Why does the max aperture change when use Nikon 60mm AF-D Micro on D90 camera?

Question

I have found that my Nikon 60mm Micro AF-D changes aperture from 2.8 to 3.2 when used with a D90. I have tried both A and M mode. Is it by design? Why?

I intend to buy Nikon 50mm 1.4 AF-D, but it also has a switch on the lens and it will lock the maximum aperture at 2.0 (my guess) instead 2.8. So should I buy it or not, or would it be better to buy the newer 50mm 1.4 AF-S version?

Asked by Ngan Pham

Answer

I think you must have noticed something slightly different. The max aperture is a function of the lens and should be unaffected by camera.

The Nikon 60mm Micro AF-D will change its maximum aperture as a function of the focus distance. As it focuses closer, the reported max aperture drops. By life size 1:1, its down to f/5.

There is apparently a button on the 50mm AF-D that will lock it to its minimum aperture. This is a property of manual aperture lenses. Modern cameras control the aperture automatically from the camera body. Setting this switch locks it at the minimum aperture so that the camera can automatically control it. Since your camera has an in-body focus motor, you're able to use the AF-D or AF-S, you just need to decide if there's a difference for the price that you care about. They'll both take great pictures, the AF-S will just focus faster and quieter mainly.

Answered by rfusca

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Max aperture change when use Nikon 60mm AF-D Micro on D90 camera

Question

I found my Nikon 60mm Micro AF-D change aperture from 2.8 to 3.2 when I use it with D90. I was tried A and M mode. It's by design? but Why?.

I intend to buy Nikon 50mm 1.4 AF-D, but it also have a switch button on len (http://www.kenrockwell.com/nikon/5014af.htm) and it will lock maximum aperture at 2.0 (my guess) instead 2.8. So I should buy it or not, or should buy a newer 50mm 1.4 AF-S version?.

Asked by Ngan Pham

Answer

I think you must have noticed something slightly different. The max aperture is a function of the lens and should be unaffected by camera.

The Nikon 60mm Micro AF-D will change its maximum aperture as a function of the focus distance. As it focuses closer, the reported max aperture drops. By life size 1:1, its down to f/5.

There is apparently a button on the 50mm AF-D that will lock its minimum aperture. Many lenses are soft wide open. Locking out the wide open aperture prevents the camera from auto selecting a softer aperture. Since your camera has an in-body focus motor, you're able to use the AF-D or AF-S, you just need to decide if there's a difference for the price that you care about. They'll both take great pictures, the AF-S will just focus faster and quieter mainly.

Answered by rfusca

Check more discussion of this question.

Does the Nikkor 50mm f/1.4g perform better than the f/1.8d?

Question

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?

Answer

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.

Check more discussion of this question.

Does the Nikkor 50mm f/1.8d perform better than the f/1.4g?

Question

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?

Answer

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.

Check more discussion of this question.