How Much Magnification Is This?

<p>I'm in the market for a dedicated macro lens, or some combo of gear that can produce results at very least as good as what I currently have. What I currently have is simply D.I.Y close-up filters that fit on the end of my lenses, and the one I use most of the time for ease of use is my Nikkor 18-55mm. Sometimes I'll use them on my 55-200mm lens but I can't use any of the zoom because it makes the image look horrible. They only work good at around 40 - 60mm.<br /> <br />So I was hoping some kind soul could tell me what kind of magnification I am getting with my filters, and to put that in terms of macro lenses.</p>

<p>Here is the filter, and some test shots with it on.<br /> http://www.photo.net/beginner-photography-questions-forum/00asIo</p>

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

<p>This is the closest focusing distance at 55mm with the nikkor 18-55mm</p><div></div>

What is the size of your camera's sensor?

<p>Here is my latest shot the filter. The image has been cropped a good bit, but still has decent size at 1555 x 1042 pixels.</p><div></div>

<p>Mike, the camera I am using now is the D5100 with a sensor size of 23.6 x 15.7 mm. Those were all from my D40X which is 23.7 x 15.6mm, according to Dpreview.com. </p>

To calculate the magnification, divide the width of the sensor by the width of whatever is included in the full frame image. In the examples above, it looks like the magnification with the filter is about 0.98x (23.7 / 24.2) and without the filter it's about 0.38x (23.7 / 62).

<p><em>"it looks like the magnification with the filter is about ..."</em></p>

<p>... 0.694x, or 1:1.44.</p>

<p>(You dropped 10mm Mike D.) ;-)</p><div></div>

Ooops. I actually did measure the extra 12.2 mm, but dropped ten of it when adding. I really shouldn't answer questions before finishing my morning coffee.

<p>It would be easier if you photographed the ruler with the markings all the way across, i.e. "0" at the left edge of the frame.</p>

<p>So in respects to dedicated macro lenses, what am I looking at here? Lower than normal magnification? Standard? I can spend maybe $600 on one, so would one give me more magnification?</p>

<p>Hats off to Michael Freeman, I get about the same, magnification 0.7. I rounded up because there are many variables in these measurements but 0.7x is close enough.</p>

<p>Hats off to Matt Murphy - you fabricated a magnifying glass from the hardware store and made a first class supplemental close-up lens. We mount these to fool our camera into thinking the subject is further away than the focusing mechanism will accommodate. You did a wonderful job. Normally such a lash-up will induce optical problems like color flinging but your images are tack sharp.</p>

<p>As I said, your lash-up yields a magnification of 0.7x. That means an object 10mm long will image on your sensor as being 7mm long. If you obtain magnification 1 (unity or 1:1), a 10mm object would image 10mm or life-size.</p>

<p>Now most camera lenses are optimized to image distant objects. A macro lens is optimized to image at life-size. Now most macro lens image 1:1 however some magnify more.</p>

<p>When it comes to extreme close-up work, you can purchase a set of close-up lenses. These are available is various strengths and they can be stacked to gain more magnification. Cameras with interchangeable lenses can benefit from a set of rings. These are spacers that fit between the lens and the camera body. The further the lens is moved from the sensor, the more the magnification. To obtain life-size, the lens is racked forward one focal length. Thus a 55mm lens is spaced 55mm more forward. You can also buy a special attachment that features leather bellows and allows the lens to be super extended. With a bellows extension you can achieve magnified views like 2x or 3x or more.</p>

<p>Best would be a marco lens that fits your camera. These are easy to use and deliver life-size images. They also may accept close-up lenses, spacer rings and bellows. </p>

<p>Anyway, have fun, shoot lots of close-up's.</p>

<p>Why thank you Alan, and thank you all for helping! This is why I come here. The results are usually what I need. I was really hoping for 1:1 or more though. I'm wondering if stacking filters will increase the magnification. Like the one I used for this project, I have a few more that are just the 52mm ring. Either way, my second one I made a week ago from my old binoculars is even better. The magnification is still somehow the same, but the glass is coated, and it has less barrel (?) distortion and less chromatic aberrations. It also is scratch free.</p>

<p>I do have a decent film macro rig, but I'm afraid to use it. It is a Pentax ME Super with an 80-200mm lens, a 135mm, and a 28-50mm. I also have a 2x Macro converter, and 3 extension tubes. Mix it all together and you can almost see plant cells, if the plant is literally touching the lens. The flashes I have are also alright with diffusers and light funnels.</p>

<p>I'm scared to use it at its full macro potential because the manual focus is crazy irritating at that level, the exposures require flash and I don't know how to use the one flash with the exposure dial, and I am afraid that if I used flash, I would have whole rolls of out of focus, incredibly over-exposed bugs. Or under exposed. Either way.</p>

<p>Most macro lenses do at best 1:1, because they can also focus to infinity (extension tubes can get you close to 2:1 with some lenses). Canon has an excellent dedicated macro lens that goes from 1:1 to 5:1 (MP-E 65mm). It's manual focus only, and the barrel extends when increasing magnification. It's also a bit pricey, running $1100.</p>

<p>It can be tricky to find your subject at 5X, since the working distance gets very short and DOF is so shallow, you can be aiming right at your subject and not know until you get the lens to the proper distance. Macro rails help tremendously at this magnification.</p>

<p>I don't know if Nikon has an equivalent lens, or if an adapter can be used to mount it on a Nikon.</p>

<p>What a wonderful project, making your own supplemental close-up lenses. OK to do any meaningful calculations, you need to know the focal length of the lens you are mounting. Take the lens outside along with a tape measure and image the sun, you know, like a burning glass. Measure the distance center of lens to focused image of the sun. This measurement will be the focal length. We always measure using a far distant object because nearby subjects will focus at an expanded lens to target (focal plane) distance. Opticians use a point source placed some distance away. The source is called an artificial star.</p>

<p>Now close-up lenses are sold as inexpensive lens fabricated from a single piece of glass. These will yield an uncorrected aberration, a color fringing around the subject. Actually, this is the result of each color coming to a focus at a slightly different distance lens to focal plane. We correct this by sandwiching two glass elements together. One is a strong positive (convex) and the other a weak negative (concave). The two elements are different density glass; they have opposite chromatic aberrations that nearly cancel each other. The binocular objective is such a lens known as an achromatic (Greek without color error).</p>

<p>Once the focal length is known in millimeters (25.4mm to the inch), prefix a 1/ in front. Say you measure 666mm lens to image of sun, then 1/666 or 1 ÷ 666 = 0.0015. Now multiply by 1000: thus 0.0015 x 1000 = 1.5. This value 1.5 is the power of the lens expressed in a unit called diopter. The diopter unit is favored by opticians because it eases the burden of the math needed to figure revised focal length when lens elements are combined. To calculate the outcome of mounting the 666mm supplement atop your 55mm lens, both are expressed in diopter and added together thus:<br /> 55mm = 1/55x1000 = 18.2d<br /> 666mm = 1/666x1000 = 1.50d<br /> The two combined are 1.5 + 18.2 = 19.7d<br /> Now we convert 19.7d back to millimeters thus<br /> 19.7 ÷ 1000 = 0.0197 and 1/0.197 = 50.8mm.<br /> The total of the lash-up is 50.8mm<br /> You can combine two or more supplemental lens and sandwich these atop your camera lens.<br /> Add two 666mm supplemental to 55mm camera.<br /> 18.2d + 1.5d + 1.5d = 21.2d<br /> Convert to millimeters<br /> 1 ÷ (21.2 ÷ 1000) = 47.2mm</p>

<p>Now the focus distance to an object with the camera set to infinity ( ∞ ) is the same as the power of supplement.<br /> Add a 666mm to a 55mm and the camera will focus tack sharp if set to ∞ and the object is placed 666mm in front of the lens.<br /> Add two 666mm, the combined is 1.5d + 1.5d = 3d = 1/3 x 1000 = 333mm meaning the camera now focuses when set to infinity, tack sharp, on an object 333mm distant.<br /> The total system with two 666mm supplements<br /> 18.2d + 1.5d + 1.5d = 21.2d total<br /> Convert to millimeters 1/ (21.2 ÷ 1000) = 47.2mm</p>

<p>If the camera focus is shifted in manual to focus at 1 meter (3 foot) on the footage scale, this is the equivalent of adding 1 diopter more power to the system.</p>

<p>More gobbledygook from Alan Marcus</p>

<p>I am definitely not an engineer, so I have no idea about what magnification you are getting, but your shots look OK to me.</p>

<p>A dedicated macro lens is ultimately the best answer; but, as already suggested and as shown by your own examples, there are lots of perfectly acceptable ways of getting there with cheaper alternatives.</p>

<p>"We correct this by sandwiching two glass elements together. One is a strong positive (convex) and the other a weak negative (concave). The two elements are different density glass; they have opposite chromatic aberrations that nearly cancel each other. The binocular objective is such a lens known as an achromatic (Greek without color error)."</p>

<p>Alan, would this piece of glass describe what you are talking about? It is part of my second close-up filter, and it is 2 pieces of coated glass, with varying levels of roundness, and it is from a pair of binoculars. Or if it doesn't, what about stacking the other eye piece on top of it, or stacking my other filter on top of this one?</p>

<p><img src="http://static.photo.net/attachments/bboard/00b/00bSDT-525753584.jpg" alt="" width="700" height="464" /></p>

<p>Your binocular objective (pictured) is an achromatic doublet lens made by cementing two lenses together. When light enters the lens, its path is changed by the shape and density of the glass. The binocular objective causes light rays to converge taking on the shape of an ice-cream cone. Should you use it to make a burning glass; you will be focusing an image of the sun on a target like a white piece of paper. The image of the sun forms at the apex of the cone. The surface of the lens collects the light rays forcing them to bend inward. This concentrates the light and heat of the sun at the apex of the cone. The distance lens-to- sun's image is the focal length. Sunlight is a mix of all colors of the rainbow. Sorry to report that the lens bends each color differently, each color will have a different cone length. Thus, each color comes to a focus at a different distance from the lens. We see this as a color fringe around an image. We call this color error a chromatic aberration.</p>

<p>The best solution is to fabricate a compound lens. Your binocular objective is an achromatic doublet. We credit Chester Moore Hall, an English telescope maker in the 18th century with constructing a telescope objective using a combination of dense crown glass and light flint glass. His design mitigated color fringing. </p>

<p>Now the surface of the lens is polished glass. As you known, polished glass also acts like a mirror as you can see your reflection as you stand before a glass window. Because of this, each surface of a lens reflects about 3% of the light away. This can be devastating as camera lenses are complex. Many glass lenses of different shapes and density of glass are needed to mitigate optical errors called aberrations. The polished surfaces reflect away light and the lens can suffer a 25% or more loss. Worst, inside surfaces re-reflect light causing lots of stray light. This misdirected light comingles with the image forming rays and degrades the final image. To mitigate we need to somehow reduce the amount of light reflected away by the shiny glass.</p>

<p>The solution was discovered by the English optician, Harold Taylor. He observed that old lenses passed more light than new lenses. Except for age, they were exactly the same but the old lenses had a "bloom". This is a tarnish caused by air pollution. England's industry was powered by steam made by burning coal. The coal soot contained gasses that etched the surface of glass. This filth coat was thin, however, it reduced surface reflections. Today we artificially age lenses by coating them with a thin layer of silicon dioxide or fluoride or the like. It’s the thickness of the coat that reduces reflection. A modern lens may have 8 or even 12 coats each a different thickness. You see, each color reflects and each is optimized by a different coat thickness.</p>

<p>Coating to control surface reflections and combining lenses to migrate aberrations is a precise science. You are unlikely to succeed at doing this yourself, but who knows, you might become the next Mr. Hall or Mr. Taylor and discover how to make a better lens. You could get a Nobel Prize.</p>

<p>Alan, excellent info. I'm still digesting it. Would you say that the 2nd piece of glass pictured above is superior to the glass on the 1st filter, being coated and having two parts, as opposed to the other which is just one piece of uncoated glass? I think it should, considering the 2nd is from a pair of Bushnell binoculars and the other is from a cheap magnifying glass. I've tested the 2nd Bushnell one and so far it seems to produce less yellow fringing, and slightly more contrast. The out of focus "bokeh" is also sharper, and I'm not sure if that is a good thing or not. Sounds like it is though.</p>

<p><br /> Both work excellently as burning glasses, mwuahaha. Lucky for the bugs, I'm using them as lenses and not death rays.<br>

<br /> Also, what about adding a polarizing filter to equation? Would that help reduce chromatic aberrations by reducing glare and reflections?</p>

<p>The objective lens from the Bushnell binocular is the superior lens to use as a supplemental close-up attachment. Your homework was to use the lenses as a burning glass and report the focal length. A polarizing filter is used to mitigate reflections from surfaces like glass or water etc. The polarizing filter deepens blue sky causing clouds to standout in bold relief against the sky. A polarizing filter will not reduce chromatic aberrations. All filters add shiny glass surfaces that reflect light plus a super high quality filter is flat glass both surfaces parallel to each other. Therefore, all filters not being perfect will degrade the image. We mount filters only when the benefit outweighs the mischief. </p>

<p>Ok so here is the final result! I placed the glass on its center of gravity on the flattest surface I could find, slid the plastic encasing from the binoculars over the top and spun the glass on its center to make sure it was on there evenly, and it was. Then I did the same with a rear element lens cap with a hole drilled into it. Then, I attached the metal ring from a broken IR filter of mine to the back, placed it on my D5100 with live view on, made some final adjustments, and sealed the lens with super glue. The extra plastic on the front acts as a necessary hood to keep light out. </p>

<p>I'm not done with the aesthetic part of it. I need to either carefully wrap it with electrical tape, or spray paint it to get blemishes out and and to even out the superglued look. </p>

<p>NOW. I need further help. When this is placed on my 55-200 mm lens, the closest focus is 3 inches, and the maximum distance is 5.5. When placed on my 18-55mm, the closest I can get is 1 inch, and the farthest is 6 inches. What I need to know and can't seem to wrap my head around at the moment is which is better, or more practical. With the 55-200, I get greater magnification, it doesn't block my built in flash, and I have more distance between me and the subject - so lesser chance of it getting scared and flying away. </p>

<p>On the other hand, the 18-55mm seems to have more working space so I don't have to move the camera around so much to focus, and since it gets closer to the subject, but with the same magnification as the closest focu on the 55-200, I figure it has more detail. I'm not sure of that, as I don't know if a few inches is as dramatic in macro as 10s of feet are with regular lenses. <br>

<br />Anyone? I'm so close to getting this all down, and I can't do it without this sites expertise. Thank you in advance. I'm off to work. </p><div></div>