Seeking advice: New lens: Nikon 105 f2 DC or Fuji 90 f2

SpacemanUA wrote:

MisterHairy wrote:

135/2 > 90/2. The 135 has an aperture which is 2.25 x as large by area.

Lets more light in.

Is faster.

You're messing up DoF with light transmission. And the "aperture area" is a nonsense.

f/2 means that a lens transmits 1/2 of incoming light through itself, and it doesn't matter, if its made for m4/3 or FF or MF or how big is that lens is. If its f/2, its always f/2. F-number always and only means the amount of light transmitted. 90/2 and 135/2 lenses transmit 1/2 of incoming light through themselves hence they're have same "speed". As for lens diameter (not aperture diameter or area) - F-number depends on it too, so if you're counting it twice, you're obviously wrong.

As for DoF - 135/2 will have harrower DoF than 90/2 obviously.

You are mixing f-stop up with t-stop and my aperture area comment is 100% correct.

The maximum f-stop of a lens (in these two cases, f/2) is, quite literally, the ratio between the focal length and the maximum aperture of the lens. Always has been. So a 135mm lens with a maximum aperture of f/2 has a maximum aperture diameter of 135/2 = 67.5mm.

A 90mm FL lens with an f-stop of f/2 has an aperture diameter of 90/2 = 45mm. The area of the aperture is PI.r^2 = 1590mm^2.

a 135mm FL lens with an f-stop of f/2 has an aperture diameter of 135/2 = 67.5mm. The area of the aperture is Pi.r^2 = 3578mm^2.

3578/1590 = 2.25.

The “speed” of a lens has nothing at all to do with the sensor/film that is behind it; it is solely a property of the lens.

it may serve you well to do a bit of reading into the subject lest you continue to get these fundamentals wrong.

sdbrock wrote:

Is this because the f-stop is a ratio?

Yes. It is the ratio of focal length / aperture diameter. It is a physical characteristic of the lens and is independent of camera/sensor/film.

Good to know.

Cheers

MisterHairy wrote:

sdbrock wrote:

Is this because the f-stop is a ratio?

Yes. It is the ratio of focal length / aperture diameter. It is a physical characteristic of the lens and is independent of camera/sensor/film.

The only thing that matters is how much light hits the sensor. This is why the Nikon 105 F2 is still an F2 on an aps c body.

If you were correct, everyone would be buying FF lenses exclusively for their aps c gear since your bad math magically turns the lens into a much faster lens than it is on FF.

Steezus wrote:

MisterHairy wrote:

sdbrock wrote:

Is this because the f-stop is a ratio?

Yes. It is the ratio of focal length / aperture diameter. It is a physical characteristic of the lens and is independent of camera/sensor/film.

The only thing that matters is how much light hits the sensor. This is why the Nikon 105 F2 is still an F2 on an aps c body.

If you were correct, everyone would be buying FF lenses exclusively for their aps c gear since your bad math magically turns the lens into a much faster lens than it is on FF.

What bad math, pray tell? My comments about aperture size are correct and if you read what I have written, I have said that a lens' "speed" is a characteristic of the lens and is not dependent upon the camera, sensor or film. An f/2 lens is even an f/2 lens if it not connected to a camera.

A 135/2 lens does have a larger maximum aperture than a 90/2 lens; it is more than twice as large in terms of area.

(By the way, just to confuse/enrage you even more, if you were to take the same 135mm f/2 lens and put it on two cameras, one with a "35mm" sized sensor and one with an APS-C sized sensor, more than twice as much light will land on the 35mm sensor per unit of time because it has more than twice the surface area of the APS-C. The light which falls outside of the APS-C sensor's area is lost as it is not collected by the sensor. The light per unit area per unit time is the same for both sensors, but you said "how much light hits the sensor" and that is not the same.)

MisterHairy wrote:

What bad math, pray tell? My comments about aperture size are correct and if you read what I have written, I have said that a lens' "speed" is a characteristic of the lens and is not dependent upon the camera, sensor or film. An f/2 lens is even an f/2 lens if it not connected to a camera.

And what's the point of your speech then? Just to get us know that 135/2 has bigger entrance pupil diameter? Breaking news!

A 135/2 lens does have a larger maximum aperture than a 90/2 lens; it is more than twice as large in terms of area.

Who cares? A lens is supposed to cover APS-C sensor in our case, so even if it would've been 500m in diameter, in won't change anything. It will transmit same 1/2 portion of light through it and will have same "speed" as 90/2, cause 90/2 is just big enough for APS-C sensor. Who the hell measure this "aperture area" if aperture is a relative value in camera lenses.

SpacemanUA wrote:

MisterHairy wrote:

What bad math, pray tell? My comments about aperture size are correct and if you read what I have written, I have said that a lens' "speed" is a characteristic of the lens and is not dependent upon the camera, sensor or film. An f/2 lens is even an f/2 lens if it not connected to a camera.

And what's the point of your speech then? Just to get us know that 135/2 has bigger entrance pupil diameter? Breaking news!

A 135/2 lens does have a larger maximum aperture than a 90/2 lens; it is more than twice as large in terms of area.

Who cares? A lens is supposed to cover APS-C sensor in our case, so even if it would've been 500m in diameter, in won't change anything. It will transmit same 1/2 portion of light through it and will have same "speed" as 90/2, cause 90/2 is just big enough for APS-C sensor. Who the hell measure this "aperture area" if aperture is a relative value in camera lenses.

You may benefit from some background reading on the topic. Don't feel bad; lots of people don't know what all of those funny numbers on lenses mean, but if you are going to spread information on the internet then it might be helpful if it weren't misinformation. You are doing others a disservice with your bunkum.

You are too funny with your ironic comments about not understanding.

Trust me, you are the one misunderstanding what you are reading.

Steezus wrote:

You are too funny with your ironic comments about not understanding.

Trust me, you are the one misunderstanding what you are reading.

Oh dear. Maybe you should stop now.

Just in case you do feel like bucking the trend and educating yourself, here's a nice simple reference for you:

https://en.wikipedia.org/wiki/Aperture

Please pay particular attention to the section a bit more than half way down the page titled "Aperture Area" where it states:

(quoted from Wikipedia)

The amount of light captured by a lens is proportional to the area of the aperture, equal to:

(end of quoted section from Wikipedia)

Simples.

Now, of course you might say that Wikipedia is not 100% reliable on all topics, and of course, it isn't, but it is right here. Aperture area governs how much light can pass through a lens. It's obvious; a bigger hole lets more light pass through.

It is such a basic concept that you are overlooking. If only lenses were smart enough to focus the image circle onto whatever format sensor it is attached to, but it is not. Again, the only thing that matters is how much light hits the sensor, not how much goes through the lens. Your arrogance is astonishing for someone that has totally glossed over such a simple concept.

A strange choice really. Both are too long for portrait lenses when used in DX mode although that is clearly my personal opinion. The Fuji 58mm F1.2 vs the Nikon 58mm F1.4 would be more interesting on DX. Then I just realised you mentioned the metabones.... OK  I see where your going on this

The Nikon 105 dc is regarded as the best portrait lens of all time by many. The reason is simple.... its bloody superb lol.  To offset that... it is also regarded as a one trick pony, in that portraits is all it is good for. I disagree with that myself as it is a good performing lens in general. The 105 DC just lives and breathes character with superb fall off. Given the Fuji X trans itself does a similar thing for sensors... well that's a combo I would love to see myself.

If you are certain that manual focus is just not a problem I would absolutely go for it !

The one and only thing that i did not like with the 105 DC is its close focus performance was poor. However... used in conjunction with a metabones... that should act as a sort of extension tube which will certainly solve that problem. Love the idea myself lol