jerry2

Johnathan... I hate to rain your parade, but I think your explanation is not true. Here is why, my Nikor 1200 tele needs about 780mm of bellows. Following your reasoning, the 420mm of saved extension is relocated by a relocated forward lens nodal point. 420 mm is about 17"... there is no way this can be true, the total lens is not nearly this long. Sorry....

 

Unfortunately the best explanation I have, is the one I presented before. The optical design of the lens allows for a shorter infinity focus. After that, it's pay as you go! To further my position, think of this.... even though my Nikor 1200 tele focusses at infinity at almost half the distance vs. a normal lens, I get no benefit of extra light at infinity focus on the gg! This too flies in the face of common sense. It's obvious the optics are consuming an extraordinary amount of light to accomodate for the desired goal, less bellows draw, right?

 

Also, if my explanation is not true, then tele lenses would violate the light meter / f stop relationship! When you take a light meter reading, the result never asks if your using a tele, or non tele lens. So lens designers must be certain to get the same amount of light on the gg at infinity focus, regardless of the lens type used. So in essence, a tele lens is a compromise, it provides shorter infinity focus but at the same time, it does not deliver the extra light that one would expect. (but would not want, so as to preserve the f stop / light meter relationship.)

 

 

YOu wrote.... Thank you Bill and George, your logic is impeccable and I don't need tests and wasted polaroids to prove what I know makes sense,

 

This violates one of photography's greatest myths, if it makes sense, you don't have to test! I would run the test like I described, it only takes 10 minutes and it wastes no film at all, just point a spot meter on the center of the gg. Then inform us all what you have learned! I admire you tenacity Johnathan! Teles fall into a black hole of photographic literature!

Johnathan, sorry I have not followed your thread....from your previous post... you wrote...

 

> Bill et al,......that is what is giving me problems, I thought about that when considering the original calculations, but then again the lens focuses at infinity @ 152mm and not at its own Focal length of 270mm,

 

That is correct, hence why the lens design is called a tele lens vs. a normal lens - it is optically designed to focus at infinity with less distance between nodal point and film. But keep in mind, it's still a 270mm fl lens.

 

> so how can another 270mm extension be two stops?

 

This is beauty of the telephoto lens. You get one free pass (shorter bellows extension than expected), but it's at only at infinity.

 

 

> Maybe I'm not seeing it, but ala the inverse square law everything is figured from a starting point of 152mm or 6 inches where the lens focuses @ infinity,

 

This is very true of NORMAL lenses. This is what differentiates teles vs. normal lenses. But your thinking is very clear here, I too stumbled on this for quite awhile when I first start using teles.

 

> twice the distance from there is 12 inches.

 

Yes, but this is a rule you just created. The tried and true rule is..... with any lens....increase the bellows ext. one fl after focus at infinity, add two stops compensation! When I first using teles, here is how I learned to accept this. Try this test.... focus at infinity, then point the camera at a white wall, put spot meter on center of gg, take EV reading. Then increase REAR extension (to avoid changing lens to light distance) an amount equal to the fl of the lens. Re check the gg with the light meter, voila, 2 stops. This worked for all my teles. Have you tried this yet? It might make you accept it, but still not understand it.

 

On this post you wrote.... My question to George et al, is does this method make sense? Is there an easier way to do it?

 

I can't imagine it getting any easier than what I described. Unless of course it does not work. If it does not work, it will be the first tele lens that failed this test. But I will never be too confident of anything in this field! BTW, the discs work fine also, to me, its just more math to do with teles, with normal lenses the disc is very fast assuming your shooting subjects are close enough to see the disc easy enough on the gg.

 

> But we dont need to know the actual focal length in order to make an extremely accurate bellows extension chart for any particular lens! All we need to know is the magnification and the pupillary ratio!

 

Knowing the magnification ratio is just a back door approach to knowing the additional extension. For example, .0001 magnification ratio is equivalent to focussing at infinty, for any fl lens. (But I personaly think its easy to focus at infinity and mark the rail or distance between two points than constantly struggling with this approach?) A 1:1 magnfication ratio equals bellows extension of infinity focus distance, plus one fl. It's that easy. You just discovered a more complex back door approach.

 

> The focal length of the lens is irrelevant! The focal length of the lens is irrelevant!

 

It's not irrelevant, you are arriving at the fl through the pupilary ratio, six of one, half dozen of the other.

 

> Put the lens (for which you have already determined the pupillary ratio) on your camera, and mark a 4 inch line on the ground glass.

4 inches times 0.1 magnification equals 40 inches. So adjust the camera and lens so that an object exactly 40 inches long is reduced to the 4 inch line marked on your ground glass. Be sure its in focus.

Now go to the chart and find the f-stop adjustment for your lens pupillary ratio at the .1 setting.

 

What you describe above is still a lot of work, but it will get you to the same place in the end. I still think the easiest arrangement for all lenses is as follows. In your case with the 270 tele, lets say the distance between your two standards when focussed at infinity is 150mm. With this information, you simply make a cheat sheet for each 1/3 of a stop, then each time you focus, just measure the distance between the standards (in the same place of course) for example....

 

1/3 stop = 183mm

2/3 stop = 219mm

1 stop = 262mm

1.33 stop = 308mm

1.66 stop = 360mm

2 stop = 420mm

 

The nice thing about this approach, is you can have a simple chart like this for all your lenses, measure between two points, glance at the charts, and your done. It makes no difference if it's a tele lens or normal lens, all that is worked out in advance. You can make the chart with more increments, but most f stop setting can't acheive much better than 1/3 stop increments. Hope this helps.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Johnathan.... I would challenge the method you are using. Here is a very simple approach. If the fl of the tele lens is 270mm, focus at infinity and mark the rail where the front standard is. Now focus at the closer object, calc. the additional extension required. (this is all that matters, lens nodal point, film plane, etc. is all taken in consideration when focussing at infinity) If you required an extra 270mm of extension, you add 2 stops. If you needed 135mm of addtional extension, 1 stop. You can use the same formula, just remember to use the fl as 2 full stops, the same you would do with any other lens, except your starting point is shorter with the tele vs. using a non tele lens. Try it with some polaroids.

Angus, the nodal point of a lens is where the rays cross, or form a sideways X in the lens. The nodal point is not a point in space. If you read the lens specification, it usualy will give you the nodal point.

 

To determine exp. compensation, use the advise above, focus at infinity, mark two points, if your using a rail camera, mark the standard distance on the rail, then focus on your subject, re measure. If your not using a rail, then measure the difference between the tops of the standards. Subtract the two readings. Take the difference X over the lens fl, X/fl. If the difference is 75mm with 150mm lens, this equals .5, mulitply by 2 stops, which equals 1 stop exposure compensation.

Scot, interesting report. How do you determine the poor image quality was a result of vibration, vs. wind, or other issues? Just curious.

OK, I tried all those, any other suggestions?

I tried Lens Repro and Fotocare, I will try to get contact information for the others you metnioned. It's not easy getting a list of rental houses...I'll check those out...

I tried all the major rental houses, could not find one.

Pete, I should have said, View Camera lenses.

Does anyone know where I can rent this lens? Or does anyone have one

I can ask some questions to? For example, how far does the image

circle travel before the light fall off equals 1/3 stop?

Roger, if you don't need full coverage on 4x5, maybe something between MF and 4x5, you should consider the digital lenses by Schneider. Unlike LF lenses these are optimised at f8 - 11, so 5.6 would perform very well. These lenses are the sharpest lenses made today. And amazingly enough the prices are not that expensive. Consider RW in the UK.

I second Ellis's comments, I went from Quantum to LPA pocket wizards with great success....

I have used both the B1 and Bogen standard 3 way heads for 4x5 and 8x10. There is no question the 3 way heads are more accurate and much easier to level the camera since your only dealing with one axis at a time. However, with the B1 you get two major advantages...the first is weight!!! IF you carry the tripod a lot, that extra 3 - 4 pounds makes a huge difference on your hands.... next you gain speed, once you get used to working the B1. If you loosen the set screw just enough, you can essential deal with one axis at a time...if you loosen it too much, then the axis get intermingled when adjusting. As with everything in photography, there is pros and cons to everything. BTW, there is also a few different ball heads to look at.... there is new one I read about on the luminous landscape site that appears to be pretty damn good and 1/2 the price....

Stefan, what do you mean by indirect rise. I assume this means tilting the rail to raise the front standard in relationship to the back standard, right? If so, then you need to tilt the rear standard and add the same tilt angle to the front tilt, right? Just making sure I understand you correctly...

From what I read about the orbix, it is a means to offer

simulated "lens axis" tilt and yaw free control. However, looking at

the design, it appears the "lens axis" tilt only exist if the front

standard uses NO rise. If rise is used, the orbix will improperly

tilt the lens and NOT provide true lens axis tilt. The more rise

used, the further off the lens axis tilt will be. One dealer

confirmed this, but he seemed a bit unsure. I have never used one

before, can any users shed some light on this?

Is anyone using the Rodenstock Digital 55 or 90 mm lenses? I was

told by someone the image circle values given, 125mm, are

overstated? Has anyone checked this? How is the quality using these

lenses with color film? Is there a noticeable improvement over

normal LF lenses, such as Grandagons?

Here is a cut from the B&H site, for the Arca 5x7 Metric compact...

 

MINIMUM EXTENSION

 

3.2" (80mm) with standard bellows and flat lensboard,

 

2.6" (65mm) with standard bellows and 13mm recessed lensboard,

 

2.2" (55mm) with wide-angle bellows and 13mm recessed lensboard

 

So it appears the 13mm reccess board is mandatory? From what I can tell, I can fit the two lenses on the 13mm recessed board, assuming it only takes up 10mm on each side. At 55mm, I wonder if tilt can be used, without the rear of the lens whacking the gg?

Does anyone know where the PDF file is that details all the Arca Swiss products? I remember someone posting it awhile ago. What is the phone number of Arca USA?

Ellis, that is great news... Thank you. From the looks of the 5x7 F compact metric picture, it appears the front standard really packed in nice and tight, almost as if the back of the lens would smack the gg! With the 55 mm lenses this close to the gg, I only plan to use rise and maybe 2 degrees of front tilt. Do you think this can be acheived with the flat lens boards? Or would the 13mm reccess boards be required? Also, when on a tripod, can the rail be manipulated to move behind the camera a bit, so as to prevent the rail from getting into the image?

The Canham uses the smaller Toyo field boards, 110 mm square, otherwise it would be perfect. As for which lens...I should have explained, I am trying to mount two 55 mm Rodenstock Apo Sironar digitals to a large lens board (min 158 mm square) to shoot stereo, on 1/2 5x7 sheet. Of course no 55's will cover 5x7. I think this application fell between the cracks a bit... If anyone knows if the Arca will get this close, please advise, thank you...

From the Bromwell site,

 

1. Lens board is 92 x 104 (way smaller than 158 mm square)

2. Min. bellows extension 70mm.

 

Is it possible I was looking at the wrong camera? From this site, it appears they only have one 5x7?

 

Bill

I am trying to find a reasonalby light and compatct 5x7 for field

use. It does NOT have to be a clamshell design. My requirements are:

 

1. Large lens board, Toyo size (158mm square, or larger)

2. Can focus down to 55mm lens without recessed board.

 

So far, only the Arca Swiss 5x7 F Metric meets this

criteria...and even then, I am assuming it will focus a 55 mm lens if

used with a bag bellows. (but I never read this anywhere)

 

Any suggestions? Thank you all in advance.

I am trying to figure out the difference between the above two

lenses. From the Rodenstock site....

 

The Rodenstock Apo-Sironar digital HR was developed for special

applications with extremely high resolution CCD chip cameras and CCD

line scanner cameras with pixel sizes of < 10 ìm such as can only be

realized with smaller digital camera formats.

 

So does this mean the HR will produce sharper images using

film vs. the non HR digital lenses? How much sharper are these

lenses on film vs. modern non digital LF lenses?

No, it is not part of any quick release system. YOu need to mount a quick release system to it...a Arca is not a bad idea as it conforms well to the bottom plate of the VX.

I have a 1024 x 728 plasma, 37" 4:3 aspect ratio, the resolution is fair at best... just remember, its resolution vs. viewing distance. My plasma looks great if you stand back 4 screen diaganols! However LCD's have just been announced with 4x the resolution of current models...these are so sharp they can be used in the darkroom!