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Optics Theory - This forum is aimed towards the TECHNICAL side of photographic OPTICS THEORY. There will be some overlap by camera/manufacturer, but this forum is for the heavy duty tech discussions. This is NOT the place to discuss a specific lens or lens line, do that in the appropriate forum. This is the forum to discuss optics or lenses in general, to learn about the tech behind the lenses and images. IF you have a question about a specific lens, post it in the forum about that type of camera, NOT HERE.

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Hi Mike
Old 03-04-2008   #41
ampguy
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Hi Mike

I specifically went around shooting objects close up and wide open:

http://matsumura.smugmug.com/gallery...xbjR#255483561

You do need some kind of contrasting patch, but I find that is necessary with most lens.

The M6 focuses it easier, but by no means is it not possible to focus close up and wide open on an RD1, in my experience.

Next beer get together, I'll give a master class in "Focusing the 75/1.4 Lux"


http://matsumura.smugmug.com/gallery...xbjR#255483561

Quote:
Originally Posted by MikeL
Ted, are you framing your subjects for the 75mm like you would with the 50mm? (i.e. farther away from your subjects with the 75mm)
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Old 03-04-2008   #42
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Quote:
Originally Posted by ampguy
Next beer get together, I'll give a master class in "Focusing the 75/1.4 Lux"
Well, it might be the cigarettes, coffee, beer and other vices, but I have even
difficulties on the M6. The M3 is the right base for bertha
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Old 03-04-2008   #43
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Quote:
Originally Posted by ferider
...Note that the above table does not account for minimum focus. For example, the 135/2.8 focuses down to 1.5m (? out of memory)...
Do you refer to the Elmarit 135/2.8? If so the minimum distance is indeed 1.5 meter but i wonder if your table takes its goggles into account on Leica M cameras.
Great job anyway.
Edit: Not sure if the goggles mag. is 1.4x according to Cameraquest or 1.5x according to my aging memory.

Last edited by LCT : 03-04-2008 at 21:46.
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Old 03-06-2008   #44
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Just curious, what would it take to show you folks that I can focus the 75/1.4 lux on the RD1 at f2 with 99% accuracy, and maybe you will consider gradients instead of making Bessa owners mistakenly think that long lenses wide open are impossible to focus accurately?
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Old 03-06-2008   #45
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Quote:
Originally Posted by ampguy
Just curious, what would it take to show you folks that I can focus the 75/1.4 lux on the RD1 at f2 with 99% accuracy, and maybe you will consider gradients instead of making Bessa owners mistakenly think that long lenses wide open are impossible to focus accurately?
I agree, Ted. I really don't know why people don't seem to believe us when we say that using the 75 Summilux at f1.4 on the R-D1 is not that hard, especially with a magnifier. I thought that rangefinder base length was only a relative guide, not absolute. In fact, I got the 75 Summilux for the R-D1 despite common knowledge regarding the R-D1's short base length and very little being written on the combination. I don't care whether someone decides to get the lens or not, but I hate to see this great combination be maligned and people dissuaded from it due to skepticism and fear rather as opposed to real user experience (including experience other than one's own).

Last edited by edhohoho : 03-06-2008 at 10:30.
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Old 03-06-2008   #46
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Guys, the table shows that 75/2 is focusable on RD1 with magnifier, and R3 without. Plus a digital camera always allows you to check if you hit focus. - a huge advantage.

Nobody maligns anything. The table just shows values of a mathematical text book approximation. It does not include that focusability is highly minimum focus, person and camera body dependent (backlash). And not everybody focuses the Summilux at .7m (I do though). At minimum focus that lens has around 1cm DOF (on film) ! At infinity, you can focus any lens on a body with 0 EBL.

LCT, you are right, the 135/2.8 googles amplify by 1.5 ( = 135/90). Should correct that in the next version of the table.

Roland.

Last edited by ferider : 03-06-2008 at 10:38.
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Thanks Ed and Roland
Old 03-06-2008   #47
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Thanks Ed and Roland

The thing is, that I can absolutely 100% focus at f2 on the RD1 close and wide, and 99% @ 1.4 if I concentrate (give me 20 seconds and something of contrast, just as what I would need with an M3 with magnifier...).

I think it's a little bit wacky to do these binary thumbs up/down, green red, when *without* magnifier I can certainly focus some of these lenses at the specified thumbs down or red areas.

I think your taking "e" or "m" values for granted as constants might be throwing you guys off.

If I were new to rangefinders and saw your charts, I'd run away from Bessas, but having used them, I know they're capapble with my eyes, and my aligned lenses and bodies, of critical focus in some of the red areas.


Quote:
Originally Posted by ferider
Guys, the table shows that 75/2 is focusable on RD1 with magnifier, and R3 without. Plus a digital camera always allows you to check if you hit focus. - a huge advantage.

And not everybody focuses the Summilux often at .7m (I do though).

Roland.
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Old 03-06-2008   #48
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Quote:
Originally Posted by ferider
Guys, the table shows that 75/2 is focusable on RD1 with magnifier, and R3 without. Plus a digital camera always allows you to check if you hit focus. - a huge advantage.

And not everybody focuses the Summilux often at .7m (I do though).

Roland.
But I believe some of us are saying that it is possible to focus the 75 Summilux at f1.4 and f2.0 without a magnifier. Even with a magnifier, it is more than possible to use the 75 Summilux at f1.4 because that's the aperture at which I most often use it. Regardless, I'm happy with my experience with the 75 Summilux and the R-D1 whether you think it's real or just dumb luck.
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Old 03-06-2008   #49
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Here's another question for you graph makers:

What are the symptoms or feedback to the user of not being able to focus accurately?

Does it appear to focus in the vf, but the image comes out unfocused? Is it back focused or front focused, or does the image just come out black?

Or does the an LCD sign show in up the VF saying "Sorry, invalid range for this cheapo camera and that f-stop, try another"
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Old 03-06-2008   #50
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No free beer for you at our next get together, Ted I think you should finally get yourself that M8 ....
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Hi Roland
Old 03-06-2008   #51
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Hi Roland

On second thought, (just played with dofmaster), I think the values may be right, I get 1cm of DOF at 1m @ f1.4 with the 75mm on the RD1.

This is what I notice, I have to pick whether I want the nose or eyes or ears in focus at min. focus on both people and especially the cat, and realize that if I move off center that I'm likely moving out of that 1cm range.

I guess I could take a sequence of 20-30 or more photos and show you that I capable of getting most right on at f1.4, or all of them (unless some major operator error) at f2.0 with the 75/1.4 lens.

If you added +/- 5 or 10% into your calculations, would the RD1 without magnifier be green at f2.0 with 75mm?

If so, maybe a yellow color or thumbs sideways at +/- x %??
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Lol!
Old 03-06-2008   #52
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Lol!

Well we should do the focusing demo before the beer

I think the M8 doesn't have enough pixels. We just got back a 20" x 30" $9.95 poster from Costco from the kids 7MP A550, so I think there may be something to big enlargements and huge amounts of pixels.

The quality of this poster image is equal to that of those Paris/Britney ones at Kmart, very sharp.

I think I need 12MP, am looking at the A650IS and S950IS, I don't need the G9, that has raw mode, I don't do raw.

Quote:
Originally Posted by ferider
No free beer for you at our next get together, Ted I think you should finally get yourself that M8 ....
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German or Canadian?
Old 03-06-2008   #53
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German or Canadian?

Ed, is your 75/1.4 lux German or Canadian?

I'm possibly on the verge of exposing a major theory, second only to the Kennedy one...

Quote:
Originally Posted by edhohoho
But I believe some of us are saying that it is possible to focus the 75 Summilux at f1.4 and f2.0 without a magnifier. Even with a magnifier, it is more than possible to use the 75 Summilux at f1.4 because that's the aperture at which I most often use it. Regardless, I'm happy with my experience with the 75 Summilux and the R-D1 whether you think it's real or just dumb luck.
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Much better Roland
Old 03-06-2008   #54
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Much better Roland

Showing the #'s is interesting - should the CL with 50/1 really be at ~ 132%, while the 75/1.4 on RD1 at 158%.

I haven't used the Noctilux on the CL, but had more of a hit/miss ratio with the CL and 40/2 @ f2, than the RD1s with 75/1.4 @ f1.4, but not sure it was EBL, might have been smaller VF patch on the CL.

Anyways I think it's a very interesting table you guys did, and I am just considering myself lucky being able to get good focusing in some of these borderline areas.
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Last edited by ampguy : 03-06-2008 at 11:42.
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Old 03-06-2008   #55
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Next meet up Ted, if you don't accurately focus the 75mm 90% of the time, the first round is on you. No drinking before the test either. We'll announce this before hand and we'll be guaranteed to have a good turn out. Free beer!
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Old 03-06-2008   #56
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Quote:
Originally Posted by ampguy
Ed, is your 75/1.4 lux German or Canadian?

I'm possibly on the verge of exposing a major theory, second only to the Kennedy one...
German, serial number beginning in the 39 range.

I think I may have caught a glimpse of your theory in another thread...
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Sure Mike!
Old 03-06-2008   #57
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Sure Mike!

I think you also mean @ min. distance, not infinity, right?

I'll need a stationary object, a bit of light, and something with some contrast, even one of those dslr focus test charts would work. You want to up the stakes a bit??

Quote:
Originally Posted by MikeL
Next meet up Ted, if you don't accurately focus the 75mm 90% of the time, the first round is on you. No drinking before the test either. We'll announce this before hand and we'll be guaranteed to have a good turn out. Free beer!
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Ok
Old 03-06-2008   #58
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Ok

Well I'll just state facts so as to not start unfounded rumours:

Fact 1: Erwin Puts says the German flanges are a different ligheter material than Canadian 75/1.4's.

Fact 2: Different materials can have different thicknesses.

Fact 3: Different flange thickness can affect focus accuracy.

I'll leave the technical conclusions to the engineers


Quote:
Originally Posted by edhohoho
German, serial number beginning in the 39 range.

I think I may have caught a glimpse of your theory in another thread...
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Old 03-11-2008   #59
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As mentioned earlier I thought I would post my reference - on page 223 of the Osterloh Leica M Advanced book, v2 (2005), it mentions that the DOF scales of Leica M lenses, and viewfinders of the M2, and M3 are based on a coc of 1/30mm which is .033333333, making the RD1 possibly .02222222 giving a few more greens and yellows, for example, making the CL and the optional kit tele 90/4 now green (97%). I sitll think the basic premises are missing something, maybe a VF patch readability factor or inclusion of a factor for min. dist. as the low % for CL and 40/1.4 amazes me.

Still, I think it is a very useful graph that Roland, LCT, and the others have done. The curves chart (latest one) is also interesting.
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Old 06-28-2008   #60
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sticky please? maybe move to the lens/optical section?
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Old 06-28-2008   #61
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Done.

Kim

Quote:
Originally Posted by ampguy View Post
sticky please? maybe move to the lens/optical section?
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Old 01-19-2009   #62
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Thanks, I think Roland and LCT did a great job with this tool. Answers a lot of questions on what combo is usable, although there will be exceptions with different peoples eyes, alignments, etc. I've saved a local copy and have referred to it dozens of times sometimes adding my own tweaks.
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Old 01-19-2016   #63
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Contax G1 has 41mm
G2 52mm
IIa+IIIa 72mm
II+III 92mm in base length.
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Old 03-30-2016   #64
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Here is a link to the spreadsheet from a few years ago.

RF Accuracy Chart
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