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03-07-2011, 04:20 PM   #31
axl
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Tanner,
these are absolutely impressive. I have to say you make me feel guilty for selling my FA135....
Anyway, may I ask, what are the working distances with 135 + 50 reversed on top?

03-07-2011, 04:39 PM   #32
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QuoteOriginally posted by axl Quote
Tanner,
these are absolutely impressive. I have to say you make me feel guilty for selling my FA135....
Anyway, may I ask, what are the working distances with 135 + 50 reversed on top?
thanks axl

Its all good, you have plenty of lenses that make up for the loss

Its somewhere around an inch
03-08-2011, 03:15 PM   #33
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Yeah, I know. That's the reaction I always get when people find out it was me - disappointment.

Anyway...I'm older than you (not hard on this forum) but I'm also a student.
You've got a K-7 - I don't...

What I meant is that it's just not right to own expensive equipment and then involving cheap aids in the process. If people saw it...

Must have been a pretty big praying mantis, then.
Still have to find an acceptable way to gain more magnification. MOAR!

--------------------------

newarts, what I meant to say is that it's not really possible to determine the lenses extension and the distance to the stacked lens since you would need to know the optical center of the lens (or don't you?).
But I just know the distance the stacked lens has to the priamry lens' front element.
So this is highly guesswork. You said in another thread the thin lens formulas still aplly to actual lens systems but then how to use the variables?

If I use this formula, I'd get:
(f' -d) /f" = m.stack.infinity
(105mm-30mm)/50mm =1.5

But by measuring magnifaction I got 2.3:1

I must have done something wrong with the second formula because I got m=-0,986...
Not that great.

Reusing the sum from the second formula I get
m = (m.primary.extension+1)(m.stack.infinity+1) -1 =
(1+1)*(1.5+1)-1=4

I guess I'll just leave the maths to people who know their way around them and I'll keep it practical and simply measure my results.
Hmmpf...
03-08-2011, 04:50 PM   #34
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QuoteOriginally posted by Egg Salad Quote
Yeah, I know. That's the reaction I always get when people find out it was me - disappointment.

Anyway...I'm older than you (not hard on this forum) but I'm also a student.
You've got a K-7 - I don't...

What I meant is that it's just not right to own expensive equipment and then involving cheap aids in the process. If people saw it...

Must have been a pretty big praying mantis, then.
Still have to find an acceptable way to gain more magnification. MOAR!
The only ghetto thing I use now is DIY flash diffusers. I see absolutely nothing wrong with being resourceful to get the results I desire..... no matter what camera I use. rubber bands? Why the hell not if it gives me this:



For the record, I own a K-7 ONLY because my K200d BROKE. It became unusable due to a mode dial malfunction. My options were a kx or the K-7, and for my purposes the Kx was a step backwards in key areas for macro. My parents noticing my passion for photography decided they would pitch in $200 on my 16th birthday to help me out. That was huge, and enabled me to get it. The k-7 is only a tool, and if I babied it or treated it differently than any other camera I wouldn't be able to get the shots or experience I have today. Like i said, I make due with what I got. If that means a $700 DSLR + $5 tape to reverse lenses than so be it. I will proudly show off my creations to the technique-less masses with their $2500 canon 5d's I see on a daily basis when out and about.

The mantis was of average size compared to the local stagmomantis species in SoCal. The head only shot was a crop of:



03-08-2011, 05:25 PM   #35
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Lol, no. I was ironic/sarcastic. The "..." should have implied that.

I don't care how you fix your stack-sets or what you use to produce great lighting.
If it works, it works.

For some reason I thought you were from Australia. Just saw that this is not the case. Weird.
Doesn't change anything but now I'm confused.

Still seems to be a better place to find "exotic" insects than Berlin...(see? Here they are again)
03-09-2011, 03:55 AM   #36
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QuoteOriginally posted by Egg Salad Quote

newarts, what I meant to say is that it's not really possible to determine the lenses extension and the distance to the stacked lens since you would need to know the optical center of the lens (or don't you?).
Yes, to do accurate predictions you must know the lens' "optical center" position. I use the equations more for guidance than for accurate predictions: for instance, because of the equations I know that increasing the spacing between stacked lenses will decrease magnifcation.

One can find out where a lens' center appears to be from the front by experiment; focus on a meterstick and measure the lens' magnification from the image and the known sensor width (about 23.5mm). By definition, the distance from the "lens center" to the meterstick is

distance to lens center = f(1+1/m)

This calculated distance will show you where the "lens center" is in space; it may be inside or outside the actual lens.

QuoteQuote:
....
I must have done something wrong with the second formula because I got m=-0,986...
Not that great.

Reusing the sum from the second formula I get
m = (m.primary.extension+1)(m.stack.infinity+1) -1 =
(1+1)*(1.5+1)-1=4
A step by step example of how the combined magnification equation works follows. I hope it will clarify what the various magnifications mean.

(1) Focus your primary lens at infinity (magnification=0) and stack on a close-up lens to get a magnification of 0.5x.

(2) Take off the close-up lens; you are back where you started, m=0.

(3) Now focus as closely as possible with your primary lens; say this closest focus gives you a magnification of 0.2x.

(4) With the primary lens still extended (m=0.2) add the close-up lens (m=0.5)

The combined magnification is:

m= (1+ 0.2)(1+0.5)-1 = 0.8

Hope this helps,
Dave

PS applying the d=f(1+1/m) equation is complicated because you probably don't know the actual focal length. The focal length can be determined by doing the experiment at a few magnifications and making a graph of measured distance and 1/m. The slope of the line is f and the intercept will tell you where the optical center of the lens is in space.

Last edited by newarts; 03-09-2011 at 04:10 AM.
03-10-2011, 04:37 AM   #37
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May I join this spider fest? Vivitar Series 1 105mm macro + AF360FGZ flash + spider that bit me:

03-21-2011, 10:22 PM   #38
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QuoteOriginally posted by Egg Salad Quote
Lol, no. I was ironic/sarcastic. The "..." should have implied that.

I don't care how you fix your stack-sets or what you use to produce great lighting.
If it works, it works.

For some reason I thought you were from Australia. Just saw that this is not the case. Weird.
Doesn't change anything but now I'm confused.

Still seems to be a better place to find "exotic" insects than Berlin...(see? Here they are again)
forgive me, I've never seen "...." used as a tool for sarcasm (something I spend a lot of time using )

Nope, just from a random home in the middle of suburbia in SoCal.

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