D600 with AI (non-CPU) prime lens

<p>I recently brought the Nikon D600. As a seasonal photographer this camera does good job for me, especially I can use all my AI prime lenses I used for my film camera. Yesterday I tested my old 35mm f/1.4 with the camera. Everything works fine except, when I use aperture f=1.4 I see dark corners, which, become less and less when I lower the aperture. The problem seems not there when I try other lens with longer range, i.e. 85mm f/1.4<br>

<br />Does anyone know the reason? I suppose the fx camera acts (in terms of coupling with lenses) the same way as traditional film camera. Why are there dark corners?</p>

 

<p>It's <a href="http://en.wikipedia.org/wiki/Vignetting">optical vignetting</a>, which the 35 f/1.4 Ai/AiS is pretty good at (mine sure is). It's part of the lens design, and some lenses show it quite a lot (in my collection the 35 f/1.4 and 24-120 f/4VR are the worst), others hardly at all (i.e. 105 f/2.5, 50 f/1.8G). Indeed it gets less when stopping down.<br /> On DX cameras, you will not notice with full frame lenses as that part of the lens is not used. But DX lenses (created to only cover the smaller sensor area) can show the same 'defect'.</p>

<p>It's probably a combination of light fall off from lens and light hitting the sensor at an oblique angle at the periphery. A lens will project a larger image circle at smaller apertures which will brighten up the corners as you so witnessed.</p>

<p>This is a "contradiction"-<br>

the wider the aperture, the more likely there is to be vignetting. Some lenses are especially prone to the problem which may have been relegated to secondary importance by over-riding goals in the design (widest possible aperture, for example).</p>

<p>It can be usually be easily corrected in ACR or in Photoshop proper (<strong>Filter</strong>><strong>Lens Correction</strong>).</p>

<p>Thanks for the responses. Does this happen in traditional film cameras as well? I did not notice it on my old FE2. Maybe I just did not do experiment on film so I missed the effect. Just want to confirm that I can do nothing to avoid this with camera settings. Am I right?</p>

<p>The D600's auto correction can fix that, but it may not know enough about that old lens to do so automatically. So, you have to do that in post.</p>

<p>This happened with film cameras too. Its all part of the optical properties of the lens.</p>

<p>It may have been less noticable on film: most of the reason is to do with less light reaching the sensor, but some of it is that light falling on the sensor at oblique angles doesn't "fall into" the sensors so effectively. Some modern lenses are designed to improve this somewhat. Film is less sensitive to the angle at which light hits it (which is why it's easier to design a film rangefinder than a digital one). In the large format world, there are centre filters that you can put on a lens to compensate for the light fall-off. You can fix it in software, with the proviso that there's less light hitting the edges of the frame so you lose a bit of dynamic range. Nothing's broken, at least.</p>

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<p>Does this happen in traditional film cameras as well?</p>

</blockquote>

<p>Yes, although as said, in real life (natural scenes and the like) it is rarely very objectionable. <br>

It is a lens characteristic/contradiction having to do with the path light takes out toward the edges.</p>

<p>One additional aspect is that digital sensors may be a <em>little more</em> sensitive to the angle of the light coming in from the lens than was the nearly 2-dimensional film.<br>

At least this is what the lens makers have suggested with their new "digital" lenses.</p>

<p>There's nothing mysterious about vignetting. It's very easy to see the reason just by looking through the back of a lens and swivelling it from side to side slightly. The effect is less with longer lenses because their cone of projection has a smaller angle as seen from the focal plane.</p>

<p>The diagram below shows how and why the average lens vignettes at full aperture. It simply lets in less light at the sides and corners of the image.</p><div></div>