Suggestions for improvement - macro bugs with Zerene

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clarnibass
Posts: 130
Joined: Fri Jun 10, 2016 11:33 pm

Suggestions for improvement - macro bugs with Zerene

Post by clarnibass »

Hi

First time I use my electric rail and trying to take a photo of a bug. So far my macro photos have only been of stuff like small industrial parts (tiny screws, springs, rust, etc.).

I'm looking for some suggestions on how to improve. The main problem is that at 100% it's a bit less sharp than I hoped it would be and the stacking has some halos and a few other issues (I use Zerene).

The light was just a front flash (attached to the camera) with a small soft box. I think I'll try flash (attached to camera) bounced from a larger white or silver reflector. I can use the flash not attached too, no problem, but not sure it would be better in this case(?).

The camera is a Nikon D600 and in this test it's just 1:1 magnification with a Nikon 105mm Micro lens which is supposed to be very sharp. I used f/5.6, which is just 1/3 of a stop smaller than wide open (at 1:1 it's f/5, even though the lens is f/2.8 ). According to the calculator I found this is approx f/11. I wasn't sure what aperture is best to use considering the lens aperture and the actual aperture.

I checked both white and black background and black seems better. Maybe moving it farther back would help with the darker halo around the bug.
The problem with the white background is a lot of the details around the bug disappeared, but maybe it will be better with farther back white background and the different (softer) light?

This is just practice tests, with the goal to eventually (I have about six months for it) take photos of a significant number of bugs in a local museum collection.

Image

hero
Posts: 72
Joined: Mon Jul 17, 2017 12:38 pm
Location: California

Post by hero »

Something to understand about your lens on Nikon bodies is that the aperture that the camera reports is the effective f-number, not the nominal aperture. In other words, the Nikon system (at least for your specific lens, not sure about others) has already done the calculation for you, and you should not be calculating an effective f-number from this value.

An easy way to confirm that this is happening is to focus the lens to infinity while in aperture priority or manual exposure mode, and then focus it at 1:1, and watch how the reported f-number changes.

As for improving your photos, I think lighting is a critically important aspect of good close-up photography. The lighting shown in your image seems to suggest a direct light source without any diffusion. This may be your intended effect, but the result exhibits very strong contrast with lost shadow details in the subject.

Another issue not typically encountered in other types of photography is that dust and fibers become much more visible and distracting. Whole chapters could be written about techniques to clean insects, never mind other types of small subjects. Live insects tend to groom themselves, but dead ones seem to accumulate dust at an incredible rate. A museum collection, well-kept and maintained, should be reasonably free of dust.

clarnibass
Posts: 130
Joined: Fri Jun 10, 2016 11:33 pm

Post by clarnibass »

Thank you.
hero wrote:Something to understand about your lens on Nikon bodies is that the aperture that the camera reports is the effective f-number, not the nominal aperture. In other words, the Nikon system (at least for your specific lens, not sure about others) has already done the calculation for you, and you should not be calculating an effective f-number from this value.
Oh I see my mistake. I thought that the f/5.6 that the lens shows (supposedly set to f/3.2) is what I put in the calculator to check effective aperture. I thought it was something else in addition to the effective aperture, didn't realize it was the effective aperture itself. So I guess as long as I use the lens attached to the camera I can go based on that, and not worry about diffraction up to probably around f/11. So reducing the aperture may have helped in this example. I more often use the lens with manual extensions and not used to seeing the aperture on the camera, so got confused.

hero wrote:As for improving your photos, I think lighting is a critically important aspect of good close-up photography. The lighting shown in your image seems to suggest a direct light source without any diffusion. This may be your intended effect, but the result exhibits very strong contrast with lost shadow details in the subject.
Thanks, I'll try the more diffused light first and see how that looks. It does have a diffuser now but it is pretty small.
I also read in another thread that using both pmax and dmap and masking different parts is sometimes the best option. I haven't had to resort to this with what I did before, but dmap does have a lot less of the outer halo.
hero wrote:Another issue not typically encountered in other types of photography is that dust and fibers become much more visible and distracting. A museum collection, well-kept and maintained, should be reasonably free of dust.
Yes this beetle went through a lot... a few apartment moves and standing in an open room for a few years, sometimes squashed in a random pile of stuff :)
Yes they keep them under glass in drawers (actually it's a lab and most of the collection is not even on display). For many of the bugs they have more than a few of each so I can choose the best one.

Thanks again

Chris S.
Site Admin
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Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

Clarnibass,

A few easy changes will likely result in a quantum leap up in quality.

Of lesser importance, but very easy to do, is to stop down your lens a little bit. My micro-Nikkor 105/2.8 AF-D, when shooting at 1:1, is sharpest at f/11 as reported by the camera. As you and Hero have discussed, Nikon bodies report effective aperture. So effective f/11, at 1:1, is likely somewhere around f/5.6 nominal--about 1.5 to 2 stops down from wide open. To test your own lens' best aperture for various magnifications, you can do "aperture sweeps" (careful tests at each aperture, and the halfway points between), and take notes.

Of greater importance is your lighting. (The bug you posted has very bright highlights and is not evenly illuminated; and believe it not, even lighting not only contributes to a more pleasing image, but with shiny subjects, it can also increase sharpness considerably.) As a good general lighting recipe for shiny bugs, start with very broadly diffused light. (Think of being outside on a foggy day, when you can't tell where the sun is, and everything is evenly illuminated and shadowless.) This is difficult to achieve with a camera's built-in flash. It's also difficult to achieve with just one flash. For the work you've described--studio shots of insects from a museum collection, consider using two flashes, both positioned well-off camera. With a pair of off-camera flashes, there are two broadly-useful approaches that work well. One is based on diffusion, the other on reflection--rather opposite things.

For the diffusion approach, place a ring of diffusion material (tissue paper, two sheets of tracing paper, one sheet of printer paper, or purchased diffusion material) close to the insect, and illuminate this diffuser as evenly as possible with a pair of flashes placed relatively far from the diffuser. The goal here is to make as much as possible of the diffuser glow evenly with light.

For the reflection approach--possibly easier than diffusion--aim your pair of flashes away from the insect, and bounce them off the inside of a white box placed over and around both the insect and flashes. A polystyrene cooler works well as such a box. If you go this route, place something between the flash and insect so that no direct light from the flash can hit the insect--you want only light that has reflected off the inside of the white box.

There are good posts describing each of these methods. If you have questions, ask--and one of us will search for these posts.

Cheers,

--Chris S.

rjlittlefield
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Post by rjlittlefield »

clarnibass wrote:I also read in another thread that using both pmax and dmap and masking different parts is sometimes the best option. I haven't had to resort to this with what I did before, but dmap does have a lot less of the outer halo.
Just to reinforce the idea...

Yes, for many subjects combining DMap and PMax is definitely the path to best possible results.

Quoting from the FAQs page on the Zerene Stacker website:
What is the difference between PMax and DMap?

PMax is a “pyramid” method. It is very good at finding and preserving detail even in low contrast or slightly blurred areas. It's also very good at handling overlapping structures like mats of hair and crisscrossing bristles, nicely avoiding the loss-of-detail halos typical of other stacking programs. But PMax tends to increase noise and contrast, it can alter colors somewhat, and it's liable to produce fuzzy “inversion halos” around strongly contrasting objects.

DMap is a “depth map” method. It does a better job keeping the original smoothness and colors, but it's not as good at finding and preserving detail.

The two methods complement each other. Some types of subjects look good when they are processed automatically by PMax, but not by DMap. Other subjects are just the opposite. For particularly challenging subjects like bugs and flowers shot through microscope objectives, neither method is ideal by itself. In that case the best results are obtained by using human judgment and the retouching tool to combine the best aspects of both algorithms.

For further discussion of these issues, see “DMap versus PMax” on the Zerene Stacker: How To Use It page.
The cleanest margins are often obtained by using DMap and adjusting the contrast selection threshold so that all of the unfocused background gets masked ("black in preview"), except for a narrow band right next to the subject. The number associated with the slider bar is just the percent of pixels that are masked. With a small subject surrounded by lots of background, the best choice can end up producing quite a large number, approaching 100 percent.

Sometimes it is necessary to combine PMax and DMap even on the margins. For example with a bristly bug, the margin may consist of a mat of bristles, with bristles at significantly different depths. In this case a good approach is to use DMap to make the cleanest margin that it can, then retouch from PMax to improve the bristles.

For more information, see https://zerenesystems.com/cms/stacker/docs/howtouseit and the video tutorials on retouching that are linked on the main Tutorials index page.

--Rik

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