Macro with RB67 and 50mm Sekor C

[Donald Qualls]

My new-to-me 50mm f/4.5 came yesterday (lots of wear on the black finish, but the glass is very clean and shutter seems accurate). "Guaranteed delivery by Wed. 12/23" said the eBay listing, then "Arriving 12/21" on the tracking, then the UPS truck backed in on Saturday the 19th. Can't fault that!

I noticed when I mounted it to check function that I can focus really close -- the bellows draw that would let me focus to 2 meters or so with my 250 mm gets me down to around 10 cm with the 50mm. I look forward to using this that way, even though I mainly wanted it for wide panoramics with 35mm film.

The camera body (RB67 Pro S, if that makes a difference) has an exposure compensation (bellows factor) scale by the right focus knob, but reading it is a little cryptic. It seems to be marked in mm at the top of the scale, and then there are sloping, slightly curved lines for different focal lengths (seemingly covering the entire range offered by Mamiya, at least when this camera was made -- no 30 mm for the fisheye, but I think that was a later lens offering, from the Pro SD era). I've never paid attention to this before, because this is an SLR and I haven't done close focus images with it (yet).

The millimeter scale is easy to read, so I can manually calculate the corrected f stop -- 50mm plus 8 mm bellow draw would give 50/32 = 58/X, X = 32 x 1.16 = ~37, so effectively 1/3 stop extra time needed. The curves seem to be mainly about scale focusing -- but the compensation markings don't seem to want 1/2 stop extra time, even for 50mm, until I have 11 mm of draw -- 50/22 = 61/X, X = 22x1.22 = ~27 -- but if I focus near minimum distance (= largest image on the film, should be near 1:1 with 45mm of bellows) I'll have almost doubled the effective focal length -- and the compensation scale clearly only reads +1 stop, while it seems like it should be approximately +2 stops, as if I had a 2x tele-converter mounted (50/22 = 95/X, X = 22x1.9 = ~42).

Is the scale wrong, am I reading it the wrong way, or do I completely misunderstand bellows draw compensation? My previous experience with macro has been either with diopters (no compensation needed) or with cameras that meter through the lens, thereby automatically compensating for the extension rings.

 

[mitch brown]

Good morning
I havent used mine for macro but i do remember that the manual has the info you are looking for .you can find it very easy online and it is the same for all the models
if you cant find it let me know and i will send you a copy. try this link Mamiya RB67 PRO-S instruction manual, user manual, free PDF manual, free manuals camera guide (butkus.org)
Mitch

 

[Donald Qualls]

Good morning
I havent used mine for macro but i do remember that the manual has the info you are looking for .you can find it very easy online and it is the same for all the models
if you cant find it let me know and i will send you a copy. try this link Mamiya RB67 PRO-S instruction manual, user manual, free PDF manual, free manuals camera guide (butkus.org)
Mitch

The scale on the camera is clear enough in terms of what Mamiya intended, I think -- it's got shaded bars for + 1/2 and + 1 for each focal length lens, and they're close to the same length (the 250mm I have, at least, seems to be a true tele; it's nothing like 250 mm from aperture to film plane -- not much if any over half that; the shortest extension to need compensation is the 127 mm, which seems odd). That may be due to retrofocus for the 65mm and 50mm lenses, and telefocus for the 127 and longer -- but it doesn't cover why their compemnsation is half what I expect it to be.

 

[ic-racer]

Retrofocus lens; use the scale on the camera.

 

[Donald Qualls]

Retrofocus lens; use the scale on the camera.

Can you elaborate? The focusing scale shows different curves for each focal length -- the one for 50mm is so steep as to be difficult to read a distance, while the one for 360 mm is very long, and the slopes of the curves are in order and approximately proportional as focal length increases -- but the compensation bars are all over the place, and shortest draw for compensation to longest isn't much of a difference. How does retrofocus or telefocus change the draw compensation?

 

[Alan Edward Klein]

Maybe these will help.

 

[Alan Edward Klein]

Another sheet. Note the comments about 50mm.

 

[etn]

The exposure compensation table on the camera is a brilliant idea! Hasselblad forces you to carry a close-up calculator. (I agree, it's a small problem...)

 

[138S]

The exposure compensation table on the camera is a brilliant idea! Hasselblad forces you to carry a close-up calculator. (I agree, it's a small problem...)

Or you may use a finder with TTL meter... both in the hassie or in the RB67

To go around the penta-prism of the RB67 weights a lot... The RZ has a penta-mirror that's lightweight, if IIRC the pentamirror cannot be mounted in the RB, sadly.

 

[mshchem]

I always use a tape measure and a Kodak master photoguide. If you are at 1:1 add two stops. The little pocket photoguides that Kodak sold by the millions 50 years ago are indispensable. The little dials let you dial in extension and focal length. EZ

 

[narsuitus]

I have never needed to use my 50mm wide-angle for macro work. The 90mm normal lens and 140mm macro lens are all I have ever needed. With these two lenses, I can easily obtain a 1:1 macro shot.

At first, I tried using the scale on the side of the RB67 camera body for bellows factor exposure compensation but found it useless for my macro work because my scale does not include the 140mm macro lens and it does not compensate for the extension tubes I use in addition to the bellows.

With the 90mm lens, I use the full 40mm bellows extension plus the 45mm extension tube to fill the 6x7cm frame with a 7cm subject for a 1:1 ratio.

With the 140mm lens, I use 6mm of bellows extension plus the 45mm extension tube plus the 82mm extension tube to fill the 6x7cm frame with a 7cm subject for a 1:1 ratio.

Either way, I know that the extension for a 1:1 macro shot requires a 2-stop exposure compensation. No need for the scale.


RB67 macro by Narsuitus, on Flickr


RB67 1:1 Macro by Narsuitus, on Flickr

 

[MattKing]

How does retrofocus or telefocus change the draw compensation?

By moving the nodal point in relation to the position of the lens mount, and therefore in relation to the position that that exposure compensation scale works with.
For clarity, it doesn't change the compensation, it changes how that indicator shows the compensation.
With a retrofocus or telephoto lens you can't use tape measures to (easily) calculate exposure compensation, unless you can figure out where that nodal point actually is, because that is where you need to measure from.
It is better to use magnification to do the calculation, and even better to use the scale.
Speaking generally though, while the 50mm lens permits very close work, it isn't a stellar performer if you need flat field close work.

 

[Alan Edward Klein]

I have never needed to use my 50mm wide-angle for macro work. The 90mm normal lens and 140mm macro lens are all I have ever needed. With these two lenses, I can easily obtain a 1:1 macro shot.

At first, I tried using the scale on the side of the RB67 camera body for bellows factor exposure compensation but found it useless for my macro work because my scale does not include the 140mm macro lens and it does not compensate for the extension tubes I use in addition to the bellows.

With the 90mm lens, I use the full 40mm bellows extension plus the 45mm extension tube to fill the 6x7cm frame with a 7cm subject for a 1:1 ratio.

With the 140mm lens, I use 6mm of bellows extension plus the 45mm extension tube plus the 82mm extension tube to fill the 6x7cm frame with a 7cm subject for a 1:1 ratio.

Either way, I know that the extension for a 1:1 macro shot requires a 2-stop exposure compensation. No need for the scale.

Here's the scale from the manual. It doesn't show the 50mm. But it has the magnifications for both macro extension tubes and the additional stops for the bellow's extensions.

 

[Donald Qualls]

By moving the nodal point in relation to the position of the lens mount, and therefore in relation to the position that that exposure compensation scale works with.
For clarity, it doesn't change the compensation, it changes how that indicator shows the compensation.
With a retrofocus or telephoto lens you can't use tape measures to (easily) calculate exposure compensation, unless you can figure out where that nodal point actually is, because that is where you need to measure from.
It is better to use magnification to do the calculation, and even better to use the scale.
Speaking generally though, while the 50mm lens permits very close work, it isn't a stellar performer if you need flat field close work.

Okay, right. The rear node for the 50mm must be well back inside the camera body to begin with, else it'd be a 90mm, give or take. But the compensation is derived from the actual distance from film to aperture, which is why it's almost the same for the 50, 65, and 90 lenses -- and then again for the tele 180, 250, and 360. The 90 and 127 don't have weird optical stuff going on, so their compensation is "normal"...

Yeah, the 50 is way out of its design parameters at four inches lens to subject -- it's optically designed to focus down to three feet or so. I think I've got a set of 77mm diopters, though; those should let me get close without moving the lens so far from the film, which ought to help some with the field curvature problems in macro work.

 

[narsuitus]

Here's the scale from the manual. It doesn't show the 50mm. But it has the magnifications for both macro extension tubes and the additional stops for the bellow's extensions.

Thanks for the scale from the manual. Regretfully, not only does it not have the 50mm lens but it also does not have the 140mm macro lens. However, the 90mm information looks accurate.

 

[narsuitus]

I think I've got a set of 77mm diopters, though; those should let me get close without moving the lens so far from the film, which ought to help some with the field curvature problems in macro work.

I have a set of +1, +2, +4, and +10 77mm diopters that I use with my RB67 bellows and extension tubes so I can obtain magnifications greater than what I can obtain with bellows alone, extension tubes alone, or bellows and extension tubes combined.

What type of macro subjects will you be shooting and how much magnification will you need?

 

[Alan Edward Klein]

Thanks for the scale from the manual. Regretfully, not only does it not have the 50mm lens but it also does not have the 140mm macro lens. However, the 90mm information looks accurate.

Maybe the 50mm came out later. It could be in the RZ67 manual or a later RB manual. Don't know?

 

[Alan Edward Klein]

I have a set of +1, +2, +4, and +10 77mm diopters that I use with my RB67 bellows and extension tubes so I can obtain magnifications greater than what I can obtain with bellows alone, extension tubes alone, or bellows and extension tubes combined.

What type of macro subjects will you be shooting and how much magnification will you need?

What do you shoot that you need all those?

 

[narsuitus]

What do you shoot that you need all those?

At one time, I shot a lot of pathological lesions that could be as small as a few millimeters in size.

Now that I am retired, I shoot art work, postage stamps, coins, diamonds, and jewelry.

However, when I need to shoot very small subjects, I tend to use a small format camera instead of a medium format camera.

 

[Maris]

Retrofocus lens; use the scale on the camera.

Yes! I've used a Mamiya RB67 with the 50mm lens for a long time both for wides and close-ups and the compensation scale on the camera is good. The 50mm is a strong retrofocus design so the entrance and exit pupils are different sizes so the effective f-stop (pupillary magnification effect) is not what simple geometry would imply.
Don't forget to set the floating element control ring to the right distance or near to it. The floating element does not make a lot of difference at infinity but in close-ups the corner image quality is definitely improved by the right setting.

 

[Donald Qualls]

What type of macro subjects will you be shooting and how much magnification will you need?

In the past, I've shot flowers for the most part (get this: with a Pony 135 and a diopter, or with a Kodak Reflex II and my dad's glasses as a diopter). I'm sure I'll find other things if I have the setup on a camera I'm using regularly.

Don't forget to set the floating element control ring to the right distance or near to it. The floating element does not make a lot of difference at infinity but in close-ups the corner image quality is definitely improved by the right setting.

Oh, that's the ring that I thought was for reading DOF? I wondered why it moved. Yes, set to match actual working distance. Won't be a change I can see in the viewfinder, but it'll show on a large print.

 

[narsuitus]

In the past, I've shot flowers for the most part (get this: with a Pony 135 and a diopter, or with a Kodak Reflex II and my dad's glasses as a diopter).

With the RB67 bellows fully extended to 45mm, the 90mm normal lens will fill the 6x7cm frame with a 13cm object. This is approximately a 1:2 ratio (about half life size). Based on my calculations, a 1:2 ratio requires a 1 1/3 stop bellows extension correction. Adding a diopter to the lens sounds like a good idea. You will get additional magnification and will not need exposure compensation.

 

[MattKing]

This might be of assistance: https://www.cameramanuals.org/mamiya_pdf/mamiya_rb_lenses.pdf
If you find it useful, I'd suggest sending Mr. Butkus his requested donation.

 

[ic-racer]

Can you elaborate? The focusing scale shows different curves for each focal length -- the one for 50mm is so steep as to be difficult to read a distance, while the one for 360 mm is very long, and the slopes of the curves are in order and approximately proportional as focal length increases -- but the compensation bars are all over the place, and shortest draw for compensation to longest isn't much of a difference. How does retrofocus or telefocus change the draw compensation?

Since it is retrofocus design, using 50mm for the focal length in the "bellows equation for simple lenses" give the wrong answer. The camera designers already figured this out for you and printed it on the scale on the camera; they did not make a mistake.

 

[MattKing]

The metered chimney finder is also a good solution for close-up work with the RB67. If you get the latest PDN version, it uses Silicon Blue cell(s).
It is quite light, but definitely bulky in the bag.