# XF56 f1.2 released and specs

Started Jan 6, 2014 | Discussions
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Re: XF56 f1.2 released and specs

Yes, I follow your argument apart from one step which actually represents my original question:

>

For semiconductor sensors what matters is the total number of photons per photosite, pretty much regardless of the site area. Make two sensors: say an APS-S and FF ones both of say 16 megapixels. Expose them using the same scene for the same duration using 56/1.2 and 85/1.8 lenses respectively. Each photosite will receive the same NUMBER of photons (the number per unit area is 2.25 times larger in the first case, but the area itself is smaller by the same factor).

I agree with the area and scaling factor part, but my original question was whether it is true that the 56/1.2 will deliver the same number of photons per unit area on the APS sensor as the 85/1.8 lens on a FF sensor. I'd like to understand this part - Of course I understand that on an APS sensor the 56 lens results in an image with the same field of view as an 85 lens on a FF sensor.

Looking at the 85 mm lens and your statement that the 85/1.8 is equivalent to the 56/1.2:

Suppose we are looking at a uniformly lit scene.  Assume the 56/1.2 lens receives a total of N photons at its aperture.  These N photons are then spread over the APS sensor (ignore any losses at this point).  On the 85 lens, to get the same physical aperture area I agree that you need to stop down the lens to f1.8.  This will also capture N photons (uniformly lit scene, same number of photons per unit area).  However, in this case, the sensor area is now a factor of 2.25 larger, so those N photons result in fewer photons per unit area on the FF sensor (by a factor of 2.25).

To me, the only way to get the same number of photons per unit area on the FF sensor is to open up the 85 lens to f1.2........

The next stage - how those photons are transformed into an electrical signal is not something I know much about.  Maybe the FF sensor is so much more efficient than the APS one - but that is not an argument about the number of photons captured by different lenses any more.

Malcolm

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Re: XF56 f1.2 released and specs

There is allot of talk about equivalence to FF here and I must admit it's a little confusing. From what I gather 56mm ASPC is 85mm on FF in FOV. 1.2 is 1.8 in DOF. But 1.2 is 1.2 in light gathering. FF owners argue that because the FF sensor has bigger surface area so it's roughly about 1 stop better in ISO performance which negates the difference in light gathering from the lens. So you would shoot at 1.2 ISO 800 on ASPC and 1.8 ISO 1600 on FF and you get a similar quality image. I realise this probably very simplified.

What I'm curious about is how the lens behaves. An 85mm lens is a short telephoto and with that you get some compression which is why the background looks quite near to the subject and also gives a flattering look in portraits. Will a cropped 56mm lens behave the same way?

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Re: XF56 f1.2 released and specs

La Roque has a preview up:

http://www.laroquephoto.com/blog/2014/1/6/the-razors-edge-fujinon-xf-56mm-f12r

Probably won't satisfy critics, but I'm liking the results so far. Can't wait to shoot portraits with it.

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Re: XF56 f1.2 released and specs

This one is definitely on my list. One lens I  have not seen on the roadmap is a true telephoto, something like a 200F4. Hope they will eventually fill that void. Have had my XE2 two weeks, I love it.

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Re: XF56 f1.2 released and specs

malcolml1 wrote:

Yes, I follow your argument apart from one step which actually represents my original question:

>

For semiconductor sensors what matters is the total number of photons per photosite, pretty much regardless of the site area. Make two sensors: say an APS-S and FF ones both of say 16 megapixels. Expose them using the same scene for the same duration using 56/1.2 and 85/1.8 lenses respectively. Each photosite will receive the same NUMBER of photons (the number per unit area is 2.25 times larger in the first case, but the area itself is smaller by the same factor).

I agree with the area and scaling factor part, but my original question was whether it is true that the 56/1.2 will deliver the same number of photons per unit area on the APS sensor as the 85/1.8 lens on a FF sensor.

No, it will receive 2.25 times more photons PER UNIT AREA.

To me, the only way to get the same number of photons per unit area on the FF sensor is to open up the 85 lens to f1.2........

What is so damn important about number _per_unit_area_? I really don't get it. For all image quality purposes it's an irrelevant parameter.

The next stage - how those photons are transformed into an electrical signal is not something I know much about. Maybe the FF sensor is so much more efficient than the APS one

No, it isn't any more efficient. It doesn't need to be. It's just 1.5 times bigger, which is enough to achieve over one stop signal to noise gain (or to perform on equal foot at 2.25 times lower illumination level).

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Re: XF56 f1.2 released and specs
1

Asylum Photo wrote:

La Roque has a preview up:

http://www.laroquephoto.com/blog/2014/1/6/the-razors-edge-fujinon-xf-56mm-f12r

Probably won't satisfy critics, but I'm liking the results so far. Can't wait to shoot portraits with it.

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Not bad, but highlights outlines are pretty rough. Impossible to evaluate sharpness at this image size.

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Re: XF56 f1.2 released and specs

I'm sure it will be a great lens but heck...£1000 is pretty eye watering.

I took this pic with a 30 odd year old manual Rokkor 50mm f1.4 that i recently picked up for £50, it will do me nicely thank you

I also have a 58mm f1.4 Rokkor and a bunch of otherRokkors with adaptors, all for less than the cost of the XF35mm. It's a funny old world !

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Re: XF56 f1.2 released and specs

Krich13 wrote:

What is so damn important about number _per_unit_area_? I really don't get it. For all image quality purposes it's an irrelevant parameter.

Because that is an essential part of exposure. You can use a faster shutter speed.

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Re: XF56 f1.2 released and specs

Krich13 wrote:

Asylum Photo wrote:

La Roque has a preview up:

http://www.laroquephoto.com/blog/2014/1/6/the-razors-edge-fujinon-xf-56mm-f12r

Probably won't satisfy critics, but I'm liking the results so far. Can't wait to shoot portraits with it.

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Not bad, but highlights outlines are pretty rough. Impossible to evaluate sharpness at this image size.

Yeah, I have a feeling people will take note of that. I wonder how much is the lens, and how much of that is the result of post production (clarity sliders will cause outlines like that, for example).

Me? I couldn't care less. I don't sit and stare at out of focus lights.

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Re: XF56 f1.2 released and specs

dark13star wrote:

Krich13 wrote:

What is so damn important about number _per_unit_area_? I really don't get it. For all image quality purposes it's an irrelevant parameter.

Because that is an essential part of exposure. You can use a faster shutter speed.

No, you can use the same shutter speed, adjusting ISO accordingly for the same Image quality results.

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Re: XF56 f1.2 released and specs

Krich13 wrote:

malcolml1 wrote:

Yes, I follow your argument apart from one step which actually represents my original question:

>

For semiconductor sensors what matters is the total number of photons per photosite, pretty much regardless of the site area. Make two sensors: say an APS-S and FF ones both of say 16 megapixels. Expose them using the same scene for the same duration using 56/1.2 and 85/1.8 lenses respectively. Each photosite will receive the same NUMBER of photons (the number per unit area is 2.25 times larger in the first case, but the area itself is smaller by the same factor).

I agree with the area and scaling factor part, but my original question was whether it is true that the 56/1.2 will deliver the same number of photons per unit area on the APS sensor as the 85/1.8 lens on a FF sensor.

No, it will receive 2.25 times more photons PER UNIT AREA.

Totally agree that the 56/1/2 will deliver more photons per unit area than the 85/1.8 - and this is my question - if this is the case, how is the 56/1.2 equivalent to the 85/1.8 in terms of the light delivered per unit area - your statement above says they are:

"Make two sensors: say an APS-S and FF ones both of say 16 megapixels. Expose them using the same scene for the same duration using 56/1.2 and 85/1.8 lenses respectively. Each photosite will receive the same NUMBER of photons (the number per.."

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Re: XF56 f1.2 released and specs

malcolml1 wrote:

Krich13 wrote:

malcolml1 wrote:

Yes, I follow your argument apart from one step which actually represents my original question:

>

For semiconductor sensors what matters is the total number of photons per photosite, pretty much regardless of the site area. Make two sensors: say an APS-S and FF ones both of say 16 megapixels. Expose them using the same scene for the same duration using 56/1.2 and 85/1.8 lenses respectively. Each photosite will receive the same NUMBER of photons (the number per unit area is 2.25 times larger in the first case, but the area itself is smaller by the same factor).

I agree with the area and scaling factor part, but my original question was whether it is true that the 56/1.2 will deliver the same number of photons per unit area on the APS sensor as the 85/1.8 lens on a FF sensor.

No, it will receive 2.25 times more photons PER UNIT AREA.

Totally agree that the 56/1/2 will deliver more photons per unit area than the 85/1.8 - and this is my question - if this is the case, how is the 56/1.2 equivalent to the 85/1.8 in terms of the light delivered per unit area - your statement above says they are:

"Make two sensors: say an APS-S and FF ones both of say 16 megapixels. Expose them using the same scene for the same duration using 56/1.2 and 85/1.8 lenses respectively. Each photosite will receive the same NUMBER of photons (the number per.."

Where is the contradiction? Each photosite of the full frame sensor would have 2.25 times larger area (the same number (not density) of megapixels), number of photons _per_unit_area_ 2.25 times smaller, the TOTAL NUMBER of photons is the same. What is so difficult?

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Re: XF56 f1.2 released and specs

Asylum Photo wrote:

La Roque has a preview up:

http://www.laroquephoto.com/blog/2014/1/6/the-razors-edge-fujinon-xf-56mm-f12r

Probably won't satisfy critics, but I'm liking the results so far. Can't wait to shoot portraits with it.

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I read the review before Laroque removed it.   What I can see already from his shots is that 56/1.2 has a certain character and sure to become one of the famous lenses around.  I can see the character and it reminds me of another lens but I can't put my finger on what.    Perhaps something Leica-like in just how the lens is rendering?

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Re: XF56 f1.2 released and specs

Understand that fine...I was not really thinking about the pixel size. That is the bit I was missing. Just curious - do FF pixels typically have 2.25 times the area of APS ones?

I assume that if the FF pixels were the same size as the APS ones, then my argument would be correct (just so I can be sure I understand correctly).

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Re: XF56 f1.2 released and specs

Krich13 wrote:

No, you can use the same shutter speed, adjusting ISO accordingly for the same Image quality results.

Maybe on a Nikon FF, but have you seen how many Canon shooters here say they get better high-ISO results out of their Fujis? ISO must remain the same for the the comparison.

Now, if you had said that cameras with base ISO of 100 will get the same shutter speed as Fuji at 200, there would be some merit to the argument.

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Re: XF56 f1.2 released and specs
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Caerolle wrote:

I see this misunderstanding of exposure on the forum a lot lately. People need to go back to using hand-held light meters and setting exposures across multiple cameras to see that exposure is independent of sensor size. Depth of field will change at a given f-stop though.

I actually tested this a while back. I set my 1/2.3" sensor compact and my full-frame camera both to the same aperture and shutter speed, and the ISO was within 1 stop.

I too used to believe that the light gathering was changed by the factor of sensor size, but it is not so: at the same aperture, no matter the sensor size, the exposure is the same, give-or-take differences in the camera meters.

Exactly.  I can use a light meter to tell you the proper ISO, aperture, and shutter speed without knowing your sensor size.  This would be impossible if sensor size were a relevant variable in determining exposure.

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Re: XF56 f1.2 released and specs
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malcolml1 wrote:

Understand that fine...I was not really thinking about the pixel size. That is the bit I was missing. Just curious - do FF pixels typically have 2.25 times the area of APS ones?

Some do, some don't. Nikon's DF and D4 have 16 MP, just like the APS-C Fuji. Others, (D610, Sony A7, Canons) are around 20-24 MP, two others (Nikon D800E, Sony A7R) have 36 MP. On the other hand, recent Nikon APS-C cameras also have 24 MP, Samsung -- 20 MP -- so yes, pretty similar pixel count and hence the photosite area. Factor 2-2.5 area advantage for most FF pixels. Additional advantage of fatter picels that there is less of an area loss at the pixel edges.

I assume that if the FF pixels were the same size as the APS ones, then my argument would be correct (just so I can be sure I understand correctly).

No, it wouldn't, but for a different reason. Yes, in this case every pixel of an FF sensor would be noisier than that of an APS-C sensor, but the total number of pixel would be greater. Once you scale the larger image down (downsample) to the same size as an APS-C one, the noise of the final image would be similar again.

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Re: XF56 f1.2 released and specs

dark13star wrote:

Krich13 wrote:

No, you can use the same shutter speed, adjusting ISO accordingly for the same Image quality results.

Maybe on a Nikon FF, but have you seen how many Canon shooters here say they get better high-ISO results out of their Fujis?

One of the reasons I switched to Nikon was its (well, Sony's) better sensors. I heard the latest Canons (6D, 5DIII) are very good in low light, but I have no first-hand experience.

ISO must remain the same for the the comparison.

Huh? Why is that? For proper comparison ISO of the FF should be icnreased (compared to APS-C) by a stop and a little, and aperture set to its DOF-equivalent value. Shutter speed the same.

Now, if you had said that cameras with base ISO of 100 will get the same shutter speed as Fuji at 200, there would be some merit to the argument.

The other way around. What you can get on Fuji at ISO 200, you can get on Nikon at ISO 450. What you can get on Nikon at ISO 100... you can't get on Fuji at all (base ISO is 200).

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Re: XF56 f1.2 released and specs

Let us know how much to change for our 4x5 or 8x10 cameras. Would a banquet camera require more of your "proper" exposure? How about one of Maxwell Smart's spy cameras? Exposure is exposure, buddy.

I hope to see more of the 56mm, hopefully soon!

Krich13 wrote:

ISO must remain the same for the the comparison.

Huh? Why is that? For proper comparison ISO of the FF should be icnreased (compared to APS-C) by a stop and a little, and aperture set to its DOF-equivalent value. Shutter speed the same.

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Re: XF56 f1.2 released and specs

nalax wrote:

Let us know how much to change for our 4x5 or 8x10 cameras.

You can use tri-x w/o fear of grain - 35mm cannot.

How about one of Maxwell Smart's spy cameras?

Needs slow microfilm for decent grain when enlarged.

Exposure is exposure, buddy.

Yes, it is - and one of the constraints has always been noise vs. enlargement.

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