Shooting "a single maple flower"

[rjlittlefield]

This started off to be a reply over in the macro gallery, but it grew so technical, I thought it'd fit better over here in Technique.

We're talking about this single maple flower.


Nikola, the picture above is a slight crop -- 6 mm high vs 8 mm high full frame, magnification about 1.8:1 on my Canon 300D, using Olympus 80mm bellows macro lens at close to full bellows extension. Aperture was f/5.6 as marked on the lens, effectively f/16 taking the bellows extension into account. Stacked, using 25 frames at 0.005", Helicon Focus with default parameters, maybe 5 minutes to retouch stacking artifacts. No flash -- lighted by two desk lamps with 6" and 3" reflectors, about 7" from the subject. In-camera custom white balance. Slight level adjustment to compensate for deliberate underexposure when I shot the stack. (I hate shooting a whole stack and then discovering that I blew out some highlights that looked OK only because they were OOF when I set the exposure.) Slight sharpening -- mostly before resizing -- attempting to preserve the impression of what you see when you get to look closer than 800 pixels. This morning, it looks a hair oversharpened, but what the heck, I like it anyway. Here is an actual-pixels crop, straight from the camera except for the level adjustment.


Bruce, thanks for the comments. I'm glad to hear that the OOF background works as intended. I noticed when viewing through my stereo scope, that if I closed one eye, it was really hard to make sense of the flower. So I set a wide aperture to blur the background, then stacked enough pictures to get the whole middle ground sharp. With some pictures, this technique creates a distinctive "stacked" appearance, with an obvious boundary between the area where stacking makes everything in focus, and the background that's progressively more OOF with distance. In this picture, that boundary happens to be hidden behind the flower, so there's really no clue about how deeply it's stacked.

BTW, the toughest part of getting this picture was preparing and holding the specimen. These flowers come packed about 5 to a bundle, each flower with its own "stem" only about 5 mm long. Getting a single flower isolated and then held at an angle to show off the structure, while not seeing any of the holding jig, was a bit of a challenge. (Many bad words were muttered. )

Mike, what else would you like to know?

--Rik

Edit: fix typo, "8mm wide" to be "8mm high"

[Bruce Williams]

Thanks for an interesting and helpful description of your set-up and method. I am at my mothers house at the moment so am using her computer. Her screen res. is 1024X768 (at home I'm 1280X1024). Looking at your Maple flower on her screen I have to say again just how stunning this particular pic looks - the colours are amazing and the composition is excellent - altogether a beautiful "picture".

Now this may prove to be a naive question (I've never used a dedicated macro lens or bellows).... You give a step-focus figure of 0.005" - does that mean you physically rack the camera towards the specimen at 0.005" per frame? I can see how this is more easily controlled than using the focus ring on the macro lens to step through focus. However, when I rack down to step focus on my Meiji stereo scope the resulting frames always show movement and obvious scale difference. When I use my Minolta A2 (as badger's skull pic for example) I just use the focus control on the camera to refocus each frame. This results in almost nil scale or movement adjustment being necessary in CombineZM. I use these methods because I have no choice with the Mieji and no other "means" with my camera.

So (finally getting to my question ) is there a best way of working with the camera? Are there disadvantages in the "focus" method that I'm unaware of (besides calibrating step size)?

Bruce

[Mike B in OKlahoma]

Mike, what else would you like to know?

Unless you have next week's winning Lotto number, I think you covered everything!

[rjlittlefield]

So (finally getting to my question ) is there a best way of working with the camera? Are there disadvantages in the "focus" method that I'm unaware of (besides calibrating step size)?

Bruce,

Short answer: there is no single best way, and the "focus" method sounds great for what you're doing.

Long answer follows...

The easiest way to understand this issue is to think in terms of the entrance pupil of the lens. That's just the apparent position of the lens aperture, as seen from the standpoint of the subject.

In general, the best method for shooting a stack is whatever method causes the smallest angular motion of the entrance pupil, as seen by any point on the subject, as the focus is stepped through the stack.

The ideal situation is when the entrance pupil does not move at all. There are several ways that can be accomplished, but they usually require strange optics or heroic efforts, in which case they're seldom worth the trouble.

The next best situation is when the entrance pupil moves only along the line of sight, and when focus is accomplished to make it move as little as possible.

At magnifications much less than 1:1, you can step focus by changing either the subject-to-lens distance or the lens-to-camera distance. However, the entrance pupil will move far less if you change lens-to-camera. Shooting your skulls by refocusing the lens is definitely the right thing to do. (If you could lock the lens in place and let the camera move back and forth to focus, that would be perfect.)

At magnifications much greater than 1:1, you're basically stuck with changing the lens-to-subject distance and whatever happens, happens. Whether you make that change by tweaking the focus ring, or moving the lens+camera combination, or moving the subject, doesn't matter much.

At magnifications around 1:1, what's best depends on the particular lens in use. You can measure the entrance pupil movement, or just try stacks both ways and see which way works best --- assuming there's any visible difference!

Usually the worst situation (greatest angular motion) is when the lens effectively "slides sideways" across the subject. This happens with many stereo microscopes because the line of sight is tilted away from the axis of physical movement. Even that situation can be handled fairly well by current software.

FWIW, the rig that I use for most of my stacking work is described at http://www.photomacrography.net/forum/v ... .php?t=155. It works well for what I do, but there are many other schemes that work well too.

--Rik

[Danny]

That happens to be one very nice shot !!! BTW. The top one is fantastic IMHO.

Excellent work on the lighting without blowing out the details. Impressive

Danny.

[Bruce Williams]

Thanks for the explanation Rik.

I had a look at your macro rig posting - very impressive and helpfully thought provoking too. Following links (as you do) l also went on to check out your "Mayfly's eyes" posting - AMAZING!

Bruce

[Mike B in OKlahoma]

Rik--

I do have a question after all....Why did you sharpen before resizing? I've not experimented, but seems like we're always told that sharpening is the last thing you do, most especially after resizing. The few times I've resized after sharpening despite the advice, I often had trouble getting the image satisfactorily sharp again. Do you have a different experience?

[rjlittlefield]

Do you have a different experience?

Hhmm, sounds like I do.

My habits are driven by 1) making both high res prints for myself and web-resolution images for posting, while 2) using USM to partially correct for optical blurring, at all image sizes, and 3) also using USM to compensate for compression losses and monitor blurring at web resolution.

I know that once I resize, the high res option is gone forever. So I'm in the habit of doing most of my work at full resolution and resizing only at the last moment.

Generally I set up Photoshop to view at 1/4, 1/3, or 1/2 of actual pixels (whichever fits best), so I can see pretty much what the web version will look like. It's also what the print will look like, say at arm's length. At that stage of the game, "sharpening" generally means USM with a width of 1-3 pixels, and if you force me to think about it, what it's doing is probably some combination of correcting for optical blur and compensating for the eventual resize.

When I get the image looking the way I want at full resolution, with a scaled down view, I save it.

Then I make a copy and resize to web resolution. Usually I end up doing one more very light USM after resizing, maybe 15-30% with a width of 0.5-0.7 pixels, just to put in a little extra snap to feed the jpeg compressor.

I haven't tested to know whether this yields a better result than resizing and doing all the sharpening on the smaller image. But I haven't seen it giving any problems, and it leaves open more options.

Bottom line, I've had no trouble resizing after sharpening. Why that is, I don't know. One thing is that I'm pretty cautious to avoid halos and other indications of over-sharpening in the full-res version. Maybe that matters?

--Rik

[Mike B in OKlahoma]

So you are doing sharpening at full size, but you are adjusting the sharpening based on a reduced-size view, which approximates the size of your ultimate web or print image, not adjusting sharpening based on a 100% view of the full size image, right? Makes sense that that would work if I understand you right.

Thanks....This bothered me a little bit when I initially read your original post, but I had to stew over it for a day or two before I felt bugged <hee hee> enough to ask about it.

[rjlittlefield]

Yep, you have it right.

If/when the time comes to print or post a full-resolution image, then I generally sharpen once more with a much narrower USM appropriate to bring out the finest detail for that scale & medium. (Some printers require quite a lot of sharpening to make the finest detail evident -- like 100% or more at 0.7 pixel width.)

--Rik

[Cyclops]

I love this shot. I've always wanted to photograph the seemingly insignificant flowers of our trees. When you get up close to them they're quite beautiful!