Purchasing Nikon 24-120mm F4 FX lens on Nikon D7100 DX camera, opinion please

Started 4 months ago | Questions thread
EcoPix
EcoPix Regular Member • Posts: 303
Summary: Nikon 24-120mm F4 FX lens for D7100 DX
3

Let’s quickly summarise this confusing thread for people coming to this pertinent topic. I’m sure we’re all talking about the same lens – we can reserve blame on Nikon’s quality control for when it really matters!

I feel as if I’m volunteering for dpReview here, but one takes pity on anyone trying to make sense of this discussion. There’s a lot of assumed knowledge underlying it that newcomers may not have.

AF-s Nikkor 24-120mm f4 ED VR FX lens for DX use:

This is a full frame zoom lens with a relatively fast f4 constant maximum aperture that can be used also on DX format, on which its range is from semi-wide angle (approx. 36mm equivalent film/FX) to medium telephoto (approx.. 180mm film/FX equivalent).

Advantages

- complements the kit lenses by avoiding the need to change lenses in the short telephoto/portrait range;

- cheaper than other Nikkor lenses that offer the same lens speed and focal lengths;

- effective image stabilisation;

- high-end lens coatings to increase contrast where light sources may induce flair;

- relatively fast at the longer focal lengths compared to DX kit lenses;

- better corner sharpness than many DX kit lenses due to larger image circle;

- usable centre sharpness throughout, and good sharpness over most focal lengths and apertures;

- good colour and tone if viewed in isolation (not compared to other lenses, and can be largely adjusted in post);

- can also be used as an FX lens.

Disadvantages

- larger and heavier than some DX-only lens options that bridge the kit lens portrait interchange;

- slightly slower than most DX lenses at the short end;

- less sharp at f4 and f5.6 than many Nikkor lenses for critical applications such as large prints or heavy cropping;

- noticeably less sharp than many Nikkor lenses at focal lengths above 100mm;

- tonal rendition noticeably poorer than many Nikkor lenses if compared side by side at large sizes;

- lower sharpness in periphery at f4 than many Nikkor lenses;

- slightly slower at a given aperture than some Nikkor lenses;

- generally more expensive than many DX-only slow zooms.

Compared to the AF-s Nikkor 18-140mm f3.5-5.6 ED VR DX lens

The 18-140mm is Nikon’s current DX solution for a single slow DX zoom lens that covers wide angle (approx. 27mm equivalent film/FX) to medium telephoto (approx. 210mm film/FX equivalent), and can be used for most of what the 24-120mm can be used for on DX format, with the notable exception of low light/fast speed telephoto.

Advantages of the 24-120mm over the 18-140mm:

- can also be used for full frame images on FX;

- approx. one stop faster at long focal lengths (e.g. 1/250th instead of 1/125 in low-light sports);

- sharper corners at many focal lengths and apertures.

Disadvantages of the 24-120mm compared to the 18-140:

- absence of wider focal lengths 28mm to 35mm film/FX equivalents;

- slower at shorter focal lengths;

- larger and heavier for the focal range offered;

- slightly shorter maximum focal length (180mm compared with 210mm film/FX equivalents);

- slightly less sharp in central part of image overall;

- noticeably less sharp at long focal lengths;

- tonal rendition slightly poorer if compared side by side at large sizes;

- more expensive, at least new.

AF-s Nikkor 24-120mm f4 ED VR FX lens on Nikon D7100 and other high res DX bodies

Issues

The D7100 is DX (APS-sized) with a 24 megapixel sensor approximately 23mm wide, with no diffusing filter. As such it is a very high-resolution body that is more demanding on lens performance than many Nikon bodies, including the FX format cameras for which the 24-120mm is designed.

This difference can be expressed by ‘pixel pitch’- the number of sensing photo sites per unit length or unit area. Megapixels is a proxy measure of this by expressing total number of photo sites over the whole sensor.

The (very) approximate megapixels of example Nikon bodies over the DX area are:

D300 – 12mp

D7000 – 16mp

D7100 – 24mp

D610 (cropped to DX) – 10mp

D810 (cropped to DX) – 15mp

One can see that the D7100 ‘looks more closely’ at the lens’ projected image than other commonly used Nikon bodies, and therefore slight variations in overall projected image fidelity can be more apparent on the D7100 (and other 24mp DX bodies).

In other words, FX cameras are ‘kinder to lenses’, or less demanding on overall lens image quality, than current DX bodies. Partially offsetting this is the crop – DX bodies only record the middle area of the FX lens’ imaging circle, so poorer peripheral areas of an FX lens are irrelevant to a DX body.

Results

At large print sizes, small crops, or 100% screen view of full resolution images, the D7100 will show more of the 24-120mm’s optical shortcomings (in the image’s middle area) than other cameras. This could manifest as a general lack of crispness in fine detail, muddiness of fine textures, or slurred detail in any in-focus peripheral areas of the image.

Once the image is downsized for normal use to megapixels comparable to other cameras, these faults can become unimportant to the effectiveness of the image. Optical shortcomings are also normally less important than blurring due to subject or camera movement.

Use of this lens on DX therefore comes down to a personal decision based on use and needs.

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