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10-18-2009, 04:51 AM   #1
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Pretty much a definitive page for Macro Calculations

I just happened across this page:

www.peterforsell.com

It has about every formula you might want when trying to determine everything from MFD to a simple magnification ratio using a set of tubes or reversed lens.

Some of the calcs, like MFD, will return numbers that are close but won't equate to numbers if you use the lens mfg's published MFD. MFD can vary from copy to copy as well as some makers are just conservative or even publish their MFD as front element to object distance rather than the focal plane to subject distance.....but it gets a person in the ball park.

Worth a look, hope it does not melt your brain, but the calcs are pretty simple, the concepts OTH can seem difficult but really aren't.

Here are some more pages that will help with various calculations for macro:{will add more as I find them for folks who are interested}


Last edited by brecklundin; 10-18-2009 at 05:18 AM. Reason: added more links to other calculations and even a calculator
10-18-2009, 05:28 AM   #2
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QuoteOriginally posted by brecklundin Quote
I just happened across this page:

www.peterforsell.com

It has about every formula you might want when trying to determine everything from MFD to a simple magnification ratio using a set of tubes or reversed lens.
This looks like a usefull resource. There are no calculations for F numbers etc but with ttl metering this is now largely unnecessary.
10-18-2009, 06:37 AM   #3
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Do people really do this? I have a rough idea of what gives me or less in terms of control, magnification, min. focusing distance, but really I just fiddle with stuff until it looks right and I'm pleased with the results. I guess I'll never be a REAL photographer.
10-18-2009, 06:49 AM   #4
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QuoteOriginally posted by mel Quote
Do people really do this? I have a rough idea of what gives me or less in terms of control, magnification, min. focusing distance, but really I just fiddle with stuff until it looks right and I'm pleased with the results. I guess I'll never be a REAL photographer.
Ansel Adams was meticulous in setting up and getting everything just right...how is that different? People find all sorts of ways to be interested in photography...some of us are actually mathematicians (applied as well as pure mathematicians such as myself.) and some are physics guys, others are plumbers or grocery baggers, whatever, but there are so many aspects to the hobby or even business that the more you can learn to enhance your approach, the better and, of course, the more fun and enjoyment you can get from the hobby.

Me? I like to try and take purdy pictures...hehehehe....really though I enjoy macro because I find it more technical than other forms of photography. Ya shudda seen my "franken macro" built with a Sigma 180mm with a reversed Sigma 24-60...got up to 7.5:1 mag with that bad boy...it was a BLAST.

10-18-2009, 06:54 AM   #5
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QuoteOriginally posted by brecklundin Quote
I just happened across this page:

www.peterforsell.com
Thanks, what a great link.

Last edited by audiobomber; 10-18-2009 at 07:00 AM.
10-18-2009, 06:55 AM   #6
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I like the combination of my takumar 105 with a reversed tak 35. But I didn't do any math to get it. I just play with different combinations and and remember what worked the best for what I'm trying to achieve. It seems to me that digital is more experimentation-friendly. I can play more because I have immediate results and there's no actual cost, other than time, for getting it "wrong."

And I guess being a visually oriented person, math just doesn't work for me. I go by the oooooo pretty! factor lol.
10-18-2009, 09:56 AM   #7
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I have a degree in math, and am all in favor of using it to resolve issues I can't easily resolve with my eyes. But when it comes to magnification ratios, DOF calculations and so forth, I trust my eyes more. Not that I would disagree with the numbers; just that it's hard for me to put them into any sort of frame of reference. Particularly with regard to DOF, since even the definition of what's in focus has elements of subjectivity, and DOF numbers don't tell *how* out of focus the OOF area are, which is at least as important.

Still, the numbers are useful in getting a rough idea of how equipment I *don't* own might comapre to equipment I *do* own. So if I know (as I do from empirical observation, not math) that my current Raynox 150 + M135/3.5 gives me 1:1, I can then use this information and some math to get an idea of how it compares to other lenses (by seeing what calculations the formulas yield for working distance, DOF or other matters that might be of interest).

Which is to say, the math doesn't help me use my current equipment better, but it might help me in choosing new equipment.

Last edited by Marc Sabatella; 10-18-2009 at 05:22 PM.
10-18-2009, 11:14 AM   #8
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QuoteOriginally posted by audiobomber Quote
Thanks, what a great link.
Thanks!! Cool that ya like it!! It never hurts to have more tols to help understand whatever it is we think we are trying to do....hehehe!!

QuoteOriginally posted by mel Quote
I like the combination of my takumar 105 with a reversed tak 35. But I didn't do any math to get it. I just play with different combinations and and remember what worked the best for what I'm trying to achieve. It seems to me that digital is more experimentation-friendly. I can play more because I have immediate results and there's no actual cost, other than time, for getting it "wrong."

And I guess being a visually oriented person, math just doesn't work for me. I go by the oooooo pretty! factor lol.
Mel....read my answer to Marc below and you will see I am the same. I shoot only by feel. I might do what I call some 'numpty' shooting (named after a fun leetle app/game called "Numpty Physics". And while I really do try and plan my studio product shots as well as I know how at this microsecond in time, eventually the numbers only tell us so much...I feel they are merely a starting point. After that I have to trust my eye, for whatever that might be, or, ummmm, not be worth. HAHAHA!! I was spoiled with my Canon gear because I was so dialed in with it but I NEVER truly felt I was the one taking the pictures. With my new Pentax gear, I feel like I am actually part of the whole creative process. Dunno if that is good or bad but as long as I have fun that is all I care about.

QuoteOriginally posted by Marc Sabatella Quote
I have a degree in math, and am all in favor of using to resolve issues I can't easily resolve with my eyes. But when it comes to magnification ratios, DOF calculations and so forth, I trust my eyes more. Not that I would disagree with the numbers; just that it's hard for me to put them into any sort of frame of reference. Particularly with regard to DOF, since even the definition of what's in focus has elements of subjectivity, and DOF numbers don't tell *how* out of focus the OOF area are, which is at least as important.

Still, the numbers are useful in getting a rough idea of how equipment I *don't* own might compare to equipment I *do* own. So if I know (as I do from empirical observation, not math) that my current Raynox 150 + M135/3.5 gives me 1:1, I can then use this information and some math to get an idea of how it compares to other lenses (by seeing what calculations the formulas yield for working distance, DOF or other matters that might be of interest).

Which is to say, the math doesn't help me use my current equipment better, but it might help me in choosing new equipment.
Cool you found this there, was hoping you would because I knew you also had at least one degree in math. Like I mentioned mine are in "pure" mathematics (I know you will understand what that means, others, well look it up...but in essence it means I am not comfy with real world uses of my equations, I just like solving the systems for their own sake...let the engineers and others figure out what to use them for, not my problem!! )

But, Marc, I also hoped you would see the use of these equations as tools but not the end all of the process. I like that a lot of your comments about your shots are of the thought process and where it matters you mention what part some calcs might , or might not, have played.

For me in macro shooting all I really care about is the MFD. Something I did learn was Pentax kinda lied to me, but not really...other companies like say, Sigma usually report the MFD for a macro based on objective to subject distance. ON my 35ltd macro it is apparently the actual MFD from the focal plane...meaning I ended up with over 3" less MFD than I assumed from the numbers on the Pentax data sheet for the lens.

I haven't tried a Raynox simply because I don't want the IQ loss. So I avoid the bees (I need an epipen when I am out and about...and they seem to KNOW it, I think some are epi-addicts! hehehehe....)

I'm also looking forward to playing with the equations on the page just because. I want to really compare to the results returned from the link to the Macro Calculator. Until now I have just been using the simple stuff for figuring out mag ratio using tubes or a reversed lens. I will tell ya that 180 macro with the 24-60 reversed was just more fun that I expected. Remember the formula for the ratio is simple:

Mag Ratio = focal-length of primary lens)/(focal length of reversed lense).

In a nut shell that equation tells us that the longer the primary lense the way to get a higher ratio is to use a SHORTER reversed lens. If one has, say a 100mm macro, if you also have a 17-70mm reversed lense the mag ratio will go from 100/17= 5.9:1 ratio...that is HUGE and on the 70mm end you get (100/70)= ~1.5:1. So the ratio is adjustable between ~1.5x up to ~5.9x...even a 50mm reversed will give a 2:1 ratio. A reversed lens, especially a fast-ish f2.8 zoom is a nice way to get higher ratios on the cheap. Even fast wide primes are nice too, only not as easy to change in the field, and once I did done enough macros, I learned it can get pretty dusty & dirty fast... I need to pick-up a set of 49mm male-male adapter rings so I can get a bit over 2:1 with my 35ltd reversed on my 77ltd...THAT should be "interesting" for sure!

Those numbers give us using Pentax gear something very close to the best macro around and that is the Canon (yeeeah, I know) MP-E 65mm which comes out of the box as a 1x-5x lense. Thing is it's a special purpose lense so one needs to really be dedicated to macro to justify buying it.

Pentax has the advantage of all these old MF lenses with aperture lenses that are CHEAP...who cares what mount they have, as long as the lens is fast. I was getting pretty nice shots, ok, interesting shots using a reversed zoom lens rather than a reversed prime.

The thing to consider and be aware of, is it is possible to move the MFD behind the front element...generally that is a bad thing...hehehehe...

Until I found that page this am/last night, I had not found a set of equations to allow calcs to approximate the MFD for a given setup. That is where I look forward to trying them out when I am in a macro kinda mood. You are lucky because where you are there are all sorta creepy crawly beasties to get up close and personal with...I would LOVE to come across one of those brightly colored, almost florescent "forest slugs" and make a day of shooting the critter...

So, please post anything you find out for your gear...we need more technical and also non-technical discussions about macros. Macro is not a "black art" as many think. It is, as you mention just as easy to simply learn the limits and character of your glass.

Oh, something many don't know, this is a trick I leaned a while back, you can just hold a lens up against the body mount and snap a shot if you don't have a reversing ring...duct tape, or even better gaffers tape (less residue) will work well enough to let you focus and adjust the aperture for a session. Results won't be perfect, usually, but they work.

One of may most admired macro shooters, Brian Valentine from the UK, has this sure cool "Bean Pole" technique he uses to steady his camera to get some of the best macro shots a person could ask for...I'll post a link but you can also search on "lordV bean pole" to find info...here are some shots of Brian and his setup (but he has articles and even better lots of shots all over the net):

LordV's - Me, cat and macro rig on Flickr - Photo Sharing!

I better stop, not sleep yet and I tend to ramble a LOT more than normal when i haven't slept...two nights ago, Friday night some idiot did a hit and run on my vehicle in my carport no less...bastage, and yesterday I learned it;s actually near $5k in damage even though it looked superficial. Nice thing was there were eye witnesses who got the license plate and the cops found the vehicle that might. But it's been sort of a hectic last couple months and this sorta capped it off....see there I go rambling AGAIN...plus I really do not like insurance companies! And now I have to deal with them, the cops, the DA and my own attorney as I am gonna nail the SOB in civil court for the willful negligence in running away from the scene of an accident. OK, rant over back to macro... hehehehe....

I will just end with, moving to Pentax really made me realize something so basic, old fast primes and faster, f2.8, zooms with a manual aperture ring are a super reversing tool and less bulky than a bellows.

10-18-2009, 11:20 AM   #9
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Wow! Those articles are much too complicated for me ...I just use my DOF preview to judge how thinks will look. I might bracket a bit for DOF anyway just to make sure.

Mike.
10-18-2009, 11:28 AM   #10
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For what it's worth, we (BrendanPK and I) did just revised an little blurb I wrote on his news and reviews website on cheap macro to include a link to this website for those that might care about the math part. It is fascinating. It's just that my ooo pretty brain can't process it. I can see however where it would be useful in a situation where things HAD to be just so, it's a one-time only shot, and you need to figure out what gear to use ahead of time. If I ever have that situation I'll ask Marc and his math degree.

And Brecklundin - tell me about the insurance co thing. I was robbed in early Aug and I FINALLY got some resolution from it last week.
10-18-2009, 11:37 AM   #11
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QuoteOriginally posted by MikePerham Quote
Wow! Those articles are much too complicated for me ...I just use my DOF preview to judge how thinks will look. I might bracket a bit for DOF anyway just to make sure.

Mike.
hehehehehe..that made me grin...really...and I know it looks complicated but basically the equations are just "plug and play" all you need to do is know what each term represents then you can just plug them into the equation to get your result. If you have any probs with doing any algebra to "solve for x" just post it and either myself and maybe Marc (and I KNOW there are others) who can help.

Also if you notice, there is also a link in that same post to an online calculator for many of the values. Though I suppose figuring out what the numbers mean in relation to each other can seem difficult...really they are not that bad.

So, take another look and also look at the calculator, maybe google some of the terms and take your time...it might turn out that understanding the more technical relationships between the values can help one understand the characteristics of their lenses.

My most rewarding thing I ever did mathematically was help a 75yr old woman understand fractions (I taught a basic arithmetic at a local JC to help pay for more school.) The look of sheer joy on her face was amazing, she really reached a milestone in her life. And it made me feel, for the first time, like what I knew could help others learn...what a feeling and I let her know how wonderful she made me feel. If that is possible, you can do this easily enough, you just need to want to and get past the complicated LOOK of the equation terms...
10-18-2009, 11:45 AM   #12
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QuoteOriginally posted by mel Quote
For what it's worth, we (BrendanPK and I) did just revised an little blurb I wrote on his news and reviews website on cheap macro to include a link to this website for those that might care about the math part. It is fascinating. It's just that my ooo pretty brain can't process it. I can see however where it would be useful in a situation where things HAD to be just so, it's a one-time only shot, and you need to figure out what gear to use ahead of time. If I ever have that situation I'll ask Marc and his math degree.
Go ahead and post a link...it would be fun to read!!

QuoteQuote:
And Brecklundin - tell me about the insurance co thing. I was robbed in early Aug and I FINALLY got some resolution from it last week.
THAT is a very frustrating thing...I was robbed when moving bavk to my home town to care for my Mom back around '95. The bastages got over $30k worth of tools, computers and such (ironically they left my signed original Icart's just sitting on my couch and they were NOT insured because I had not added a rider to cover them. They are worth 2-3x the stuff they did take and worth even more than the dime on the dollar they would get from a fence. That night I learned I was lucky, the cops told me these sorta guys like to leave, well, a "calling card" in people's beds...EWWWWWW...I never saw a DIME because the insurance company fought tooth and nail since the policy was only a few months old...finally I just gave up and did not even hire an attorney because, well, no way I would have seen a fraction of what I was entitled to after the vampire, er, attorney took his cut and expenses.

But this one is pretty cut and dry, though I did find out the the drivers son or father (I don't recall which the witness said) is also a cop....great...
10-18-2009, 12:24 PM   #13
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Unlike you "mathematicians" who do maths for the sake of it, my first degree is in experimental physics so I do mathematics when only I need to. I am curently undertaking a part time PhD in opitical physics (specifically designing and building a digital macro imaging instrument which used tilt movements - this requires a lot of working out). Between this and my engineering training I have developed quite an interest in fixing and building my own equipment.
For the most part, slr photography does not justify working things out mathemitically first, only for some macro setups. However I am currently converting an old Ilford / Kennedy instruments monobar view camera ( I had a peaceful afternoon in my shed working on this today) to take my DSLR and setting up a vew camera properly can take a lot of working out.
On a macro related note I found (and brought) a pentax microscope adapter yesterday (the genuine Asahi one shown here: http://kmp.bdimitrov.de/lenses/adapters/microscope.jpg). This should allow some interesting technical high resolution macro photography.
10-18-2009, 01:17 PM   #14
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QuoteOriginally posted by MattGunn Quote
Unlike you "mathematicians" who do maths for the sake of it, my first degree is in experimental physics so I do mathematics when only I need to.
Please tell me you do it in private and wash your hands after you're done!!

QuoteQuote:
I am curently undertaking a part time PhD in opitical physics (specifically designing and building a digital macro imaging instrument which used tilt movements - this requires a lot of working out). Between this and my engineering training I have developed quite an interest in fixing and building my own equipment.
For the most part, slr photography does not justify working things out mathemitically first, only for some macro setups. However I am currently converting an old Ilford / Kennedy instruments monobar view camera ( I had a peaceful afternoon in my shed working on this today) to take my DSLR and setting up a vew camera properly can take a lot of working out.
On a macro related note I found (and brought) a pentax microscope adapter yesterday (the genuine Asahi one shown here: http://kmp.bdimitrov.de/lenses/adapters/microscope.jpg). This should allow some interesting technical high resolution macro photography.
I agree that the calcs are not really needed for the most part, but that is only because almost all of them have been done already and can be looked up.

Your microscope adapter sounds like a fun experiment...hope to see images soon...keep after than PhD...it an be frustrating but get it...opens so many doors. A person with a PhD in Physics can do anything, travel and teach here and there as a visiting a instructor/prof...and you can even teach math if that is all that is there. It's always fun to get into the chicken-egg debate about math v. physics, which came first...given my chosen area ya know where I stand....hahahaha....physicists do very mean and evil things with our beautiful elegant equations!!
10-18-2009, 05:33 PM   #15
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QuoteOriginally posted by brecklundin Quote
Cool you found this there, was hoping you would because I knew you also had at least one degree in math. Like I mentioned mine are in "pure" mathematics (I know you will understand what that means, others, well look it up...but in essence it means I am not comfy with real world uses of my equations, I just like solving the systems for their own sake...let the engineers and others figure out what to use them for, not my problem!! )
Same here. I was really into number and group theory, as I recall. I was gonna be the guy to prove Fermat's last theorem (yeah, right). Seems like a distant past life - I barely remember any of it now. It is indeed, as you suggest elsewhere, more about the process of logical thought that I feel I continue to put my math background to good use.

QuoteQuote:
For me in macro shooting all I really care about is the MFD. Something I did learn was Pentax kinda lied to me, but not really...other companies like say, Sigma usually report the MFD for a macro based on objective to subject distance. ON my 35ltd macro it is apparently the actual MFD from the focal plane...meaning I ended up with over 3" less MFD than I assumed from the numbers on the Pentax data sheet for the lens.
That confused me when I say the numbers on Dimitrov's site showing the 100mm macro having a minimum focus distance greater than I was getting with my M135/3.5 + Raynox 150. I'm now assuming that this is the reason. I could work through the numbers, but I'm content to just assume in this case :-)

QuoteQuote:
I haven't tried a Raynox simply because I don't want the IQ loss.
??? Have you followed the Raynox thread? Used with a good lens to begin with, you'd really be hard pressed to see a drop in IQ compared to the other methods you might be considering. On the other hand, if you're OK with reversing rings and so forth, it's not like there's any real advantage in the Raynoxes, either. Revering rings do gie you a lot more flexibility if you've got a variety of lenses you could use them with.
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