MP-E 65mm f/2.8 1-5x Macro lens, nice to meet you

[Bart_van_der_Wolf]

Hi all,

I've recently decided to get (even more) serious about delving into the micro-cosmos, and I acquired the above mentioned lens. While familiar with the specifics for macro photography, I also anticipated that it would require some 'getting used to' that particular lens and its particularities.

I also knew beforehand that the limited DOF would pose some challenges, but there are software solutions that allow to tackle that.

So, I confronted both challenges, and these are my first results:



This is a composite of 6 images at different focal positions, blended together with "Helicon Focus". Because the total DOF at the optimal aperture (f/8.0) is only something like 0.14 mm (or less, depending on several factors), it requires the stacking of multiple focus plane shots to get a reasonable DOF coverage, and Helicon Focus is one of those applications that makes life a lot easier if you have to do a lot of focus stacking.

The tiny seeds shown (I've yet to identify the weed/plant species), imaged at almost 5x true size on sensor array, measure something like 1.4 millimetres in length and 0.31 mm in width. The hairs will allow for airborne transportation.

As for the artistic merit, the seeds reminded me of the Sentinels in the "Matrix" sequel, so I deliberately chose the layout as shown.

Another example of a focus stacked image is the following composite of 17 images:


This is quite a dirty version of a meat fly, dirty due to the fact that it was dead and recovered from a corner of a room that was over-due to be cleaned ...
I deliberately limited the potentially full (stacked) DOF coverage, because I wanted to simulate a 'fly in flight' situation (maybe I should also add some motion blur).

This micro-cosmos is almost as (if not more) challenging as the super-tele range. The slightest movement is magnified multifold, and there is very little light available at these extreme magnifications (5:1 magnification leaves only 1/36th of the incident amount of light), so a dedicated flash system is almost un-avoidable.

Bart

[Ivan Garcia]

Wonderful shots Bart.
I am also smitten by the MP-E65 / MT-24 combo (purchased last year fro my 40th birthday)
I have been paying around with helicon focus for a while, but my efforts are poor compared with yours.
Will you be so kind as to elaborate in the technique you employ?

[Bart_van_der_Wolf]

Originally Posted by Ivan Garcia

Wonderful shots Bart.

Thanks, but wait, I'm just getting started with this combo ...

Will you be so kind as to elaborate in the technique you employ?

Sure.

First and foremost, make sure that the individual image capture quality is optimal. Afterall, GIGO (garbage-in-garbage-out) still rules. I've tested the residual aberration/diffraction effects of my 65mm lens on my 1Ds Mark II, and decided that f/8 (only marginally better than f/9) provides the best single image resolution. Other lens/camera copies/combinations may/will lead to somewhat different numbers. Cameras with e.g. a smaller sensel pitch will most likely lead to a narrower optimal aperture. Just shoot an aperture sequence of a detailed subject, from f/16 to lower f-numbers, and choose the best one in the focus plane (disregard DOF, just go for focus plane quality).

As for exposure, and since you also have the MT-24EX Macro twin lite flash, I decided to go for manual setting rather than ETTL in the case of indoor (no wind motion!) tripod scenarios. Sometimes the ETTL will be triggered to significantly change exposure (which often works fine for handheld outdoor situations) due to subject reflection variations, but I prefer to standardize exposure for focus stacking (even though Helicon Focus can adjust for exposure differences). I also prefer to set a different exposure between the A and B flash heads, to add a more 3D look to the subject. I can check my camera's R/G/B histograms on the camera LCD for clipping, you may need to inspect the histograms in an image editor if your camera doesn't allow to do that. Check for R/G/B channel clipping on a white subject for a given magnification (magnification 'M' will change fixed exposure as (M+1)^2 , so significantly at anything above 1:1).

Focus the individual focal plane images in small incremental steps, usually going from closest to most distant. I've set the MR-24s C.Fn 9 to allow the focusing lamp to be set with the shutter release button, because the viewfinder gets very dark with large magnification factors. Switching it on/off with the shutter release button helps to speed up operations if the subject can change position. Take small focus steps, visually stepping from focus position to focus position (DOF is practically non-existing at high magnifications, so the wide-open f/2.8 viewfinder preview is a good guideline). I use a macro focusing rail for general focus position, and the lens for micro adjustments (Helicon Focus will adjust for the magnification variation due to entry pupil differences). Don't try to get full DOF coverage, retaining some very near/far out-of-focus (OOF) areas will help to convey the 3D sensation, and reduce stacking artifacts.

Focus stacking in Helicon Focus is pretty straightforward. For now, I've settled for a starting point of R=7, S=4 (may change per stacking sequence, depending on amounts of artifacts). Remember that the more extreme the DOF situation is, the more likely the artifacts will be, so limit yourself to a good DOF subject positioning to begin with.

Downsampling (and final output sharpening) of the stacked result for Web display requires some care for best quality, but that is no different from other repurposing/scaling operations.

Bart

[Paul Bestwick]

I wonder if that fly had any difficulty seeing. It seems to have dirt in about 60 of its eyes ....

[Bart_van_der_Wolf]

Originally Posted by Paul Bestwick

I wonder if that fly had any difficulty seeing. It seems to have dirt in about 60 of its eyes ....

Well, since it was a dead fly, I don't think it mattered much. I'm trying to catch a life one with red faceted eyes, but they are hard to catch.

Bart

[Ivan Garcia]

Thank you Bart.
I think you have nail it, I´ve been over enthusiastic with the DOF, and so my images look kind of 2 dimensional.
Also, the use of a focusing rail seems to be a must, so I will be looking to purchase one very soon.
Any tips as to which FR is best?, ( as in smooth and robust)

[Bart_van_der_Wolf]

Originally Posted by Ivan Garcia

Thank you Bart.
I think you have nail it, I´ve been over enthusiastic with the DOF, and so my images look kind of 2 dimensional.

Well, you can sometimes get pretty poor advice on the general WWW. In the end many things are governed by physics anyways, so diffraction is something to deal with, and single shot DOF will be limited. That's the advice you'll get on OPF ...

Also, the use of a focusing rail seems to be a must, so I will be looking to purchase one very soon.
Any tips as to which FR is best?, ( as in smooth and robust)

That depends. I've settled for a 'Really Right Stuff' (RRS) Macro Focusing Rail, because that's my system of choice. The 1DsMk2+MP-E 65mm+MR-24EX combo is quite heavy, so it really strains the MFR. There may be other suitable solutions around, also depending on your gear weight constraints.

Bart

[KrisCarnmarker]

Nice shots Bart! I especially like the top one. What mag where you at?

I've been eying the MP-E 65 for a while, but so far I've resisted the temptation :)

As for focus stacking with HF, I have had a hard time getting good results. I tend to get ghosting and other artifacts. I've never done it at this scale, but I see no reason why it would be any different. For instance, here a flower shot:



It is not all that obvious when the image is scaled down, so here's a crop:



I spent a good deal of time trying to get HF working for me, but eventually gave up. Your posted images ave given me renewed interest and I will give it another shot.

[Bart_van_der_Wolf]

Originally Posted by KrisCarnmarker

Nice shots Bart! I especially like the top one. What mag where you at?

Thanks. The images were taken at almost 5:1 (approx. 4.9:1), I like to use the last bit of extention for depth 'focusing'. If needed I could use the marcro focus rail, but small turns of the lens works fast.

I've been eying the MP-E 65 for a while, but so far I've resisted the temptation :)

I've also been able to resist for some time, afterall it is a dedicated macro lens that can only be used at 1-5x magnification and it is not cheap, but I cracked down and got it. I also knew that I'd have to address the narrow DOF issue at these magnifications, and stopping down beyond f/8 - f/9 on my camera only gains a little DOF at the expense of diffraction blur.

As for focus stacking with HF, I have had a hard time getting good results. I tend to get ghosting and other artifacts. I've never done it at this scale, but I see no reason why it would be any different.

I haven't done focus stacking on close-ups yet, only on macros. The difference is in the DOF overlap between individual images, much less backgrond/foreground blur in close-ups (should be easier if HF can differentiate between OOF areas). I'll give it a try and see what my findings are. Maybe one needs to shoot at wider apertures allowing HF to create a more accurate OOF mask, I'll test my own theory.

It is not all that obvious when the image is scaled down, so here's a crop:

Yes, it looks like you needed a larger S-parameter setting, or maybe smaller focus increments between images, and maybe a wider aperture. The more expensive HF-Pro version allows to retouch such artifacts, although it chokes on my stacked 16 MP images. I assume it's a bug that needs fixing.

I spent a good deal of time trying to get HF working for me, but eventually gave up. Your posted images ave given me renewed interest and I will give it another shot.

I have only played with HF for a short time, but I can already think of a few feature enhancements (for the Pro version) that can help in tackling such residual artifacts. I'll propose them to Dan.

Bart

[Doug Kerr]

Hi, Bart,

Fabulous work - a really great achievement.

Originally Posted by Bart_van_der_Wolf

. . . there is very little light available at these extreme magnifications (5:1 magnification leaves only 1/36th of the incident amount of light) . . .

That certainly well explains one of the large challenges of such a setup.

But let me, for the benefit of the wonks among us, point out what is really happening here. At a magnification of 5:1, the illuminance on the sensor, for any given scene luminance, is 1/36 of what the same f/number would give for focus at infinity. (Illuminance is what, together with exposure time, the sensor responds to. It is luminous flux per unit area.)

And that's basically just because the amount of light captured by the lens from any given region of the image (unchanged by a change in magnification) is spread over larger and larger areas on the sensor as the magnification increases, leading to a corresponding decrease in illuminance.

It's not really about "leaving only 1/36 of the incident light". The captured light (incident light is on the subject) is all still there. It's just "spread thin".

(I'm not at all complaining about your "metaphor", which well presents the impact of the setup - just trying to fill in some of the underlying technical realities!)

Again, congratulations on this superb work.

Best regards,

Doug