the same price as the fully manual FF lens equivalent.

Hope this helps.

@Vitaliy - I understand. That is why I brought it back to the discussion of the lens at the end. I was only clarifying the point as it does affect specifically how these lenses work on mft cameras vs. FF. I'll be a good boy and stick strictly to the topic now. :)

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