Can I use my APS-C kit lens as a reference for choosing between 50mm or 35mm prime lenses?

Question

I'm looking at getting a second lens in addition to my Nikon D7000's kit lens.

I want to know if it's possible to use my 18m-105mm kit lens to get an idea of the focal length for a 35mm lens vs. a 50 mm lens. If I set the kit lens at 35 and 50, will that give me an accurate idea of the magnification and field of view I would get with these two lenses?

I wanted to make sure this was correct, because I know there is a crop factor with a DX camera and I’m not sure if that is taken into effect with the kit lens or not.

So will the 50mm lens, when on my D7000, produce images like when I have my kit lens on the body set to 50mm? And, the same for the 35mm?

Answer 1

Focal length is focal length, regardless of sensor size or whether the lens is a zoom lens. If you have tried your kit lens at 35mm and 50mm, then the framing will pretty much be the same with prime lenses of those focal lengths. Prime lenses will offer a couple things your zoom lens does not, however.

For one, they should offer better quality, as prime lenses can be constructed to perfectly project the clearest image possible for the given focal length. There are degrees of optical quality within a given prime focal length, as a higher end lens will usually use better materials and lens elements. Generally speaking, though, primes offer better quality.

Second, prime lenses usually provide much wider maximum apertures. A 50mm prime can come in anywhere from f/1.8 through f/1.2, and older manual focus lenses may even be found with maximum apertures as wide as f/0.95. Wider apertures can be more difficult to use at times (due to extremely thin DOF), but they can provide some truly fantastic bokeh.

Regarding focal lengths on a cropped sensor, there is a fairly nice correlation between the 35mm and 50mm lenses and ideal portrait focal lengths on full-frame sensors. Nikon cameras have a 1.5x sensor crop factor. That means that a 35mm lens on an APS-C body "behaves as" a 52mm lens would on a full-frame body, due to the difference in the field of view captured by the APS-C sensor. The 50mm lens on APS-C behaves as a 75mm lens would on full-frame. As an additional lens, 85mm lenses behave like a 134mm lens on APS-C. These focal lengths fit pretty well with the ideal portrait focal lengths on full frame cameras, which include 50mm, 85mm, and 135mm.

It should be noted that 50mm lenses on 35mm film/full frame sensor produces a field of view that is very similar to the field of view of the human eye. The actual focal range for that falls between 45mm and 55mm.

So, given all of that...you can make the proper decision based on what you really want to capture. If you want to capture shots that have a relatively "normal" perspective similar to how the human eye sees, you might want to grab the 35mm lens. On a cropped sensor, it would behave like a 52mm lens. If you want a narrower field of view with smoother background blur, a 50mm or 85mm lens would give you that deeper DOF and narrower field, similar to 85mm and 135mm lenses on full frame, respectively. Finally, if you want to capture a wider field of view than the human eye, or want to get really close and capture a lot of perspective, you could get a 24mm lens, which, intriguingly, behaves like a 36mm lens on full frame.

The beauty of primes is their field of view, or effective focal lengths, are easy to translate between APS-C and Full Frame. If you take the common prime focal lengths of 14mm, 24mm, 35mm, 50mm, 85mm, and 135mm as used on full frame, you can pretty much simply "shift" them up by one place to arrive at the effective focal length ranges on APS-C. The exact focal lengths on APS-C, for reference, are: 21mm, 36mm, 52mm, 75mm, 134mm, 202mm. So long as you understand that about 50mm is the same field of view as "normal" perspective, it is fairly easy to determine which focal length to use to get the field of view/perspective you want in your photographs.

Answer 2

The field of view on the same sensor will be the same for 35mm on a prime or 35mm on a zoom, that's not specifically related to the crop factor unless your talking different cameras as well which you're not.

As for buying a 35mm or a 50mm, I'm of the camp that every camera bag should have a "nifty fifty" in it. So, I would be going for the 50mm before a 35mm, but that's just a matter of personal preference.

Answer 3

No, the crop factor is not taken into account. There will likely be a small amount of error on the focal length indicator, but it'll be accurate enough for comparison. Given your recent questions, though -- particularly, the emphasis on people photography -- you'll probably find the 50mm more to your liking than a 35mm lens, particularly since you can get a Nikkor 50mm/1.4 lens for about the same price as a 35mm/2.0 -- that's a stop faster, a lot more suitable for typical portrait framing, and capable of giving both narrower depth of field and faster shutter speeds at the same light level and ISO settings.

Answer 4

Yes, that's accurate, but instead of taking sample shots, why don't you analyze the shots you've already taken? Make a graph of all your favorite (i.e. the ones you've kept or uploaded or e-mailed) pictures (using the EXIF data embedded in each file), plotting focal length vs. count-of-focal length. Then just look for peaks. If the majority of your photos are at 18mm, splurge on an ultra-wide (10-22 or thereabouts) lens; if they're near 35, 50, or 85mm then buy the appropriate fast lens; if they're all at 105 then treat yourself to a 135/2.8. After all, if less than 5% of your favorite photos are in the 30-60mm range, you wouldn't want to buy a 35mm or 50mm lens: you'd never use it!

Answer 5

You can also consider 28mm as a standard prime lens for walkaround as it is closer to the "theoretical normal", however, it is not as good as 50mm for portraits. I have both 28mm 1.8 and 50mm 1.4. 28mm is my walkaround lens when I go on business trips or close quarter concert/club photography. As it is already a bit narrow for snapping a beautiful room or building, or even a group of people in a smaller room, I wouldn't want to use a 35mm as a walkaround. And to get yummy portraits where you can see the strands of hair and smooth creamy bokeh I use the 50mm 1.4. I wish they'd make a 18mm 1.8, too.

I feel no longing for a 35mm at all, as it is one step back with my 50mm or one step forward with my 28mm.

Take your kit lens and try it, and note how little difference it is from 28 to 35 and from 35 to 50 and then just take one step back and forth.

So yes, you can use your kit lens as reference to see how each prime would feel regarding the framing. Keep it at 28mm all day, see how that feels, next day try 35mm, next day 50mm, then maybe extend you test to 85mm .