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01-05-2009, 04:00 PM   #1
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math rationalization for LBA

No, not a formula determining need vs. want vs. insanity (though that might be a decent project). But rather a strategy of the "10mm" rule. That is primes that are about 10mm apart so that there isn't too much overlap and is enough difference in FOV to make it worthwhile. For instance I found the 31ltd and 35ltd to be somewhat redundant even though they have different character. So the new strategy:

15/4.0 ltd (whenever it is released)
CZ 25/2.8 (haven't bought this yet but looks interesting)
35/2.8 ltd (good "normal" plus close focus)
43/1.9 ltd (great long normal, fast)
CV 58/1.4 (just ordered from Cameraquest, even faster short tele)
77/1.8 ltd (fast tele, magic portrait)

Above that the 50-135* covers things nicely. If the 16-50* were as good as the 50-135*, I'd ponder just having one or two small primes...but my one copy was lousy and I'm not sure I want to try another one. Plus the primes tend to have different character so it is fun to be able to swap between them.

I suppose it isn't quite a perfect 10mm spread, but such are the realities of budget and current offerings. I just wish there was something faster at the wide end that wasn't massive (something around 20mm). I may get another 31/1.8 at some point just for the speed...if I'm feeling cash flush. Ha.

01-05-2009, 10:39 PM   #2
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QuoteOriginally posted by nostatic Quote
No, not a formula determining need vs. want vs. insanity (though that might be a decent project). But rather a strategy of the "10mm" rule. That is primes that are about 10mm apart so that there isn't too much overlap and is enough difference in FOV to make it worthwhile. For instance I found the 31ltd and 35ltd to be somewhat redundant even though they have different character. So the new strategy:

15/4.0 ltd (whenever it is released)
CZ 25/2.8 (haven't bought this yet but looks interesting)
35/2.8 ltd (good "normal" plus close focus)
43/1.9 ltd (great long normal, fast)
CV 58/1.4 (just ordered from Cameraquest, even faster short tele)
77/1.8 ltd (fast tele, magic portrait)

Above that the 50-135* covers things nicely. If the 16-50* were as good as the 50-135*, I'd ponder just having one or two small primes...but my one copy was lousy and I'm not sure I want to try another one. Plus the primes tend to have different character so it is fun to be able to swap between them.

I suppose it isn't quite a perfect 10mm spread, but such are the realities of budget and current offerings. I just wish there was something faster at the wide end that wasn't massive (something around 20mm). I may get another 31/1.8 at some point just for the speed...if I'm feeling cash flush. Ha.
Adding 10mm on the wide end is a huge difference; adding 10mm on the long end doesn't do very much. I think I'd have a problem with a gap between 15mm (too wide for many things) and 25mm (not wide enough for many things) on APS-C digital.

How about a "plus 40 percent" rule? Starting with 15mm, that gives you:

15mm
21mm
31mm
43mm
58mm (-ish)
77mm (or maybe an 85)

I think the candidates for each focal length are obvious!
01-05-2009, 10:53 PM   #3
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QuoteOriginally posted by troyz Quote
Adding 10mm on the wide end is a huge difference; adding 10mm on the long end doesn't do very much. I think I'd have a problem with a gap between 15mm (too wide for many things) and 25mm (not wide enough for many things) on APS-C digital.

How about a "plus 40 percent" rule? Starting with 15mm, that gives you:

15mm
21mm
31mm
43mm
58mm (-ish)
77mm (or maybe an 85)

I think the candidates for each focal length are obvious!
Interesting. I wonder how that happened.

I was shooting with my 16-45 tonight experimenting with different focal lengths. I have to say that I can agree with what you have but might add the 25mm to the mix. For me there is a significant difference in look between 21 and 25. I'm still not sure about 31. Though maybe a 28/2. I do love fast glass, and worry about the 3.2 being too slow on the 21. I'm often in crappy low indoor light somewhat randomly snapping. That said, some of my best shots are not through the viewfinder (shooting from the hip or away from my body, using AF) so the Zeiss would be tough for that.

Decisions...
01-05-2009, 11:17 PM   #4
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Can I get all those primes with a gattling-gun like lens adaptor so I can just spin from one to the next?

01-06-2009, 01:51 AM   #5
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QuoteOriginally posted by mithrandir Quote
Can I get all those primes with a gattling-gun like lens adaptor so I can just spin from one to the next?
would be nice, wouldn't it
01-06-2009, 03:46 AM   #6
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The only rationalization needed is that nobody ever laid on his deathbed and said, "Boy, I sure am glad now I didn't go ahead and buy that lens."
01-06-2009, 08:14 AM   #7
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Isn't there a 1.5 multiplier rule that is common?
This gives approximately
14
21
31
50
70
100
01-06-2009, 10:25 AM   #8
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QuoteOriginally posted by nostatic Quote
I was shooting with my 16-45 tonight
So you DO know what a zoom is!

01-06-2009, 10:45 AM   #9
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QuoteOriginally posted by farfisa Quote
So you DO know what a zoom is!
umm...err....*cough*

No, that is a very rare TakaNakaMura 16-45 multiprime. Made by Subaru.

Ok, to get the last joke you have to have been following a thread on the rumors board...
01-06-2009, 11:37 AM   #10
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Is it ok if I still found it funny?

I'm afraid of how much time I'd spend in the rumours forum...
01-06-2009, 12:18 PM   #11
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QuoteOriginally posted by nostatic Quote
umm...err....*cough*

No, that is a very rare TakaNakaMura 16-45 multiprime. Made by Subaru.

Ok, to get the last joke you have to have been following a thread on the rumors board...
and that lens goes to 135 mm if properly modded.

QuoteOriginally posted by farfisa Quote
Is it ok if I still found it funny?

I'm afraid of how much time I'd spend in the rumours forum...
way too much, i've been trying to catch all the threads concurrently, i should know.
01-06-2009, 12:19 PM   #12
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QuoteOriginally posted by mithrandir Quote
Can I get all those primes with a gattling-gun like lens adaptor so I can just spin from one to the next?
OK, I love this idea, however impractical, lol.
01-06-2009, 12:20 PM   #13
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Personally, the best mathematical approach to LBA is to cover every single mm if possible, and with both AF and MF, K mount and M42, Pentax and other brand.

For example:
28mm - you might get by with about 4 of these
29mm - isn't there a Russian lens with this focal length?
30mm - there's an old Pentax
31mm - there's a new Pentax
35mm - you might get by with about 4 of these
40mm - at least two flavors
43mm - definite get, new Pentax

and so on...
01-06-2009, 12:55 PM   #14
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I suppose I could also just get a dozen 300mm lenses and a ultra-precision Sawzall...
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