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5-Oct-2008, 05:16
Sorry for asking what might seems a dum question.

I know that bellows increase in size when subject lens plane are close, at what stage do you expect this to happen, I.e using 150mm lens and subject is 3 feet away, and at what distance is 1:1 ratio.
Also do you expect focusing as this stage to remain sharp?

Does the same bellows increase happen with a dedicated Macro Lens, if not what are the advantages of a macro lens other from an optical qulality for closup.

Thanks

Dan Fromm
5-Oct-2008, 08:31
A few useful magic formulas:

extension (from the infinity position) = (1 + m) * f

effective aperture = aperture set * (1 + m/p) for a lens mounted normally

effective aperture = aperture set * (1 + mp)/p for a lens mounted reversed

m = magnification (size of image on film/size of subject)

f = lens' focal length

p = lens' pupillary magnification (diameter of entrance pupil/diameter of exit pupil); many people ignore this but it is a killer for very asymmetric lenses, e.g., telephoto and retrofocus

lens type/optimizations have no effect of extension given magnification and focal length

focusing closeup is pretty easy because the depth of field is so thin

lenses optimized for closeup ("macro" lenses) have only one advantage closeup over lenses optimized for distance: better image quality closeup.

There are some very good books on this topic. Buy and study Lester Lefkowitz' The Manual of Closeup Photography. And learn to spell dumb.

Ernest Purdum
5-Oct-2008, 08:37
At 1:1 subject/image ratio, you are extended two focal lengths and the subject is two focal lengths from the lens.

When you are close to 1:1, trying to focus by moving the lens just changes the size of the image, not the focus. You need to focus by moving the whole camera or the subject.

Dan Fromm
5-Oct-2008, 09:32
Ernest, it is a fine point not very relevant to the OP's question, but all magnifications except 1:1 have an, um, sister magnification with the same film plane-to-subject distance. One switches from one sister to the other by moving the lens without moving the camera.

Here's a pair of sisters: 1:2 and 2:1. With both, film plane-to-subject distance is 4.5f + the lens' internodal distance.

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5-Oct-2008, 11:33
A few useful magic formulas:

There are some very good books on this topic. Buy and study Lester Lefkowitz' The Manual of Closeup Photography. And learn to spell dumb.

Thanks Dan - I realised the typo as soon as I pressed the submit button, however my excuse is that after all English is not my first language.

Thanks

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5-Oct-2008, 11:43
At 1:1 subject/image ratio, you are extended two focal lengths and the subject is two focal lengths from the lens.

Hi Ernest

What about on 1:2 and 1:5 Subjet/Image ratio, what size should Bellows be and subject distance to lens

Thanks

Dan Fromm
5-Oct-2008, 11:44
Use the magic formulas. Plug in magnifications (1:5 = 1/5 = 0.2) and focal length.

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5-Oct-2008, 11:49
Use the magic formulas. Plug in magnifications (1:5 = 1/5 = 0.2) and focal length.

Ok that is for the bellows, what about subject to lens distance is that 1.2 x focal length too

5-Oct-2008, 12:33
A few useful magic formulas:

...
There are some very good books on this topic. Buy and study Lester Lefkowitz' The Manual of Closeup Photography. And learn to spell dumb.

Why do you make this very helpful post almost all the way through and then throw on a gratuitous comment on the end?

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5-Oct-2008, 12:44
Why do you make this very helpful post almost all the way through and then throw on a gratuitous comment on the end?

Hi Pirate Robins

I did not take it personally, as I knew how to spell dumb, I suppose I should proof read before submitting, that is something I should get into the habit of doing.

I suppose Dan could have phrased it better, but that how this worls works.

Dan Fromm
5-Oct-2008, 12:59
Why do you make this very helpful post almost all the way through and then throw on a gratuitous comment on the end?If you can't be helpful, don't post. And don't abuse those of us who are helpful.

Dan Fromm
5-Oct-2008, 13:02
Ok that is for the bellows, what about subject to lens distance is that 1.2 x focal length tooAnother magic formula:

front node to subject distance: f * (m + 1)/m

Exactly where the front node is depends on the lens. For most of the lenses used for LF photography, it is a little in front of the diaphragm.

Patrik Roseen
5-Oct-2008, 13:45
Now, talking about 'dumb' questions (it is actually 'dum' in my native language)...

I have not given this much thought, but here goes. What is really the working principle of my 'macro-converter' I have for my 35mm camera (which also works as a 2xteleconverter). How should one view this set of lenses in relation to the lens attached to it, and what is the resulting focal length and lens to film distance etc.

Has there been any such system for Large Format?

Peter K
5-Oct-2008, 14:13
Diopters as the "Proxar" and "Distar" from Zeiss or "Xenar-Vorsatzlinsen" where aviable also for LF-lensens. This lenses are nothing other than eye-glasses. Of course the resolution with such a system, lens and diopter, isn't the same anymore. Also the effective aperture changes together with the total focal-length of the lens + diopter. So the exposure time has to increased or decreased.

Dan Fromm
5-Oct-2008, 15:01
Patrik, the macro-converters I've seen -- I have a t-mount Vivitar one made for their 450 solid cat -- combine a teleconverter with a focusing helical or are an extension tube with a removable teleconverter inside. With the former, the helical can be used to add extension. The latter can be used as a simple extension tube when the glass is removed.

AFAIK no such things have been made for LF. I mean, the standard responses to running out of extension when shooting closeup with LF are to add extension (more rail, extension bellows, ... ) or to use a shorter lens. Think of which, how did your 17 Tominon work out?

When we put a 2x TC behind a macro lens, as for example my 200/4 MicroNikkor AIS, the aperture (set and effective) is halved and focal length is doubled. Lens-to-subject distance, given magnification, is also doubled. My 200/4 goes to 1:2 on its own mount, to 1:1 on a 2x TC.

Peter, I don't think Patrik was asking about supplemental lenses. I could be mistaken, but I think he meant the devices I described.

Cheers,

Dan

Y'know, yesterday the dread pirate Robins, a gang of avian thugs that live in my neighborhood, flocked 'round our bird feeder until my wife shooed them away.

Ernest Purdum
5-Oct-2008, 18:31
The tele conversion units for 35mm are very close optically to the variable focal length units which were the original telephoto lenses before the Busch Bis-Telar fixed focal length telephoto lens came along. Most of the variable units were used behind a prime lens which could vary in design as much as between a Dallmeyer portrait and a Ser.VII Protar. With these units you weren't restricted to the 2x or maybe 3X of the 35mm units, you could adjust most of them up to ridiculous extremes. They might have been a little better if they had been made for only one magnification.

I don't know how many typos of mine still exist here on the Forum because I didn't find the edit capability until fairly recently.

seawolf66
6-Oct-2008, 08:56
Hey in my book DUM or DUMB are the same only difference is DUM less to type

Peter K
6-Oct-2008, 10:59
Hey in my book DUM or DUMB are the same only difference is DUM less to type
Be careful Lauren, the spell of big Dan will hit you :D

Dan Fromm
6-Oct-2008, 12:39
Peter, I make an exception for Lauren. Gotta conserve my energy ...

Patrik Roseen
7-Oct-2008, 10:59
Patrik, the macro-converters I've seen -- I have a t-mount Vivitar one made for their 450 solid cat -- combine a teleconverter with a focusing helical or are an extension tube with a removable teleconverter inside. With the former, the helical can be used to add extension. The latter can be used as a simple extension tube when the glass is removed.

AFAIK no such things have been made for LF. I mean, the standard responses to running out of extension when shooting closeup with LF are to add extension (more rail, extension bellows, ... ) or to use a shorter lens. Think of which, how did your 17 Tominon work out?

When we put a 2x TC behind a macro lens, as for example my 200/4 MicroNikkor AIS, the aperture (set and effective) is halved and focal length is doubled. Lens-to-subject distance, given magnification, is also doubled. My 200/4 goes to 1:2 on its own mount, to 1:1 on a 2x TC.

Peter, I don't think Patrik was asking about supplemental lenses. I could be mistaken, but I think he meant the devices I described.

Cheers,

Dan

Y'know, yesterday the dread pirate Robins, a gang of avian thugs that live in my neighborhood, flocked 'round our bird feeder until my wife shooed them away.

I have tried using the Tominon 17mm a few times and the lens does what it is supposed to. It's just me who needs to get more practise using it.

Jeff Keller
7-Oct-2008, 15:45
Horseman made a 2x converter which was intended to be used with their 150mm lens. It mounted on the back of the lens, inside the bellows, and didn't have a helicoid. I'm not sure whether it worked for their 4x5 field cameras or just their 6x9.

When you think about the lack of any standards for the rear element diameter of a LF lens and similar lack of fixed spacing from filter threads to rear element glass, it is surprising that a 2x converter would exist.

For 35mm SLRs, in addition to the matched macro focusing converter for the Series 1 450mm f4.5 catadioptric, Vivitar made a nice macro focusing 2x converter in many different SLR mounts.

Jeff Keller

Patrik, the macro-converters I've seen -- I have a t-mount Vivitar one made for their 450 solid cat -- combine a teleconverter with a focusing helical or are an extension tube with a removable teleconverter inside. With the former, the helical can be used to add extension. The latter can be used as a simple extension tube when the glass is removed.

AFAIK no such things have been made for LF. I mean, the standard responses to running out of extension when shooting closeup with LF are to add extension (more rail, extension bellows, ... ) or to use a shorter lens. Think of which, how did your 17 Tominon work out?

....

Cheers,

Dan
.

Dan Fromm
7-Oct-2008, 16:29
Jeff, y'know, people say good things about the Vivitar Matched Magnifier for their 450. It may work very well behind that lens. It isn't that wonderful behind my Questar 700.

Cheers,

Dan

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9-Oct-2008, 00:33
Thanks Dan for your formula and to all

Got myself a new book "View Camera Technique" by Leslie Strobel which is excellent and makes a good companion to Steve Simmons book.

Now down to absorbing the book.