Understanding Macro designs and Macro vs Non-Macro distinction

[kumar_b]

<p>I will be buying the 40mm Micro Nikkor sometime soon. This will be my first real macro lens and I have thus been reading around to get the best out of it. So, here is a question for the experts. <br>

Is there something to quantify the extent to which macro lenses successfully correct for perspective distortion when up close ? Consider the following hypothetical scenarios for taking head shots (on DX sensors) : <br>

a) 40mm macro close to the subject vs 40mm non-macro at same distance - <br>

b) 40mm macro close to subject vs 85mm macro further from subject <br>

c) 40mm macro close to subject vs 85 mm non-macro further from the subject<br>

Let us assume that there is enough light that the possible difference in max appertures for macro and non-macro lenses is not a factor here. <br>

Now, my guesses are <br>

a) 40mm macro is better<br>

b) 85mm macro is better<br>

c) Not sure<br>

Am I right on a) and b ) and what is the best way to figure out the answer for c) ?<br>

I can ofcourse go to the nearest camera shop and shoot to observe the difference .But, I wanted to ask here anyway. <br>

Thanks in advance. This is my first post here.<br>

(I know this question might have relevance for non-Nikon owners as well. But, I could not find an obvious place for this question. Sorry if it is misplaced!) </p>

 

[JosvanEekelen]

<p>Hi Kumar, welcome to the forum.<br /> The main differences between macro and non-macro lenses are (1) macro lenses focus closer to the subject and (2) most or all macro lenses are flat field lenses, meaning that their plane of focus is flat i.e. a flat subject will be projected on the sensor/film as flat. In case of non macro lenses the plane of focus is more or less curved. This has nothing to do with perspective. In general the macro lenses will be better but this will mainly show up when your subject is flat, for instance documents. In other cases the difference will be small.<br /> My general advice with questions like this is not to theorize too much, start taking pictures and be happy.</p>

[kumar_b]

<p>I just realized this question is related to discussions in this thread : <a href="00ZHhl?start=40">http://www.photo.net/nikon-camera-forum/00ZHhl?start=40</a> and this posted it there I request one of the admins to delete this post. </p>

[kumar_b]

<p>Hi Jos, you were quick to respond. Thanks! <br /> (But, it is now wierd that I have ended up posting the question on two separate threads. Sorry about the confusion. Whats the etiquete for such scenarios ? Being able to delete one's posts atleast withing a few minutes of posting might help! )<br /> Is it just the flat fielding that is different in macros ? When I look @ the numbers from Nikon, what jumps out for me is that the min. focusing distance for the 40mm macro is half that of the 35mm non-macro. But, its max magnification is 6 times (as opposed to a naive doubling that one might have expected). So, it seems to me that a lot more is different in a macro lens design. And I completely understand when you say "shoot and be happy". That is what I plan to do. But, I am still curious about the theory. If you think this forum is not the right place for a technical response, you could point me to a reference where I can find more info. That would be fine as well.</p>

[jose_angel]

<p>Kumar, I`m not sure if you´re considering the loss of light due to the exceptional close focus ability of macro lenses:</p>

<blockquote>

<p><em>"Let us assume that there is enough light that the possible difference in max appertures for macro and non-macro lenses is not a factor here."</em></p>

</blockquote>

<p>Even with "enough light", the <em>effective aperture</em> in a macro lens could change. Well, with a non-macro lens, the minimim focus distance is limited, so you`ll not experience a (noticeable) change in the effective aperture.<br /> <br /> There are diferent macro lens designs, and with different optical tricks to do the work. Basically, they are lenses built into a telescopic barrel design that let them to extend far more than a "normal" lens, in order to achieve a shorter focus distance, hence magnification. Current designs achieve the very same effect -without-, or -with a shorter- (telescopic) barrel.</p>

[jose_angel]

<p>There is a nice article about lens basics (with some good references as well) in wikipedia:<a href="http://en.wikipedia.org/wiki/Macrophotography"> Macrophotography</a>.</p>

[alan_olander1664878205]

<p>Many macro lenses shorten their focal length as you focus closer. This would be one reason for the discrepancy between the minimum focus distance and the magnification of the 40mm macro vs 35mm.<br>

I, myself, would not buy such a short focal length macro lens as the 40mm; the working distance is too close.</p>

[joseph_smith3]

<p>You may find a few of the tutorials listed here to be relevant to your questions:</p>

<p><a href="http://www.cambridgeincolour.com/tutorials.htm">http://www.cambridgeincolour.com/tutorials.htm</a></p>

<p>Joe Smith</p>

[Robert DeCandido PhD]

<p>In Nikon world, micro is up to about 1:1...macro is 1:1 and beyond - so my guess is that you mean micro lenses by Nikon.</p>

[bebu_lamar]

<p>First Nikon uses the term Micro for Macro lenses. <br>

The definition of macro is a lens capable of focusing to 1:1 magnification.<br>

Usually macro lenses have flat field as compared to regular lenses. <br>

Before they started to make internal focusing lenses the aperture would changes with magnification and obey a fixed formula.<br>

Today with many lenses and macro lenses included have internal focusing you can't really use the lens extension formula any more because these lens shorten their focal length when they do close focusing.</p>

[nsfbr]

So you know, I couldn't imagine using a 40mm lens for macro work. It is just too short. I am sometimes frustrated with

my 105 (even though it is a spectacular lens) on a DX camera. Using a 40 would seem to be almost impossible.

[kumar_b]

<p>Thanks to everyone for the responses. After reading thro some of the links, I probably understand the macro designs a little better. Still, it would be great if manufacturers just gave a plot of the magnification as a function of focus distance. Or, maybe they do and I could not find it. If anyone has a link to such a plot for macro designs, please do share it. <br>

And I appreciate the concern of many that 40mm is way too short for macro. I don't plan on doing "serious macro". But, I think being able to get close enough to get bigger magnifications than 1:6 on a such a wide-ish lens is also a fun thing to do. Besides, this is very easy on my wallet :)</p>

[jose_angel]

<p>If I`m not wrong, there is a magnification/area of coverage/distance charts or something similar in the "instructions sheet" provided with each lens.</p>

[kumar_b]

<p>I just checked NIkon's manual. It has a plot for effective f-stop vs focus distance. I think one can indirectly infer the magnification from this. But, something more direct would have been nice. Is there some other instruction sheet available ? <br>

Another way to figure out would be to just play with the lens. It seems like the dial on the lens marks both distance and magnification ratios.</p>

[SCL]

<p>On topic, but different lens - I noted that the famous Kiron/Dine 105mm/ f2.8 macro lens (regardless of mount) user manual does list a chart of magnification ratios for each distance from the focal plane, along with the depth of field for each point at each marked aperture. I agree it would be nice if all manufacturers did this as a reference source.</p>

[kumar_b]

<p>Thanks, Stephen. Good to know that there is atleast one lens for which such data is provided. Is it accessible online someplace ?</p>