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Frost Spikes 3

 
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rjlittlefield



Joined: 06 May 2005
Posts: 727
Location: Richland, WA, USA

PostPosted: Sun Feb 12, 2006 10:48 am    Post subject: Frost Spikes 3 Reply with quote


Bald Eagle, this one's for you.

The frost was small this morning. This cluster was only 5mm wide from tip to tip.

Technical stuff: This picture is cropped from a Helicon Focus stack of 15 images, shot at 11mm field width (2X onto the sensor), using Canon 300D with a 50mm El Nikkor enlarging lens reversed on bellows. ISO 200, f/16 setting (f/48 effective), 1 second shutter.

There's not much working distance with such a short lens, but I haven't shelled out yet for a long macro setup. That's why I'm so interested in your Sigma 150 plus tubes.

--Rik

Previous posts: Frost Spikes, Frost Spikes 2
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MikeBinOKlahoma



Joined: 20 Nov 2004
Posts: 1491
Location: Umm....Could it be Oklahoma?

PostPosted: Sun Feb 12, 2006 11:28 am    Post subject: Re: Frost Spikes 3 Reply with quote

rjlittlefield wrote:

There's not much working distance with such a short lens, but I haven't shelled out yet for a long macro setup. That's why I'm so interested in your Sigma 150 plus tubes.


If you mean high magnification, and are a Canon shooter (as I am pretty sure you are), the MP-E-65 is the way to go! Wonderful lens for what it does.

What I recommend for macro and closeup work in the Canon system:

Less than 1:1--90mm TSE with teleconverters

1:1 to 2:1--180mm lens (brand of your choice) with teleconverters. 100mm macro would probably substitute if you could live with less working distance.

greater than 2:1--MP-E-65.

You do need a ring flash or closeup flash to make the MP-E-65 useable, though.
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rjlittlefield



Joined: 06 May 2005
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PostPosted: Sun Feb 12, 2006 12:31 pm    Post subject: Reply with quote

Mike, thanks for the suggestions.

Yes, I do shoot Canon, and the MP-E-65 is a very interesting lens. I'm still trying to figure out how it might fit with the spectrum of stuff that I do. A bit of guesswork, since I've never had the chance to play with one.

I'm always amused, looking at the MP-E-65 writeups, at one beautiful piece of specsmanship. The spec sheet says "Closest focusing distance: 0.24m / 0.8 ft. (from film plane to subject)". Um, yeah. Except there's a inch from the film plane to the lens mount, and the lens itself is another 3+ inches long, and...

What's the actual working distance for that beast at 5:1, anyway?

--Rik
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MikeBinOKlahoma



Joined: 20 Nov 2004
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PostPosted: Sun Feb 12, 2006 1:16 pm    Post subject: Reply with quote

rjlittlefield wrote:

What's the actual working distance for that beast at 5:1, anyway?



At 5:1, you are limited to an inch and a half in front of the lens! At 1:1, the situation improves, you can reach out a bit less than five inches in front.

The other really frustrating thing about the lens is that your DOF is nonexistent at these high magnifications. You have about 1.5mm of sharp DOF at 5:1.

These are annoying restrictions, but tolerable ones for static subjects. For living moving subjects, they become a real problem. I love to shoot ants with the thing, but they move FAST compared to that limited DOF. If I'm shooting ants at 5:1, I plan on getting two or at most three in-focus shots for every 100 I shoot. Note that I said "in-focus"; if I'm lucky, 1 in 10 of the in focus shots is actually a "good" shot!

So it is frustrating, has very limited use, requires an expensive specialized flash to be really useful, and is so limited in reach that if you're photographing ground insects you will rub the front of the flash adapter mount in the ground from time to time. Other than that, it's a great lens and a pleasure to use! Laughing

Most of these problems are pretty much inherent in trying to shoot at high magnification, though. I highly recommend the lens, but only if you REALLY want to shoot this type of thing, and are willing to live with the hassles involved.
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rjlittlefield



Joined: 06 May 2005
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PostPosted: Sun Feb 12, 2006 3:42 pm    Post subject: Reply with quote

Mike,

Thanks for the additional info about the MP-E-65.

None of this is any surprise, except that I think you're being pretty optimistic about that 1.5mm DOF at 5:1.

Let's assume you image at 5:1 onto a 22mm sensor, and from that, make a final image that's 110mm wide. Then your total magnification is Mtot = 25X, with enlarging magnification Menl = 5X.

As summarized in Ted Clarke's article, diffraction limits you to 330/Mtot^2 = 0.5 mm DOF, even if you're tolerating a pretty fuzzy result (3 lines/mm). Notice that 110mm x 3 lines/mm x 2 pixels/line = 660 pixels. This is strictly web-resolution stuff.

To get this resolution, you'll be running at an f/number of 330/(Mtot+Menl) = f/11.

Stopping down farther doesn't help -- it just makes the whole image even fuzzier. There's a reason that Canon limits you to f/16 on that lens -- they don't want people complaining that the glass is crappy, when the real problem is diffraction.

If you want a sharper image or more magnification, you have to open up even farther. Make that final image be 220mm at 3 lines/mm (1320 pixels) and you've got Mtot=50, Menl=10. You're only going to get 0.13mm DOF, and you'll need around f/5.6 to get it. Make the aperture any smaller and you get useless magnification -- diffraction blur bigger than your pixels.

Next time you have your MP-E-65 set up, run some tests and check it out for yourself. One of my friends who ran exactly that experiment with his MP-E-65 was rather surprised to see that f/16 was not his friend at 5:1.

All of the above explains why I stacked this cluster of frost spikes. I needed about 5mm total DOF for a subject that's only about 6 mm wide. But that's Mtot=18, and the best I can get in an individual frame is only 1 mm DOF at web resolution. Solution: step focus and stack 'em.

Yeah, high-magnification stuff is a pain. Those dang light waves are just too big!

--Rik
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MikeBinOKlahoma



Joined: 20 Nov 2004
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Location: Umm....Could it be Oklahoma?

PostPosted: Sun Feb 12, 2006 4:56 pm    Post subject: Reply with quote

I believe the 1.5 millimeters is Canon's (marketing-driven? Perish the thought!) statement in the manual. I think of it as being able to slice a credit card through my subject, and that works about right. Note that in this shot, the close antenna of the ant is OOF, and the ant's thorax is getting soft!

http://www.photomacrography1.net/forum/viewtopic.php?t=700&highlight=ant

And I did have the lens set on f/16! Laughing
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MikeBinOKlahoma



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PostPosted: Sun Feb 12, 2006 4:57 pm    Post subject: Reply with quote

rjlittlefield wrote:


Yeah, high-magnification stuff is a pain. Those dang light waves are just too big!


Believe me, you don't want 'em smaller....If they got smaller, they'd become ultraviolet (unpleasant) or gamma rays (downright nasty!).
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rjlittlefield



Joined: 06 May 2005
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Location: Richland, WA, USA

PostPosted: Sun Feb 12, 2006 6:46 pm    Post subject: Reply with quote

MikeBinOKlahoma wrote:
I believe the 1.5 millimeters is Canon's (marketing-driven? Perish the thought!) statement in the manual. I think of it as being able to slice a credit card through my subject, and that works about right. Note that in this shot, the close antenna of the ant is OOF, and the ant's thorax is getting soft!

http://www.photomacrography1.net/forum/viewtopic.php?t=700&highlight=ant

And I did have the lens set on f/16! Laughing

Mike,

Credit card? I'll buy that (pardon the pun) -- the ones in my wallet are right at the predicted 1/2 mm.

Your ant shot is a great picture. Very Happy

But if you check your original 3072x2048, I'll bet you see that all the detail is blurred over several pixels. (Please let me know, if that's not true.)

A larger aperture would have given a sharper image within the focus zone, but then most of the ant would have been even fuzzier. Sad

The fellow I mentioned, who discovered that f/16 was not his friend, was photographing small caterpillars for a book. He was already stacking for extended DOF. What he had not realized was that he could get considerably sharper pictures by opening up his lens, and stacking more frames.

Obviously you're not going to stack a live ant (barring some extraordinarily high speed equipment that you're not going to take into the field[*]). So for that job it's very reasonable to make the tradeoff of sacrificing some sharpness to get a usable compromise in one shot.

Different jobs, different settings.

-Rik

[*] It's not completely crazy to think of stacking a live ant. I have seen advertised a microscope system that uses an ultrasonic transducer to fly the objective up and down, while a high speed camera and very high speed image processor run the extended depth of field algorithm. I think they claim something like 20 composites per second, 50 frames each, 1000 frames/second throughput. Real-time extended depth of field microscope viewing! But portable, not yet...
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rjlittlefield



Joined: 06 May 2005
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PostPosted: Sun Feb 12, 2006 6:50 pm    Post subject: Reply with quote

MikeBinOKlahoma wrote:
rjlittlefield wrote:


Yeah, high-magnification stuff is a pain. Those dang light waves are just too big!


Believe me, you don't want 'em smaller....If they got smaller, they'd become ultraviolet (unpleasant) or gamma rays (downright nasty!).

Hhmm, now you've got me thinking again. The risk comes from total exposure: rate X duration. If you made a flash unit that put out just a brief intense pulse of short stuff, and had some properly corrected lenses...
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MikeBinOKlahoma



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PostPosted: Sun Feb 12, 2006 7:10 pm    Post subject: Reply with quote

rjlittlefield wrote:

But if you check your original 3072x2048, I'll bet you see that all the detail is blurred over several pixels. (Please let me know, if that's not true.)


Alas, it is true....Even before this discussion I knew the shot had diffraction problems. If I remember right, it is actually at f/96 or something like that. A nice f/stop for large format, but not for l'il ole 35mm!
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Bald Eagle



Joined: 12 Dec 2005
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PostPosted: Sun Feb 12, 2006 7:16 pm    Post subject: Reply with quote

Thanks Rik, WOW, it looks even better close up. Very sharp. I will keep posting shots with the Ext tubes with the 150. great working room. Very Happy Very Happy Very Happy
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rjlittlefield



Joined: 06 May 2005
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Location: Richland, WA, USA

PostPosted: Sun Feb 12, 2006 7:59 pm    Post subject: Reply with quote

MikeBinOKlahoma wrote:
If I remember right, it is actually at f/96 or something like that. A nice f/stop for large format, but not for l'il ole 35mm!

Right, effective f/stop = nominal f/stop * (1+magnification) .

And to get the same DOF effects (both geometric and diffraction), the effective f/stop should be proportional to the sensor size. So f/96 on 8x10 acts just like f/12 on 1x1.25 (35mm, cropped).

(The more times and ways I say these things, the better I understand them. If you get something useful from my ramblings, so much the better. Wink )

--Rik
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rjlittlefield



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PostPosted: Sun Feb 12, 2006 8:22 pm    Post subject: Reply with quote

Bald Eagle wrote:
Thanks Rik, WOW, it looks even better close up. Very sharp. I will keep posting shots with the Ext tubes with the 150. great working room. Very Happy Very Happy Very Happy

Glad you like it! Very Happy

The setup was a bit bizarre and I got lucky with part of it.

Basically I had the camera screwed onto a minitripod, maybe 4" off the deck, pointed down at 30 degrees or so to see the frost spikes.

It worked out just perfectly that this also placed the end of the bellows on the deck, so I had the optics rigidly supported at both ends.

That made it pretty easy to not move anything else while stepping the focus with the bellows knob. It also completely eliminated vibration so I could use the long shutter speed required by natural lighting at that time of the morning. I didn't want to use flash because I've had trouble stacking flash sequences due to slight brightness differences from frame to frame. And, uh, photofloods didn't seem like a real good idea given the subject material. Smile

I have not mentioned it before, but short focal length lenses can present a particular problem with stacking.

The issue is that as you shift focus, you also shift the center of perspective. That means that each of the stacked images is actually shot from a different position, which means that what obscures what changes a little bit from image to image.

This is not much of a problem with very low or very high magnifications, because the relative shift in position is small. But it can get very noticeable around 1:1 with short lenses on bellows. The magnitude of the effect scales inversely with the focal length, and also it is a lot less with telephoto designs that put the entrance pupil deep inside the lens. With the setup I used, I was kind of holding my breath to see if Helicon Focus would be able to handle the perspective shift. With your 150, I'm guessing the shift would hardly be visible.

--Rik
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