Reverse Macro

[deaner66]

<p>I got a lens reversal adapter off Ebay for my K10D, and it came today. I've messed with it a little tonight, and I have a few questions for anyone who has used an adapter like this.</p>

<p>I used it with my SMC-M 50mm 1.7 and tried using it with my SMC-M 135mm 3.5.</p>

<p>The first thing I noticed is that focusing doesn't work. Not visibly, anyway. The only way I could get a subject in focus was by adjusting the distance from the camera to the subject.</p>

<p>This is rather disappointing and eliminates a lot of things you can focus on. And it is a pain in the rear, especially when using a tripod. Anything that moves, it would seem, is out of the question.</p>

<p>The focus distance from the lens is 5 1/2 inches from the subject.</p>

<p>I couldn't get anything in focus with the 135.</p>

<p>My questions:</p>

<p>Why doesn't the focus work? After all, the lens is moving, changing what the sensor sees, but it doesn't seem to affect anything through the viewfinder.</p>

<p>Am I missing something here, or is this just the limitation of this adapter?</p>

<p>On the positive side, when anything is in focus with the 50, it is in very tight, very crisp and looks great at 100% crop.</p>

<p>And it only cost $8.</p><div></div>

[deaner66]

<p>A CD shot.</p><div></div>

[deaner66]

<p>My desktop weight.</p><div></div>

[deaner66]

<p>Skin</p>

[deaner66]

<p>redo</p><div></div>

[joseph_wisniewski]

<p>Your 50mm f1.7 is not moving when you turn the focus ring. All the optic parts are firmly attached to the reverser, and only the barrel (non-optic) is moving.</p>

<p>The classic method for focusing in that situation is to use a tripod and a device called a "focusing rail" that lets you crank the camera back and fourth. Those cost about $90.</p>

[jpo3136b]

<p>I don't use a reversal ring, but I use bellows; when I do, the focusing ring will make a slight adjustment; slight. Really, in macro, the normal focusing will be more of a magnification refinement than a focusing action. You may be able to adjust magnification slightly to include or exclude something from your field of view; but, it's normal to not be able to really focus with it. Changing distance to subject is the primary focusing method. </p>

<p>For the different lenses, I have experienced something similar with bellow. For example, my strongest magnification comes from a 55mm 645 lens on a bellow. A wider angle lens, the 645 35mm, does not. I could go through a list of lenses; but the point is that particular lens, with the way the elements are organized inside it; that element organization has a lot to do with how it performs macro functions. Grouping goes so far as to be able for me to employ a 80-160 telephoto, even though they are supposed to be "unusable." Well, they're usable, it's just that the zoom function doesn't behave as it would during normal telephoto use. </p>

<p>The internal design of the glass will affect how well the lens handles macro, and also reversal. </p>

[donnie_strickland]

<p>Ditto what Joseph said. You need a focusing rack/rail.</p>

<p> </p>

[andrewg_ny]

<p>To put another way--when a lens is mounted in the normal way, zooming and focusing may vary the distance between the film plane and the rear elements. Depending on the lens design, when you change the focus on a reversed lens the elements may stay in the same place but only move the reversed lense's mount which would have no effect.</p>

<p>Even with a dedicated macro lens, critical focus at close ranges is often largely done by varying the subject distance rather than using the focus ring.</p>

[deaner66]

<p>Thanks for the comments and advice. Now I'm wondering how much different an actual macro lens is from this reverse adapter. Obviously, a macro lens WILL change focus. But I've never used a macro before. How effective is a macro at normal shots?</p>

[snik75]

<p>Fine, except for a long focus throw. Makes AF slow in lenses that have it, and makes for nice manual focussing.</p>

<p>The best relatively cheap route to macro is extension tubes. You can get a set off eBay for less than $20. They are far more flexible than the reverse ring. Peter Zack has a nice post on macro options on Misere's blog, "Embracing the Light". Google it and check it out if you are interested!</p>

[andrewg_ny]

<p>Blog is actually <a href="http://enticingthelight.wordpress.com/2009/02/26/shooting-macros-section-3-the-math/"><em>Enticing</em> the Light</a> .</p>

[jeff_livacich]

<p>As you've noticed, reversing the 50mm yielded much closer focusing. A lens reversed on the camera will have to be focused by moving back and forth slightly; easy when hand holding.<br>

The great benefit of reversing is on tubes or bellows, where extension is greater.<br>

Think of how a light ray travels through the lens. The 50mm is designed for optimum quality at or near infinity, and the image will degrade some as the lens is focused closer, away from optimum. At infinity, the image-forming rays enter parallel to each other and converge as they leave the lens in order to bring the image into focus on the image plane (i.e., the film or sensor). At closest focusing distance, the image-forming rays entering are significantly divergent, therefore not optimal, but not enough to compromise image quality much.<br>

If the lens is extended enough on tubes or bellows, the compromise becomes more pronounced. At large subject to image plane distances (normal focusing range), the distance from the subject to the front element is much larger than the distance from the rear element to the image plane. As focusing distances get closer the ratio decreases more and more. Reversing the lens restores balance to the optical equation, allowing rays to travel through the lens more like they were supposed to, just in reverse direction. They enter and exit each element at an angle closer to optimum, therefore with less image degradation. Results can be quite good, especially for the cost. The biggest negative is loss of auto diaphragm function.<br>

Bellows give more adjustability as to exact degree of magnification. They are bulky and harder to manage than tubes, while tubes leave you with one fixed focal point with a reversed lens. Another thing you can try is a 49mm to 49mm macro coupler, which connects your 135mm and your 50mm front to front by their filter threads. This employs the 50 as a highly corrected diopter lens on the front of the 135. A fun, cheap and effective method which yields good results, and retains focusing ability on the 135mm.<br>

Macros yield the best results. They are designed to have a flat field, very low distortion, and excellent resolution. Their high optical quality helps them perform well even at infinity. The longer ones are usually recommended for greater working distance, but the 50mm ones are very usable. They're smaller, lighter, and need less extension to get to higher magnifications.</p>