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Lorriman
Tinkerer
Username: Lorriman
Post Number: 9
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, October 13, 2009 - 09:00 am: | 
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I want an accurate view of the look and degree of bokeh. I haven't been able to find this even with older cameras. For exmaple I got a cheap Spotmatic for the purpose but it seems almost as innacurate a view of the image as a Canon 450D (except in live view, of course).
Maybe the Spotmatic I'm using has been messed about with because the viewfinder is really surprisingly bright, and it turned out to be 3cm out of alignment. If anyone has the oppotunity to compare the image formed at the film plane with that of a their spotmatic viewfinder I would be grateful for the report.
It would appear that opaque sellotape, which is how I test viewfinder alignment, gives me the most accurate view. So I'm thinking of replacing the focusing screen with that. So now I'm on to the selection process.
Could you advise me as to which of the cheaper cameras you think I might be able to easily fiddle with in this respect. I've previously been advised here that both the Canon AL-1 and Minolta XG-M are much too hard. Perhaps the Spotmatic is more approachable, or maybe an older Canon.
I have considered a Canon F1 for it's focus screen accessibility, but they are a bit on the pricey side, particularly if I screw it up. Which is why I'd rather go for something like the spotmatic as not only do my lenses fit right on but I can get them for about £12.
Any words of wisdom? Obviously you may disagree with my mission but besides that... |
Glenn
Tinkerer
Username: Glenn
Post Number: 685
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, October 13, 2009 - 01:02 pm: |
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You obviously have not thought the sellotape bodge through to the proper logical conclusion - a plain ground glass/plastic screen. Get yourself a Canon F-1 or T90 and fit the correct plain ground screen. We were using these in the field years ago - worked perfectly, 100% accurate viewfinders and if the lens being used gives good/pleasant bokeh, you will see it! |
Lorriman
Tinkerer
Username: Lorriman
Post Number: 10
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 14, 2009 - 02:54 pm: |
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hi glenn,
Assuming I would rather play with my Spotmatic or something less expensive than an F-1 any words of advice? Is a spotmatic as tricky as aCanon AL-1 or Minolta XG-M?
There are other reason's I don't want to go the F-1 route apart from price, although I mayh be forced to eventually. In the meantime I have a useless spotmatic that perhaps I could adjust and turn in to my dream camera. |
Glenn
Tinkerer
Username: Glenn
Post Number: 688
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 14, 2009 - 04:00 pm: |
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The Spotmatic is a camera I have never worked on - but as you have already got one why not strip out the prism and screen and have a look? I understand what you are trying to achieve, but my feeling is that you should start with a purely mechanical camera. Any camera with a load of circuitry over and around the prism will be difficult to to work on - the circuits are very easily damaged. I am only talking about reaching the screen in the above comments, not making structural modifications with all the fiddling that entails. No matter what camera you choose to work on, placement of the substitute screen in the correct position is going to be very problematic.
I suppose you could adhere the tape to a screen sized piece of thin rigid clear plastic, placing the face of the tape on the original screen locators should keep the screen/film plane distances equal. However you locate the tape, you must ensure that it is completely flat when located in the camera - any lack of tension that allows the tape to become convex/concave will completely bugger the focus in the film plane. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 993
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 14, 2009 - 08:05 pm: |
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If I remember right, Spotmatics are not the easiest cameras to swap screens in.
I don't understand your description of your problems with the screen, though, particularly the "3 cm out of alignment". What sort of alignment? Focus? If so, 3 cm out at what distance? Infinity, or 1M, or 3 cm, or what? Or do you mean it's off laterally by 3 cm? in which case, the same question applies. It can't be simply 3 cm out laterally, the entire screen is only 2.4 x 3.6 cm, you'd be left with no screen at all. In either case, I don't know what replacing the screen with cello tape would improve. If the focus is out, that's adjustable... if the screen is off laterally, that may be a function of the construction of the camera that simply changing the screen will not change.
OM-1 through -4 cameras have easily interchangeable screens, but the design would not facilitate making a screen out of cello tape (though I HAVE made one out of .040" flat plastic, using sandpaper to rough up one side for focusing. That worked, but of course it was abysmally dim without any Fresnel rings in it). The Nikon F has a 100% accurate viewfinder and a drop-out interchangeable screen, and you can often pick up an F fairly cheap. This is one that you could get a spare screen, remove the glass from the frame and do whatever you like with it.
But I still don't understand what you're trying to achieve or why you think that a cello tape screen will achieve it. Perhaps I'm missing your whole point.... |
Papco_instruments
Tinkerer
Username: Papco_instruments
Post Number: 2
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 15, 2009 - 10:38 pm: |
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Perhaps lorriman is referring to placing a frosted tape over the film gate...comparing the film view with the viewfinder view.
I would second the recommendation for the Olympus single digit cameras. The finder screens were specifically designed to be user replaceable, and there are about 15 or 16 different styles available. The Oly's have about 97% full view finder. Even on the most demanding framing, they are all perfect! |
Glenn
Tinkerer
Username: Glenn
Post Number: 689
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 16, 2009 - 05:27 pm: |
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Greg's choice of camera seems to be governed by the mount type on the actual lenses he owns. I am also somewhat puzzled, as is Rick, by the '3cm' statement, however I took it as something to do with field of view accuracy and not focus accuracy.
From Greg's original statement about bokeh, I think he is looking for a screen that will show him exactly how the bokeh will appear in the finished print. Experience tells me that no screen in a 35mm slr is going to give that information with total fidelity, even the screen on a 10x8 large format can be misleading at times. However practical experience has shown which of my lenses produces the best/most pleasing bokeh, so that aspect of screen information is not the major issue to me.
Still, Greg's time and money are his own - if he wants to experiment so be it. Success or failure, he will learn something from the project. |
Eleitz
Tinkerer
Username: Eleitz
Post Number: 3
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 17, 2009 - 05:41 am: |
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Why not try an Exacta? Reasonably inexpensive, more lenses (both low end & high end)than most users can ever use & inter-changable prizims & waist level finders. |
Glenn
Tinkerer
Username: Glenn
Post Number: 692
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 17, 2009 - 01:47 pm: |
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Glen,
Sound choice - I did wonder about the Exacta, the make being quite common here in the UK where Greg and I are based. |
Lorriman
Tinkerer
Username: Lorriman
Post Number: 11
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 21, 2009 - 05:09 am: |
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Thanks for the suggestions, folks. I'll be looking in to that Exacta idea.
"Perhaps lorriman is referring to placing a frosted tape over the film gate...comparing the film view with the viewfinder view. "
That's it exactly. And it's because the view is seemingly just what I get in a final photo that I've thought to do a bit of DIY.
I think I might try wrecking that Spotmatic first; it's useless anyway. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 999
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 21, 2009 - 04:06 pm: |
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Ah, sorry, I misunderstood the whole cello-tape thing and got distracted. Basically what you want is a camera with a plain groundglass focusing screen. An early Exakta with waist level finder would be good, they came with plain groundglass screens. Eye level finders tend to have later style screens which can be truly awful (not a big issue if you're going to make your own screen, but if you get one with a groundglass you won't have to).
Another camera that might be of interest is the original series Pentacon. It came with a plain groundglass screen in its eye-level finder - not interchangeable, but as close to a piece of cello tape as you can make out of glass. Very dim around the edges (again, like your cello tape), and perhaps a bit coarse but an excellent focusing surface. And unlike the Exakta, it will accept the M42 lenses from your Spotmatic. Take special care to make sure you get one in good working order, though, they're getting old. |
Lorriman
Tinkerer
Username: Lorriman
Post Number: 12
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 23, 2009 - 02:07 am: |
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Marvellous! Thanks, Rick. I don't suppose you know of Canon FL cameras with such focusing screens (I've already ruled out the F1[n]). Two of my lenses are FL/FD mounts and I'd been using the tak smc 50/1.4 with an adaptor before I got the (faulty) spotmatic. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1000
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 23, 2009 - 03:37 am: |
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No "modern" camera had a plain groundglass, they all had some form of Fresnel field lens to brighten the screen, and generally speaking they had a microprism or split-image focusing aid in the center. Models with user-interchangeable screens usually had a "plain" screen available but it would still have the Fresnel field lens in it, and this may be what's affecting the bokeh representation (this would apply pretty much to anything Japanese). The only Canons with interchangeable screens, I think, would be the F1 and F1N models. (there was the 1959 Canonflex, but it might not work correctly with the FL lenses as its aperture coupling was different).
Another camera that I had forgotten about is the Zenit. These are M42 mount with a plain groundglass screen and you can usually find one for about 10 bucks in good working condition. This actually might be the best place to start, the cost is so low that it's worth trying just as an experiment to see if a plain glass screen is really what will fix your problem. The cameras are not very impressive to look at, but they are well made and nice to use. |
Lorriman
Tinkerer
Username: Lorriman
Post Number: 13
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 23, 2009 - 04:41 am: |
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Thanks for the great suggestion. Yes, it's quite possible that I'll find silver at the end of my rainbow and have wasted a lot of time. At least I'm enjoying it. |
Prasanna
Tinkerer
Username: Prasanna
Post Number: 8
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 23, 2009 - 04:43 am: |
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The Praktica VLC series [M42] also has interchangeable view finders, though they are not so common. Ebay UK seems to advertise a few now and then. Changing the screen on the VLC series is very easy; it is the same as the Exakta RTL1000. The Waist Level Finders are really good. Regards, subbarayan |
Lorriman
Tinkerer
Username: Lorriman
Post Number: 14
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 23, 2009 - 01:19 pm: |
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Thanks for that, Prasanna. I'll have a sniff around that possibility. |
Lorriman
Tinkerer
Username: Lorriman
Post Number: 15
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, November 10, 2009 - 09:15 am: |
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Well, much to my surprise the Zenit EM I've procured doesn't have the viewfinder I was hoping for at all. It's very much like the spotmatic: it doesn't show the depth of field beyond f2.8. At least it was very cheap and I'm pleased to have a fully battery-independent camera. |
Msiegel
Tinkerer
Username: Msiegel
Post Number: 151
Registered: 03-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, November 10, 2009 - 10:10 am: |
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My Zenit 12XP shows DOF when shutter is half depressed and thus lens is stopped down. In my case it's a Helios 44M-4 |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1009
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, November 10, 2009 - 03:00 pm: |
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I suspect that I was not precise enough - not all Zenits have a plain groundglass focusing screen. I don't have an EM, but I have an E (earlier) and an ET (later). The E has a plain, glass focusing screen, and the ET has a modern plastic screen with a microprism spot in the center. I believe for your purposes, you would need the earlier type. If your EM has a microprism screen, then you would need to look for a Zenit B or E model, I believe. Luckily, they are so cheap that you might miss a guess or two and still come out ahead (and you can resell the ones you don't want to keep)
If your EM has a plain groundglass screen (dull, not shiny on the bottom as you look in through the lens mount, and with no microprism or anything like that in the screen), and it's still not doing what you want ... then I'm afraid you're not going to find such a thing anywhere. |
Lorriman
Tinkerer
Username: Lorriman
Post Number: 16
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 11, 2009 - 02:44 am: |
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thanks, Rick. I also have an E in the post, as it happens. As you say they are dirt cheap. This one is 99p not inc. postage. Hopefully it'll do what the EM isn't.
While we're on the subject: are either of these cameras an easy take-apert-put-back-together? I was thinking of attempting the contact cleaning selenium meter repair trick. Additionally if the E is as hopeless as the EM for accurate DOF then perhaps trying to replace the focus screen with my trusty opaque sello-tape.
Ever tried repairing your E?
I don't suppose you have an opinion on the likely accuracy of the shutter after 40 years? I understand even the meters tend to be innacurate even when new: but I'm rather hoping the tank-like build means a decent shutter . |
Lorriman
Tinkerer
Username: Lorriman
Post Number: 17
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 11, 2009 - 02:46 am: |
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Rick"If your EM has a plain groundglass screen (dull, not shiny on the bottom as you look in through the lens mount, and with no microprism or anything like that in the screen), and it's still not doing what you want ... then I'm afraid you're not going to find such a thing anywhere"
Missed that. Yes, it's shiny with a microprism. Here's hoping. |
Lorriman
Tinkerer
Username: Lorriman
Post Number: 18
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 11, 2009 - 02:49 am: |
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MSeigel:My Zenit 12XP shows DOF when shutter is half depressed and thus lens is stopped down. In my case it's a Helios 44M-4
Yes, so does the EM in manual mode, but what I'm pursuing is an accurate view of the background blur rather than DOF. For my kind of photography this is a crucial element to me. I've been chasing this goal for some time (about a year) and keep finding myself down false paths. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1010
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 11, 2009 - 03:31 am: |
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My E has not needed repair; my ET came as a box of parts, and I'm afraid that to date it remains that way. They do appear to be pretty straightforward to open up, and I have some notes on it that I've gotten off of the internet (not sure if they're still up there, you might do a Google search for them).
I wouldn't waste my time on the meter - to tell you the truth, I don't even know if the meter on my E is working, I don't think I've ever looked. The shutter is a very simple system and should give good service if the curtains are in good condition. The design is the same as millions of Zenits, Feds and Zorkis that the Russians put out over the years, which all tend to be a bit unpolished but effective. |
Msiegel
Tinkerer
Username: Msiegel
Post Number: 153
Registered: 03-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 11, 2009 - 04:11 am: |
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Just digged out my Zenit 3M - plain groundglass focusing needs preset lenses and tried with different lenses.
The background blur is clearly (a contradiction) detected. Generally the longer the lens and the closer the object you focus on and the wider open the more the background is blurred.
But that's the same with 12XP - especially for what's outside the center ring.
How much that reflects what you finally see in the picture is maybe a different thing. Our brain will to a certain extent try to compensate the picture to what it's used to seeing.
I'd say that the opaque sello-tape would not be any difference to a plain groundglass - as it is normally used as a workaround if you do not have a groundglass for e.g. focus adjustment. |
