DaveyDitzer Loc: Western PA

As I add lenses to my Nikon Df kit, I am faced with a choice of buying a very good 105mm lens or using my mediocre 70-300 mm lens. In situations where 105 mm is not enough, I'd have to crop a fair amount; whereas I could fill more of the frame with zoom, recognizing that the final quality may not be a sharp. Would I loose more detail in the cropped photo or the one shot with the zoom, ceteris parabus (all else being equal)?

JimH123 Loc: Morgan Hill, CA

Another factor to consider is the f-stop value being used. Most lenses are somewhat, or a whole lot, soft at the wide end. And in most cases, even kit lenses are sharp when stopped down enough. Although if stopped down too far, diffraction starts to enter into the equation.

But as for your question, if you take a picture with the 105mm, and then crop that image so that it is the same as the field of view as something from the 70-300mm lens, you have several things happening to be aware of.

1. The 105mm image is going to be throwing away pixels and you are left with something from the middle of the image with fewer pixels.

2. The 70-300mm has greater resolution due to the greater magnification and will end up with more pixels.

3. The effect of this is that the 105mm may indeed start out sharper and the 70-300mm start out softer. But in the end, the lack of pixels will take its toll on the image. For example, you may have something like a leaf close to the subject. With the 70-300mm, perhaps the leaf is 20 pixels wide. And perhaps with the 105, it is 10 pixels wide, or perhaps 5 pixels wide. The 105 may be sharper, but it also is working with less detail. I am going to guess that the long focal length 70-300 is going to win this struggle over the shorter focal length 105mm lens.

DaveyDitzer Loc: Western PA

Thank you. Very helpful and coherent reply.

jcboy3

If you buy the 105mm, then you have the very good 105mm for when it is the best choice, and the 70-300mm when it is the best choice. A little experience with both lenses will let you know when each is good.

But it is unlikely that the 105mm would replace the 300mm zoom.

selmslie Loc: Fernandina Beach, FL, USA

I got a good 75-300 f/4.5-5.6 AF (1981) from KEH for only $133 in 2013. It has a little chromatic aberration at 300mm but it's quite sharp.

Last year I got a 300mm f/4.5 AIs (1986) from KEH for $228. It's much sharper than the zoom and it has no apparent CA.

Both lenses are about the same size and weight and they work fine on my Df. The zoom is convenient but when I need 300mm I use the manual focus prime lens.