www.photomacrography.net :: View topic - Determining number of shots for a stack?

An online community dedicated to the practices of photomacrography, close-up and macro photography, and photomicrography.
 Photomacrography Front Page Amateurmicrography Front Page Old Forums/Galleries

 Determining number of shots for a stack? Goto page 1, 2, 3, 4, 5  Next
Author Message
bvalente

Joined: 18 Jan 2010
Posts: 69
Location: Los Angeles, CA

 Posted: Thu Feb 11, 2010 10:14 am    Post subject: Determining number of shots for a stack? I'm sure this is covered somewhere, but can someone point me to a resource on how to determine the number of shots needed to create an appropriate stack with enough DOF? After burning through a hundred shots on a pincer I think i'm overdoing it a bit I saw a spreadsheet snippet somewhere but don't know if that's generally available. Also just to clarify, I see a lot of equations, etc. on calculating various things. I am hoping there is a tool or some non-math professor way of entering in some variables and getting an answer. I am happy to put in the effort and don't expect it to be push button, but I am also not a physicist If there isn't such a thing I would be happy to take a crack at putting one together. Thanks Brian
elf

Joined: 18 Nov 2007
Posts: 1386

 Posted: Thu Feb 11, 2010 1:03 pm    Post subject: Here's a link to an Excel spreadsheet I wrote a while ago: http://www.photomacrography.net/forum/viewtopic.php?t=8054&highlight=
ChrisR

Joined: 14 Mar 2009
Posts: 8472
Location: Near London, UK

 Posted: Thu Feb 11, 2010 1:03 pm    Post subject: I expect you're looking for more info than "depth divided by depth of field"? You need to overlap the pics, by perhaps 30% but it depends on how sloppy/precise your steps are. On your PB6 you'll be having to just "nudge the knob a bit" for anything but very low magnification, and it's hard to be precise. Start in the FAQ section : http://photomacrography.net/forum/viewtopic.php?t=7359 and try the Search for similar threads and if you're using microscope objectives, Nikon's pages on DOF here: http://www.microscopyu.com/tutorials/java/depthoffield/index.html
rjlittlefield

Joined: 01 Aug 2006
Posts: 20364
Location: Richland, Washington State, USA

bvalente

Joined: 18 Jan 2010
Posts: 69
Location: Los Angeles, CA

 Posted: Thu Feb 11, 2010 1:14 pm    Post subject: Hi Rik Hm - I will have to give this some thought. you are right that in a lot of cases (well, in my case at least) i don't know the magnification. At the same time I would hope there could be a way to at least get a rough estimate. Something like - camera sensor size - bellows extension (if any) - lens focal length - lens aperture although as I think it through it would need to know how deep the subject is as well. Regarding my pincer, here's the example pic (not cleaned up, using a Nikon D300, PB-6 bellows fully extended and schneider 40mm/4.0 APO EL) I only know it as a pincer bug aka earwig, plucked from a spider's web This is shot with 202 images stacked - i may have been able to trim a few shots off each end but did that just to make sure (used a newport linear stage with micrometer to adjust the position between shots) (Also thanks for zerene stacker - just ordered it today. I'll check out your suggestion above on comparing frames) Cheers BrianLast edited by bvalente on Thu Feb 11, 2010 5:41 pm; edited 1 time in total
bvalente

Joined: 18 Jan 2010
Posts: 69
Location: Los Angeles, CA

 Posted: Thu Feb 11, 2010 1:19 pm    Post subject: Here's the full size jpg http://www.thesingingearth.com/pub/pincer_lg.jpg Cheers Brian
elf

Joined: 18 Nov 2007
Posts: 1386

 Posted: Thu Feb 11, 2010 1:53 pm    Post subject: I agree with Rik that experimenting with different increments is the best way to determine how your equipment is performing. I did the spreadsheet because I usually change the bellows draw to change the focus point instead of moving the subject. Each focus step length using bellows draw is different, whereas moving the subject the focus step length will be the same.
bvalente

Joined: 18 Jan 2010
Posts: 69
Location: Los Angeles, CA

 Posted: Thu Feb 11, 2010 1:58 pm    Post subject: Thanks elf Well, maybe there's a different tact. if I adjust my linear stage from the front to the back, I could determine how much travel distance i'd need. Then if I could calculate the DOF and factor in a % overlap, perhaps that would give me at least a starting point. I'm not looking for a scientifically accurate number, just a starting point. So for example if it told me 30 increments, i could do 40 just to be sure, at at least I'm not running 200 unnecessarily I hope that makes for a reasonable approach Brian
ChrisR

Joined: 14 Mar 2009
Posts: 8472
Location: Near London, UK

bvalente

Joined: 18 Jan 2010
Posts: 69
Location: Los Angeles, CA

 Posted: Thu Feb 11, 2010 2:15 pm    Post subject: Thanks ChrisR I understand your math and reasoning so thanks for that. I'll have to re-read it and consider. The bug was probably 5-6mm front-to-back (just eyeballing it). Regarding questions on the setup: the bellows were approx 1/3 extended. The schneider enlarger lens I have was the f4.5 version, stopped down to f5.6, non-reversed. the focus increment was approximate and by hand. I have a newport linear stage with micrometer and i twisted it about 1/8 of a turn betweeen shots. looking at the micrometer a full revolution is 45 somethings (micrometers?) so I'm guess each turn was about 8-10 of those (micrometers again?) I sure hope I don't have vibration issues. I was using a technique adapted from Charles in a dark room with 2 sec delay on shutter and rear-curtain flash. I didn't do mirror up, assuming the 2 secs would let the mirror and front shutter die down a bit. But i'm interested to know more if you think it is vibrations Cheers Brian
ChrisR

Joined: 14 Mar 2009
Posts: 8472
Location: Near London, UK

Posted: Thu Feb 11, 2010 2:32 pm    Post subject:

 Quote: PB-6 bellows fully extended

So M would have been quite a bit lower, maybe 3x. Look at a ruler though it.

Your lens would probably work better reversed - the "enlarging" configuration. The f2.8 needs a 43mm reversing ring, yours may be the same.

You may have a standard metric micrometer, 50 units per rev. That's half a millimeter, 500 microns.

220/8 = 28 turns = 14 mm. Sounds a lot

AT M=3x, and flash while the shutter's open, you should be clear of vibrations I think. Try the lens the other way about. Maybe it's diffraction...
but probably not : Your sensor is D2X size I think? http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
rjlittlefield

Joined: 01 Aug 2006
Posts: 20364
Location: Richland, Washington State, USA

 Posted: Thu Feb 11, 2010 2:48 pm    Post subject: Yep, 202 frames is serious overkill for earwig pincers. Taking your numbers... Assuming 6 mm frame width at the subject, and a 1.6 crop-factor sensor, you're working at about m=3.5. A reasonable maximum circle of confusion would be around 0.02 mm (frame width/1000), so then the standard formula would say TDF = 2 * 0.02 * 5.6 * (3.5+1)/(3.5^2) = 0.08 mm. Your pincers are unlikely to be more than a couple of mm thick if they're laid up "flat", so according to these calculations you could get by with a few tens of images. (Note the extremely high precision of this prediction. ) I see that ChrisR reaches similar numbers using a different calculation, always reassuring. Looking at your full size jpg, I see a lot of places that locally show a bit of smearing typical of vibration. But image center looks clean and flash kills vibrations, so I'm thinking the problem must be lens aberrations. At 3.5:1, you really should reverse that lens. Using it non-reversed could be a big part of the problem. --Rik
bvalente

Joined: 18 Jan 2010
Posts: 69
Location: Los Angeles, CA

Posted: Thu Feb 11, 2010 3:44 pm    Post subject:

 rjlittlefield wrote: according to these calculations you could get by with a few tens of images. (Note the extremely high precision of this prediction.

Hi Rik

Well, that is sort of my thought on starting this thread - if I could get enough basic info I could get a ballpark on where I should be (as you all have shown) so something like tens and not hundreds is actually helpful

I will definitely try the reverse lens - I thought of that yesterday and ordered the adapter ring.

On the vibration possibility, I'm not an expert so of course anything is possible. To be more specific on my setup, i used a linear stage with micrometer for the adjustments, bolted to a board. The flash was on rear curtain sync for 2 second exposure in near darkness, so I don't think vibration would have anything to do with it.

on the diffraction side of things, if I understand microscope objectives it sounds like they have much larger relative apertures and therefore would suffer less diffraction.

Getting back to my original question/post, it seems like the "basic" math and roughing things in is exactly what would be helpful, at least to me and perhaps others who are at least familiar with photography and the basics, and need a starting point. Maybe I will rough something together

Cheers

Brian
bvalente

Joined: 18 Jan 2010
Posts: 69
Location: Los Angeles, CA

Posted: Thu Feb 11, 2010 3:50 pm    Post subject:

 elf wrote: I usually change the bellows draw to change the focus point instead of moving the subject. Each focus step length using bellows draw is different, whereas moving the subject the focus step length will be the same.

elf

May I ask why would you take that approach vs moving the whole bellows/camera setup?

Cheers

Brian
AndrewC

Joined: 14 Feb 2008
Posts: 1436
Location: Belgium

 Posted: Thu Feb 11, 2010 3:57 pm    Post subject: The simplest way is often the best - shoot a stack with as fine an increment as you can manage and then start dropping images out of the stack until you see focus banding. If you aren't sure what focus banding is let us know and we will post a sample picture. Make copious notes and you will very quickly find your favourite settings and what works / doesn't work on your setup. If you find yourself constantly working with different extensions / apertures you can easily draw yourself some graphs to predict what settings to use. You really just need to shoot some stacks at minimum, mid and max bellows extension and at your chosen apertures. Takes a couple of evenings but then you will know what works for you. I keep a little cheat sheet handy which quickly lets me pick a good working step distance. Andrew
 Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First
 All times are GMT - 7 HoursGoto page 1, 2, 3, 4, 5  Next Page 1 of 5

 Jump to: Select a forum Rules and Guidelines----------------Posting GuidelinesImage Hosting Procedures Community Discussions and Announcements----------------General Discussion Forum and Community AnnouncementsCommunity Members and FriendsFavorite LocationsEquipment Exchange Image Galleries----------------Nature Photography -- Macro and Close-upTechnical and Studio Photography -- Macro and Close-upPhotography Through the MicroscopeMacro and Close-up Archives Techniques and Technical Discussions----------------Macro and Micro Technique and Technical DiscussionsEquipment DiscussionsMacro & Microscopy ArticlesFrequently Asked Questions (FAQs) Beginners Forums----------------Beginners MacroBeginners Micro Administrator's Appreciation Galleries----------------Administrator's Appreciation Gallery...Macro and Close-up ImagesAdministrator's Appreciation Gallery...Photography Through the Microscope
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum