Are any of you using diopters for the Mamiya RB67 waist lever viewfinder? Do you have spare ones?

Certain Exposures · Sep 24, 2023

Have any of you gone through several of the RB67 diopters? Did it make a dramatic difference in your ability to achieve focus?

I have been struggling to achieve sharp focus even when I increase the depth of field because the waist-level finder on my RB67 doesn't have an obvious "sharp" point. I have to hunt for too long to try and find a "range of sharpness" instead.

I can nail focus wide open on 35mm manual focus lenses and 4x5 without too much of a challenge.

Sellers are listing RB67 diopters at $50 a pop because they are (allegedly) rare items. I have not confirmed if the RB/RZ diopters are interchangeable yet. They are often listed as if they are. A few listings suggest that RB67 diopters and M645 diopters are also interchangeable.

I took a look at some information about diopters online. Generally, articles focus on the positive (+) diopters. From what I can tell, those should magnify the image on the ground glass. The Pro-S system manual shows that Mamiya only made a +1 RB67 diopter and a range from -1 to -3. I wonder why they provided more options in the negative range.

Here's an image of the best critical sharpness I've achieved with the RB67 at a lower F stop.

P.s. if you've followed any of my other threads, this problem exists even when I use a 120 film back. I mentioned how I use 120 film in a 220 back in other threads.

(http://imgur.com/a/7Hd3xLs)

john_s · Sep 24, 2023

My understanding is that the diopters are for eyesight correction, which is what I use them for on several cameras. I am short sighted so use a negative diopter. Although they might well alter the magnification slightly, that is not their function.
Do your eyes focus unaided at distant objects? If so, according to various instructions I've read, you don't need a diopter.
For my 35mm rangefinder, I also have a magnifier that screws into the viewfinder, and that is a different construction.

awty · Sep 24, 2023

I wonder if the focus screen on the RZ is better. It is defiantly better than my Mamiyaflex which I have the same issue with, but I have no issue with the RZ.
I have never used a RB

L Gebhardt · Sep 24, 2023

Are you using the waist level finder pop-up magnifier? With it can you focus on the fine ridges of the focus screen? How about the dust and lint that invariably collects on the surface? If so I don't think you need a diopter. Note that the magnifier on mine does not have any diopter markings, but it obviously is a magnifying lens.

Confirm the focus screen is seated properly, and do a test shot wide open and close of something running at an angle like a fence, piece of newspaper or a book on a table. Focus and see if the point of focus on the screen ends up being the sharpest spot on the film. If not you have an issue with the screen placement or the mirror.

I'm using an RZ67, but all the waist level finders I've used are basically the same.

Certain Exposures · Sep 24, 2023

john_s said:
My understanding is that the diopters are for eyesight correction, which is what I use them for on several cameras. I am short sighted so use a negative diopter. Although they might well alter the magnification slightly, that is not their function.
Do your eyes focus unaided at distant objects? If so, according to various instructions I've read, you don't need a diopter.
For my 35mm rangefinder, I also have a magnifier that screws into the viewfinder, and that is a different construction.

Thanks, I wear contacts so I'm unsure if myopia or hyperopia would still be a factor.

My diopter doesn't have a number on it. That means it could be fake or it could be a zero judging by pictures on eBay. The -1.5 diopter has a clear -1.5 printed on it. I also just learned that -1.5 was the "standard" diopter based on the manual. So, maybe this is why I've had such a hard time.

Unfortunately, there aren't many -1.5s for sale.

awty said:
I wonder if the focus screen on the RZ is better. It is defiantly better than my Mamiyaflex which I have the same issue with, but I have no issue with the RZ.
I have never used a RB

Thanks, I've been told it's slightly better.

L Gebhardt said:
Are you using the waist level finder pop-up magnifier? With it can you focus on the fine ridges of the focus screen? How about the dust and lint that invariably collects on the surface? If so I don't think you need a diopter. Note that the magnifier on mine does not have any diopter markings, but it obviously is a magnifying lens.

Confirm the focus screen is seated properly, and do a test shot wide open and close of something running at an angle like a fence, piece of newspaper or a book on a table. Focus and see if the point of focus on the screen ends up being the sharpest spot on the film. If not you have an issue with the screen placement or the mirror.

I'm using an RZ67, but all the waist level finders I've used are basically the same.

Thanks, yes, I use the pop up magnifier. The pop up magnifier is what uses a diopter.

I cannot answer your second question at the moment because I haven't really tried that. I'll look into this and update my post later.

I also haven't checked the placement of the screen or mirror yet. I have done several DoF tests. The flower DoF test in my initial post is a good indication that the area I intend to have in focus based on what I see in the screen is the sharpest area on the film. I.e., I did intend to make that flower the point of focus. I'll try out a fence test.

I'm not sure what the standard diopter is on a RZ67. If it's the same as an RB67 then you're not using the standard one. I suppose there are several reasons that could matter more to some than others.

Nopo · Sep 24, 2023

My advice, FWIW, is to do the system focus test as suggested by

L Gebhardt said:
Confirm the focus screen is seated properly, and do a test shot wide open and close of something running at an angle like a fence, piece of newspaper or a book on a table. Focus and see if the point of focus on the screen ends up being the sharpest spot on the film. If not you have an issue with the screen placement or the mirror.

before buying diopter systems.

The flower photo doesn't tell me anything about possible problems with your mamiya system due to lack of sharpness, I think you already returned a 50mm lens for possible sharpness problems, when possibly you have them with other lenses as well.

Certain Exposures · Sep 24, 2023

Nopo said:
My advice, FWIW, is to do the system focus test as suggested by

before buying diopter systems.

The flower photo doesn't tell me anything about possible problems with your mamiya system due to lack of sharpness, I think you already returned a 50mm lens for possible sharpness problems, when possibly you have them with other lenses as well.

Thanks, can you rephrase or clarify your last sentence? Why do you think the flower test does not tell you anything? Does the flower look like it is in focus on your monitor?

I'll make time for the test in a week or two.

L Gebhardt · Sep 24, 2023

Certain Exposures said:
I have done several DoF tests. The flower DoF test in my initial post is a good indication that the area I intend to have in focus based on what I see in the screen is the sharpest area on the film. I.e., I did intend to make that flower the point of focus. I'll try out a fence test.

I'm not sure what the standard diopter is on a RZ67. If it's the same as an RB67 then you're not using the standard one. I suppose there are several reasons that could matter more to some than others.

While you're sorting this out I would also use a tripod and the mirror lockup function with static subjects. I can not hold the RZ stable for enough for shots like your flower, plus the wind can move plants more than you would expect.

Certain Exposures · Sep 24, 2023

L Gebhardt said:
While you're sorting this out I would also use a tripod and the mirror lockup function with static subjects. I can not hold the RZ stable for enough for shots like your flower, plus the wind can move plants more than you would expect.

Thanks, I did not use mirror lock-up for the flower shot above because that lens had a broken mirror lock-up socket (I returned it). However, I did have the camera on a tripod.

Since then, I've used a tripod and mirror lock-up for all photographs. Unfortunately, I've still noticed this problem. I will use mirror lock-up for my test.

Nopo · Sep 24, 2023

Certain Exposures said:
Thanks, can you rephrase or clarify your last sentence? Why do you think the flower test does not tell you anything? Does the flower look like it is in focus on your monitor?

I'll make time for the test in a week or two.

I think, from what I see on my monitor, that the flower has a "possible" lack of sharpness, this may be due to a real lack of sharpness in your mamiya or to a focusing problem of the screen or to my monitor.
That's why I advised you to perform the test that L Gebhardt wrote.
I hope I have clarified your doubt about my statement, if not please let me know.

Carlos

ags2mikon · Sep 24, 2023

I need positive correction for my old tired eyes and this is what I did. I removed the lens placed the camera on a tripod and opened the wl finder pointed the camera at a light source and then got out my + diopter series 7 set out and used one supplementary lens at a time until the grain of the screen was real sharp wearing my glasses and ordered the closest correction I could find. It's perfect now for me. My wife can't see any thing with it now. I have also bought "reader" glasses from Walgreens for some of my cameras and I keep them in the camera case just for shooting with them.

mshchem · Sep 25, 2023

250mm, is a long lens for 6x7. Up close depth of field is very narrow. If you want to see if you are in focus I would try shooting a static subject, indoors on a tripod and use a flash. Try different apertures. Make sure you have a lot of detail in your subject.

One easy way to check what (positive) diopter you might need is go to a store that sells reading spectacles. These are 5 bucks at Wal-Mart. Take the camera in with you, don't use the magnifier in the finder. A routine eye exam will tell you how much diopter you need for reading.

Certain Exposures · Sep 25, 2023

By the way, do any of you happen to have a link to a helpful thread on disassembling the focusing screen, cleaning it, and reassembling it? I didn't see a video online or a guide in this forum. I did skim quickly. My screen is dim. It's not dim enough to explain this problem though.

L Gebhardt said:
Confirm the focus screen is seated properly, and do a test shot wide open and close of something running at an angle like a fence, piece of newspaper or a book on a table. Focus and see if the point of focus on the screen ends up being the sharpest spot on the film. If not you have an issue with the screen placement or the mirror.

I'm going to try and do this test tonight because I've got a shoot coming up. No promises though!

mshchem · Sep 26, 2023

Certain Exposures said:
By the way, do any of you happen to have a link to a helpful thread on disassembling the focusing screen, cleaning it, and reassembling it? I didn't see a video online or a guide in this forum. I did skim quickly. My screen is dim. It's not dim enough to explain this problem though.

I'm going to try and do this test tonight because I've got a shoot coming up. No promises though!

Be careful. I would use a soft camel hair brush. No solvent. Most of the screens I've come across are extremely delicate. The shiny glass side can be gently cleaned with a slightly damp lens tissue, the side towards the lens shouldn't be touched, just very delicately brushed. Could be the mirror needs cleaning, but then again these are very delicate.

Certain Exposures · Sep 26, 2023

mshchem said:
Be careful. I would use a soft camel hair brush. No solvent. Most of the screens I've come across are extremely delicate. The shiny glass side can be gently cleaned with a slightly damp lens tissue, the side towards the lens shouldn't be touched, just very delicately brushed. Could be the mirror needs cleaning, but then again these are very delicate.

Thanks. When you say “towards the lens,” you mean the bottom of the screen, right?

I overestimated how much time I had yesterday. I should be back to update this thread with scans from the focus test this weekend.

Arthurwg · Sep 26, 2023

Try a split image Brightscreen MPD, available from Rick Oleson.

mshchem · Sep 26, 2023

Arthurwg said:
Try a split image Brightscreen MPD, available from Rick Oleson.

+1

Certain Exposures · Sep 26, 2023

Arthurwg said:
split image Brightscreen MPD, available from Rick Oleson.

mshchem said:
+1

It's interesting that his site says the MP (micro prism) is better for portraits than the MPD (split screen).

I mainly need better focus for portraits.

Have any of you tried both?

reddesert · Sep 26, 2023

The question asked above, can you see the texture of the focusing screen when looking through the magnifier, is important. If you can focus your eye on that texture, then you shouldn't need to change diopters, and issues with obtaining focus may have to do with technique or some camera/lens issue.

Sometimes people new to medium or large format have difficulty focusing on the matte screen without a split image focusing aid, but you have experience with large format so that shouldn't be an issue.

By default, camera eyepieces are usually set up to produce a virtual image at a distance of about 0.5-1 meter. WLF magnifiers are similar. If you can focus on objects at that distance, you can typically use the default eyepiece. Different values of numerical diopters may allow glasses-users to focus without their glasses, which doesn't apply to you since you have contacts.

itsdoable · Sep 26, 2023

I have not been able to open your image link, I get a "waiting for ssbsync.smartadserver.com" error. Same if I go to Imgur.

Thus I can't tell if you are front focused, back focused, or just blurry - or if you have a problem with your focusing, or a problem with the camera.

Diopters are used for relating the distance the optical system places the virtual image. A 0 diopter means that the image appears sharp when your eyes are focused at infinity. -1 means that the image appears as if it's placed at 1 meter. Thus many cameras use either a 0 or 1 as the base optical correction. A -1.5 diopter means the image appears at 75cm distance.

If you can see the detail on the focus screen clearly (ie: etched lines or focus aid boundaries) then you probably have the correct eyepiece.

You should probably do a proper focus test to see where the plan of focus falls with respect to the focus screen, with a lens wide open.

Certain Exposures · Sep 26, 2023

reddesert said:
The question asked above, can you see the texture of the focusing screen when looking through the magnifier, is important. If you can focus your eye on that texture, then you shouldn't need to change diopters, and issues with obtaining focus may have to do with technique or some camera/lens issue.

Sometimes people new to medium or large format have difficulty focusing on the matte screen without a split image focusing aid, but you have experience with large format so that shouldn't be an issue.

By default, camera eyepieces are usually set up to produce a virtual image at a distance of about 0.5-1 meter. WLF magnifiers are similar. If you can focus on objects at that distance, you can typically use the default eyepiece. Different values of numerical diopters may allow glasses-users to focus without their glasses, which doesn't apply to you since you have contacts.

Thanks,

I can see dust and hairs that look fairly sharp when I point the lens at a bright light source.

I can also see extremely thin, faint rings extending out from the center micro prism (not split prism).

Focusing becomes a chore as soon as a move away from a brilliant light source like a light bulb. E.g., if I try focussing on the edge of a cardboard box in the corner of an average lit room. At night, it's still too tough to focus on a model lit by fairly bright street lamps.

itsdoable said:
I have not been able to open your image link, I get a "waiting for ssbsync.smartadserver.com" error. Same if I go to Imgur.

Thus I can't tell if you are front focused, back focused, or just blurry - or if you have a problem with your focusing, or a problem with the camera.

Diopters are used for relating the distance the optical system places the virtual image. A 0 diopter means that the image appears sharp when your eyes are focused at infinity. -1 means that the image appears as if it's placed at 1 meter. Thus many cameras use either a 0 or 1 as the base optical correction. A -1.5 diopter means the image appears at 75cm distance.

If you can see the detail on the focus screen clearly (ie: etched lines or focus aid boundaries) then you probably have the correct eyepiece.

You should probably do a proper focus test to see where the plan of focus falls with respect to the focus screen, with a lens wide open.

Try turning off your VPN if you have one and use this link without the quotations: " (http://imgur.com/4nlYZjY) " . It's safe. I can add an attachment later.

Your description about 0, -1, and -1.5 confused me a little. What does it mean for my eye to be "focused at infinity" when I look into a waist level viewfinder? What does it mean for "the [image to appear] at 75cm distance" when I look into a waist level viewfinder?

For example, let's say I have a subject (a rabbit) 10 feet away from me. I pull out my camera, look through the waist level viewfinder, pull up the diopter, and look through the diopter as I begin moving the bellows so the lens is hunting for focus. At what point would my eye be "focused at infinity?" At what point would the image be "focused at 75cm?"

I will do the focus test. So far it has been easier to type up for a few minutes between working than pull everything out for a serious test!

. . .

Do any of you happen to know what the diopter on a Yashica 124g is? I'm looking around because I always nailed focus when I owned that camera - even in low light. I always used the diopter on it.

mshchem · Sep 26, 2023

Certain Exposures said:
It's interesting that his site says the MP (micro prism) is better for portraits than the MPD (split screen).

I mainly need better focus for portraits.

Have any of you tried both?

I have used matte Acute-matte screens with Hasselblad bodies. Typically split image screens work best with fast normal lenses. Especially with a really quite long lens like a 250mm you want a smooth screen. All the bright screens rely on something like a Fresnel lens to boost the brightness, the Acute-matte was a Minolta development, much more complicated than a Fresnel, they developed the screens for the Hasselblad cameras. I've not tried others for medium format.

mshchem · Sep 26, 2023

Certain Exposures said:
Thanks,

I can see dust and hairs that look fairly sharp when I point the lens at a bright light source.

I can also see extremely thin, faint rings extending out from the center micro prism (not split prism).

Focusing becomes a chore as soon as a move away from a brilliant light source like a light bulb. E.g., if I try focussing on the edge of a cardboard box in the corner of an average lit room. At night, it's still too tough to focus on a model lit by fairly bright street lamps.

Try turning off your VPN if you have one and use this link without the quotations: " (http://imgur.com/4nlYZjY) " . It's safe. I can add an attachment later.

Your description about 0, -1, and -1.5 confused me a little. What does it mean for my eye to be "focused at infinity" when I look into a waist level viewfinder? What does it mean for "the [image to appear] at 75cm distance" when I look into a waist level viewfinder?

For example, let's say I have a subject (a rabbit) 10 feet away from me. I pull out my camera, look through the waist level viewfinder, pull up the diopter, and look through the diopter as I begin moving the bellows so the lens is hunting for focus. At what point would my eye be "focused at infinity?" At what point would the image be "focused at 75cm?"

I will do the focus test. So far it has been easier to type up for a few minutes between working than pull everything out for a serious test!

. . .

Do any of you happen to know what the diopter on a Yashica 124g is? I'm looking around because I always nailed focus when I owned that camera - even in low light. I always used the diopter on it.

Aha, you need to work with a spotlight or buy one of the new Nikon Zf cameras that focus in the dark, moonlight.

mshchem · Sep 26, 2023

Most newer prism finders, especially for 35mm and DSLRs have adjustable diopters so you don't have to fool with changing them around. If you focus a Nikon F5 or F100 for an example, at a object at a distance, setting the lens at infinity, you next set the diopter to obtain sharp focus, easily done my adjusting until the viewfinder image is sharp and the elements of the screen are sharp such as the cross lines and the like.

MattKing · Sep 26, 2023

Certain Exposures said:
Your description about 0, -1, and -1.5 confused me a little. What does it mean for my eye to be "focused at infinity" when I look into a waist level viewfinder? What does it mean for "the [image to appear] at 75cm distance" when I look into a waist level viewfinder?

For example, let's say I have a subject (a rabbit) 10 feet away from me. I pull out my camera, look through the waist level viewfinder, pull up the diopter, and look through the diopter as I begin moving the bellows so the lens is hunting for focus. At what point would my eye be "focused at infinity?" At what point would the image be "focused at 75cm?"

The system isn't designed to cause you to focus on the magnifier itself, or on the focusing screen itself.
It is designed so that when you use the magnifier to view the image on the focusing screen, your eye should be focused in the same way that your eye is focused when you look at something a long way away - effectively infinity.
To make that happen, the standard magnifier will have a built in magnification factor - its "diopter".
If your eyesight is such that you normally need correction to see objects in the distance clearly, you need a magnifier with a different diopter than the diopter needed for those with standard distance eyesight.
The additional confusing factor is that the accessory correction lenses may have their power (diopter) shown in two ways - either the actual diopter measurement, or the offset from the standard diopter measurement that the accessory lens incorporates. And sometimes it can be difficult to know which approach was used by the manufacturer.

Are any of you using diopters for the Mamiya RB67 waist lever viewfinder? Do you have spare ones?

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