Check my math...?

[philip_wilson]

<p>Martin</p>

<p>As many have said the 100mm lens will be a 100mm lens angle of view on a full frame nikon and will have the 1.5 crop factor on a DX format. If you do go down this route consider a tilt / shift adaptor. I use a Mirex Tilt shift adaptor with Mamiya M645 lenses. This combination works very well (especially on full frame) and I get 35mm and above TS lenses for the price of an adaptor. The IQ is very high but I do need live view as they can be hard to focus and tilt.</p>

<p>In terms of the oft cited lens resolution issue There may not be as much in it as people think. Here is a link that shows tests of 80mm lenses - the Mamiya 80 F1.9 and f2.8 do very well arguably out resolving the Leica 85 f1.4 and Nikon 85 F1.4. Even the Pentax MF lens out resolves the Nikon 85 F1.8.<br>

http://slrlensreview.com/web/benchmarks-resources-131/119-85mm-challenge/459-85mm-challenge-leica-vs-nikon-vs-mamiya-645-vs-pentax-645-part-2.html</p>

[andylynn]

<p>You want a 100mm manual lens on a Nikon, get a Series E 100mm f/2.8. It will cost next to nothing and you'll be surprised at how good the image quality will be.</p>

[q.g._de_bakker]

<i>"As many have said the 100mm lens will be a 100mm lens angle of view on a full frame nikon and will have the 1.5 crop factor on a DX format."</i><br><br>To avoid confusion: it will be a 100 mm lens on DX format (and any other format) too.

[zack_zoll]

<p>The largest benefit to "new" lens technology, aside from AF speed, is not in the pro lenses, but the cheap ones. Nano coatings, etc. correct for colour and CA, but most "pro" grade lenses have very few issues with this anyway. For a very long time Nikon didn't even use ED glass on their top-level prime lenses that where 35-100mm because it 'wasn't necessary,' such as with the 85mm f/1.4D that performs VERY similarly to the G/ED/Nano nersion.</p>

<p>The only place where there has been a huge improvement of non-AF performance over the last 20 years has been the cheap and/or kit lenses, where better coatings and better camera/lens chips allow lens makers to correct for uses caused by making lenses cheaply.</p>

[ken_max__parks]

<p>The focal length of a MF lens, such as a Hassy 80mm (Zeiss) will change when adapted for a 35mm and/or DSLR (ACP-S). Even more so on an Olympus E-3. The 80mm equaled to that of a 200mm on the Olympus DSLR. This was verified with the viewing of a 70-300mm lens, tested corner to corner for sizing in the viewfinder. Also, this comes out to a magnification of 2.5x.</p>

 

[q.g._de_bakker]

Once again, <b>the focal length remains what it is</b>.<br>When put on a 35 mm camera or a small-sensor DSLR, any medium format 80 mm lens produces the same image as any other 80 mm lens.<br>If your test would show that it produces the same image as a 200 mm lens, either your test is seriously flawed, or you mix up things in the presentation of the test, or (very likely) that 200 mm you mention isn't 200 mm, but someone's made-up 'equivalent focal length'.

[ondebanks]

<p>Ken"MAX",<br>

You've bought into the common error of equating "crop factor" (using a smaller sensor/film) with "focal length multiplier" (increasing the focal length of the lens).</p>

<p>The only way to actually increase the focal length of a lens is to add more glass - e.g. put a diverging lens behind it, like a teleconverter. Merely putting a lens on a smaller-sensored body does not add any more glass, so as Q.G. says, <strong>the focal length remains what it is</strong>. The <em>only</em> thing that changes is that you capture a smaller area of the image projected by the lens, and that smaller area <em>corresponds to</em> the field of view of a longer focal length lens. It is not, however, produced <em>by</em> a longer focal length lens! A real longer focal length lens would produce that same field of view - but over a much larger image area, with higher magnification (smaller angle per mm of sensor) and higher resolution.</p>

<p>For example, that 80mm Hasselblad lens on a 645 medium format digital sensor (same 4:3 aspect ratio as the Olympus Four-Thirds sensor, so it's a valid comparison) gives the same image, in terms of field of view and composition, as a 25mm lens on an Olympus DSLR. The "crop factor" is 3.2x in this case, and if one were being tongue-in-cheek, one could say that "the Olympus lens has an <em>effective focal length</em> of 80mm, using 645 as a reference format". But the medium format setup will resolve 3.2x more detail in each axis, if the pixel sizes are equal (and they are almost identical in the 8.3 Mpix Olympus E300 and the 80 Mpix PhaseOne/Leaf medium format backs: 5.4 micron and 5.2 micron respectively); and the information content of the medium format image will be 10.3x higher than that of the Olympus! This should clearly illustrate that "effective focal lenght" is absolutely not the same as focal length. The Olympus 25mm lens is just a 25mm lens, and it cannot perform as anything other than a 25mm lens. By the same token. the Hasselblad 80mm lens is just an 80mm lens, and it cannot...well, I think you get the rest.</p>

<p> </p>

[q.g._de_bakker]

Perhaps in one sentence:<br><br>If you put a <b>[FILL IN THE FORMAT OF YOUR CHOICE = a]</b> lens of <b>[FILL IN THE FOCAL LENGTH OF YOUR CHOICE = F]</b> mm focal length on a <b>[FILL IN ANOTHER, OR THE SAME, FORMAT OF YOUR CHOICE = a]</b> camera, <i>it produces the same image</i> as a <b>[F = THE FOCAL LENGTH YOU FILLED IN BEFORE]</b> mm focal length lens made for that <b>[FILL IN ANY FORMAT OF YOUR CHOICE = a]</b> camera.<br><br>Note that variable <b>a</b> is completely irrelevant (or a, a' and a'' if you are uncomfortable with using the same variable name for something that is completely irrelevant). You can fill in anything you like without it changing anything to the tautological essence of the above sentence, it being: <b>F = F</b>.<br>From that tautology <i>"it produces the same image"</i> follows.