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Looking into these two lenses, I'm getting the impression that for my Nikon D-90 with DX camera sensor that the f/1.8d would waste light that is cropped by the sensor whereas the f/1.4g would not as it is designed for the DX style. Further, the f/1.8d is not available as AF-S whereas the f/1.4g is AF-S.

Is my analysis correct and thus the f/1.4g will perform better with the DX style camera?

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7 Answers 7

up vote 8 down vote accepted

The Nikon AF-S 50mm f1.4 G is not designed for the smaller DX sensor and has the same image circle as the 1.8

Are you thinking of the AF-S 35mm f/1.8 G DX which is designed for a smaller sensor compared to the AF-S 35mm f/1.4G?

In any case the size of the image circle is of minor importance to the light gathering ability - only the aperture matters, as Evan states.

Despite a lens designed for a smaller image circle letting in less light total, it lets in the same light per unit area, so if you swap one lens for another designed for a larger image circle, but the same f-stop then your exposure would be the same.

The previous paragraph ignores vignetting, or the tendency for brightness to fall off across the frame. This usually gives lenses designed for a larger image circle a brightness advantage. There are other advantages to using lenses designed for the sensor you are using, such as sharpness, weight and better resistance to flare.

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Stating that image circle is not important flies in the face of my common sense thinking about this. If light is missing the sensor, how can you not be getting less than the full use of the lens? How couldn't a 50mm with dx sized image circle and same f-stop not have more light hitting sensor than a regular 35mm sized image circle for same 50mm and f-stop? –  WilliamKF Dec 5 '10 at 23:53
1  
@WilliamKF Think about it like this - cropping the middle of a photo doesn't make it any darker, despite the fact that less light makes up the new cropped image. Now imagine you take the image circle of a 35mm lens and then concentrate all that light down to a smaller image circle. The image will get brighter, yes, but now you've changed the focal length and so the f stop has changed! This is easy to verify using two lenses with the same focal length, f stop but different image circles. Take two images with the same shutter speed and they will be the same brightness. –  Matt Grum Dec 6 '10 at 0:16

I've owned and used both. I sold my 1.8, and wish now that I hadn't because it's not better/worse - just different. Step back, and look at the bigger picture:

The IQ on these two are just different (at least below 2.8).
Consider the 1.4g because it:
1. doesn't require an in-camera motor to auto-focus.
2. has different coatings/and aperture blade design. (In my opinion) The 1.4g has a smoother bokeh, and seems to have improved color contrast and saturation.
3. is a little faster (1.4 vs. 1.8) - and you'll use it.
4. has that MA/M switch - I use it.
5. has improved weather sealing (? verify this)
6. has a quiet autofocus

Consider the 1.8 because it:
1. is about $300 cheaper
2. has very nice IQ, and maybe sharper compared to the 1.4g ... do some research online.
3. has an aperture ring - you can use it on older camera bodies. Can't do that with the 1.4G mount.
4. can be mounted backwards and used as a macro.
5. Seems faster to autofocus (but louder).


If you're like me, you'll be very happy with both.

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Most of the lens give their best at f8. Both f/1.4 and f/1.8 are very good lens, I don't expect to notice any difference between them in the "normal" range (from f/2.8).

So the question is: "is the range f/1.4-f/1.8 worth of the price difference?"

For me the answer is YES I took very nice picture using the ultra shallow dof and the nice bokeh.

It's also useful for dark scenes, but considering the current VR technology I think a f/2.8 VR lens would be a better choice.

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By the way: the AF-S 50/1.4G has more silent AF then the older 'normal' AF version, but it is not faster (rather the opposite).

I was quite disappointed about the AF speed of my AF-S 50/1.4G and had to learn the 'S' does not stand for 'Speed' but for 'Silent' instead.

For the rest the 1.4G is a very nice lens.

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DigitalRevTV did a review and found the 1.4G to have a smoother milker bokeh where the 1.8D was sometimes a bit odd. The 1.4 was found to be sharper also. That said they also tested a Sigma 1.4 which was found to be the best of the 3.

Youtube link: http://www.youtube.com/watch?v=pfyrGfqZQ-A

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One issue I heard many times about F/1.4G version is that on wide aperture (1.4) when shooting something with backlight of the sun it gives some anomalies, like blue spots on the middle of the picture. But not all the lenses produce this issue. So better to test it in that mode before purchase (F1/4 and point a camera on a subject with the sun as backlight)

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The f/1.4g will perform better simply because it has a wider relative aperture (f-stop), not because its image circle is smaller.

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Stating that image circle is not important flies in the face of my common sense thinking about this. If light is missing the sensor, how can you not be getting less than the full use of the lens? How couldn't a 50mm with dx sized image circle and same f-stop not have more light hitting sensor than a regular 35mm sized image circle for same 50mm and f-stop? –  WilliamKF Dec 5 '10 at 23:55
    
@WilliamKF you get less light total with the DX sensor but the same light per unit area, thus the same exposure. –  Matt Grum Dec 6 '10 at 0:18

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