Enlarging lenses for macro

Dan Fromm said:

Please see post #4 in this thread. Then ask the moderators to delete your post #19 and this one. What you said in your post #19 is pure nonsense.

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There are four statements in my post #19 please share with us which are those you believe incorrect.

Looking back at your post #4 I believe we are both saying the same thing, you wrote "To take best advantage of the lens' optimizations (large front, small behind) the lens should be reversed when used at magnifications greater than 1:1." This is what I stated in a different fashion, reverse the lens when magnification is in the range 2x - 10x.

Take care with your hostile attitude to other posters, you could make enemies.

Enlarging lenses are optimized for enlarging, just as taking lenses are optimized for taking.

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Actually they can be used with the exact same performance characteristics for reductions.

It depends on the magnification and the lens.

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Actually, the performance characteristics for an enlarging lens that dictate optimum resolution when the front faces the larger angle of view are independent of focal length. It is, in fact, independent of lens magnification. A modern enlarging lens of 300mm [low magnificaton] and 50mm [high magnification] share the same characteristics with respect to which side should face larger angle of view.

Ted, since you asked me to parse I'll parse.

I think there is a simple way to understand this question.

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True.

An enlarging lens has a range of enlarging ratios for which the lens is designed to operate, for example 2x to 10x.

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Lens-specific but the idea is correct.

When the lens is used to generate images in the magnification range intended by the maker then it gives best performance when reversed so that the distance from the "bottom" of the lens to the film plane is larger than the distance from the "top" of the lens to the object being photographed.

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What do "bottom" and "top" mean? This statement is incomprehensible.

One way to keep this concept straight in the mind is to recall that when the distance from the lens to the object and from the lens to the film plane are the same the magnification ratio is 1x. When the distance from the lens to the film plane is more than the distance to the object the magnification is a positive number in proportion to the ratio of the two distances, and is equal to film plane distance divided by object distance.

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Are you a native speaker of English? I ask not to insult but because the statement I quoted is far from idiomatic. It is stilted, reads like a poor translation.

Front node to subject distance = f*(m+1)/m, rear node to subject distance = f*(m+1). Rear node to film distance/front node to subject distance is indeed magnification.

Nothing you wrote mentions lens' symmetry. Symmetrical lenses, for example symmetrical type Apo Nikkors, don't have to be reversed when used at magnifications above 1:1. And you present a rule of thumb or a law given from on high instead of explaining that with an asymmetrical lens optimized for working at magnifications below 1:1, reversing the lens when using it above 1:1 preserves the optimizations and gives better image quality than using it facing normally.

That's better

Bottom and top refer to enlarger lenses used in their original application, in a vertical enlarger.

Regret my English is not to your liking, calling this nonsense seems extreme.

I defined the conditions in my first line, magnification is 2x to 10x, that is the realm of the typical enlarging lens used in amateur darkrooms. Some may have professional experience using 1:1 ratio process lenses, however the thread title is "enlarging lenses used for macro", not "process lenses used for macro" which would require different answers. We are discussing the use of lenses to make images having magnification greater than 1.

Symmetry is the province of the lens designer not the lens user, the user choses the lens by its focal length, aperture and intended magnification range. An asymmetrical lens optimized for working at magnifications below 1:1 is not an enlarging lens, this seems irrelevant to the topic in hand, this topic is about enlarging lenses.

I could be wrong, but I think we agree, surprisingly since you described my post as nonsense, that an enlarging lens (2x to 10x) when used for macro work (which is by definition greater than 1:1) is best reversed.

Dan Fromm said:

It depends on the lens. Some of Schneider's enlarging lenses have cells that are direct fits in #00 or #0 shutters. Reversing these lenses is easy, just screw the front cell into the back of the shutter and the rear cell into the front of the shutter. . . .

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According to data on the S. K. Grimes site, the diaphragm in many shutters is net centered between the front and back lens cell mounts. Reversing lens cells in this situation can cause a loss of performance. It certainly did when I tried to reverse the cells of a Optar 90mm WA.

Jim Jones said:

According to data on the S. K. Grimes site, the diaphragm in many shutters is net centered between the front and back lens cell mounts. Reversing lens cells in this situation can cause a loss of performance. It certainly did when I tried to reverse the cells of a Optar 90mm WA.

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That probably has far more to do with using a wide angle lens for macro work, and as the Optar is a Symmetrical lens it doesn't need reversing. Don't believe all you read on the Grimes website.

Ian

tedr1 said:

<snip> Symmetry is the province of the lens designer not the lens user, the user choses the lens by its focal length, aperture and intended magnification range. An asymmetrical lens optimized for working at magnifications below 1:1 is not an enlarging lens, this seems irrelevant to the topic in hand, this topic is about enlarging lenses

<snip> I could be wrong, but I think we agree, surprisingly since you described my post as nonsense, that an enlarging lens (2x to 10x) when used for macro work (which is by definition greater than 1:1) is best reversed.

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Symmetry most certainly matters for users.

You confuse magnification when printing (print 2 - who-knows-how-many times larger than negative) and when working in photomacrography (image on negative >1 to who-knows-how-many times larger than subject).

You also don't know that there are many asymmetrical enlarging lenses. All tessar type enlarging lenses, e.g., Schneider's Comparon series, are very asymmetrical. Comparons perform well as enlarging lenses and as taking lenses in the range 2:1 to 6:1. Some plasmat type enlarging lenses are perfectly symmetrical, e.g., some (not all) Boyer Saphir Bs, others are not, e.g., some (not all) Boyer Saphir Bs.

You're not completely right. Some enlarging lenses that perform superbly as macro lenses, e.g., the 50/4.5 Enlarging Ektar, are perfectly symmetrical heliar types. Because of their symmetry they don't have to be reversed for use above 1:1.

Where we really part company is why and under what conditions reversing any lens, be it intended for enlarging or taking at normal distances, when using it for photomacrography (magnification > 1) is a good idea.

I am about to finish my 11x14 inch glass late enlarger.i already have my 11x14 inch glass plate camera finished .it is a reflex camera I have t stand on a chair an view the image screen . Right is left and left is right but it's right side up..my lens I a 300 mm f .4.5 lomo lens .I read a members contribution to enlargeing and found out what I needed to know. Excellent members here. 200 white LEDs on a 13 x 17 inch board is located 8 inches behind my 11x 14 glass plate Ina standard that moves from 9 inches to 20 inches. The lomo 300 mm lens is reversed the lens see a well lite negative the lens projects that to a movable 44x56 inch frame that holds my prepared coated canvas.my developer is rodinal and another goody that gives me platinum looking prints ASA is approx. 3 .lens is fast and negative for projection is super bright. i am aware that lots of intense light on a grain tends to keep the grain small and longer exposures tends to make that grain grow. All this information I have discovered over the years .I mention these facts as all I have learned from sites like yours and my collection of 100 year old manuals.now I'm ready to dump my 760 mm Nikon nikkors and other modern equipment and travel the western states taking pictures like Matthew brady

When http://www.coinimaging.com/macro_lens_tests.html did their tests, they found that some enlarging lenses benefit from reversing, but a few do not.

The two I own, a Rodenstock 50mm APO and a Schneider 28mm f/4 both seem to benefit from reversing on a PB-4 bellows.

Dan Fromm said:

It depends on the magnification and the lens.

Magnification: enlarging lenses are made to have a small negative behind the lens and a large print in front of it. This is parallel to the usual taking lens situation where there's a small image behind the lens and a large subject in front of it. Enlarging lenses are optimized for enlarging, just as taking lenses are optimized for taking. So, if the magnification is less than 1:1 the lens should be used as intended, i.e., facing normally. If magnification is greater than 1:1, then there's a small subject in front of the lens and a large image behind it. To take best advantage of the lens' optimizations (large front, small behind) the lens should be reversed when used at magnifications greater than 1:1.

Lens: some enlarging lenses, for example 50/4.5 and 75/4.5 Enlarging Ektars (heliar types), are perfectly symmetrical. They can be used facing normally at all magnifications. Reversing them doesn't hurt, but it is a bother. Others, for example Schneider Comparons (tessar types), are quite asymmetrical. They should be used facing normally up to 1:1 and reversed above 1:1.

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+1