Forensic Macro Photography

[agriffiths]

Hi everyone,

I'm after a little advice on equipment setup for gathering infrared images of soot on various surfaces at fire sites.

We are using a 12Mp Fujifilm S3PRo (nikon mount) with an infrared sensor and need to purchase a macro lens and ring flash to pick up as much surface detail as possible. So I am thinking of a macro lens with a ring flash and perhaps a distance bar / stand-of pillar to standardise the distance involved.

My first question to you macro boffins out there is what would be the best macro lens to use for this purpose?

Secondly, which ring flash would fit this lens and can adjustable standoffs be purchased or should I just fabricate one myself?

I'd be happy for any advice .

Cheers,
Griffo.

[moz]

can adjustable standoffs be purchased or should I just fabricate one myself?

I would be tempted to DIY if you have access to any metal fabrication skills just because you're likely to damage it from time to time and if you make it yourself it's easy enough to make the poking part replaceable. It should also be easy enough to make - I'm thinking a slightly bent or twisted strip that bolts to the tripod mount and is threaded to take a bolt that clamps the sliding standoff bar. Make the latter our of an old TV aerial or similar aluminium and it'll be pretty lightweight as well as easy to wipe off if you disturb some soot with it.

[ATJ]

Griffo,

There are a number of macro lenses to choose from and you'd need to consider how close you can get to the subject (or how far you can get away) and how large the subject is. A 60mm would be great in tight areas with larger subjects. A 105mm or even 180mm would be perfect for smaller subjects that you can't get close to. So, it is really going to depend on the fire sites as to which would be more suitable.

I've had a 60mm for over 10 years and I love it, but it is not good for small subjects a long way away.

What sort of detail are you trying to pick up? A ring flash will give fairly even lighting but you don't really get shadows. A rough surface, for example, would probably look less rough with a ring flash than with a single flash coming in from the side.

[the foto fanatic]

Griffo,
What sort of detail are you trying to pick up? A ring flash will give fairly even lighting but you don't really get shadows. A rough surface, for example, would probably look less rough with a ring flash than with a single flash coming in from the side.

The Nikon R1C1 system has a ring that mounts on the front of the lens. On the ring you place SB200 flashes (the kit comes with 2) and you can dial in the amount of flash required from each unit. The flashes are wirelessly controlled from a hot-shoe mounted controller. This system is very flexible for macro work.

[ATJ]

Griffo,
What sort of detail are you trying to pick up? A ring flash will give fairly even lighting but you don't really get shadows. A rough surface, for example, would probably look less rough with a ring flash than with a single flash coming in from the side.

The Nikon R1C1 system has a ring that mounts on the front of the lens. On the ring you place SB200 flashes (the kit comes with 2) and you can dial in the amount of flash required from each unit. The flashes are wirelessly controlled from a hot-shoe mounted controller. This system is very flexible for macro work.

Ah, so it is not a true ring flash. Sounds like a pretty good system.

[agriffiths]

Thanks for the fast replies!

Yes prefab's probably going to be the way to go here. I like Moz's idea of a bracket system bolted to the tripod mount. That shouldn't be too difficult to do.

The macro lens will be used primarily as a close up lens using an infrared sensor to identify carbon black spots on a burnt surface. This will allow us to come up with a carbon particle count, taking samples from various locations within a given site.

We just need samples the size of a 20c coin and will be able to place the camera right up close to the surface where necessary. For this reason, and based on suggestions provided by ATJ, I'm thinking that perhaps a 60mm may be the best solution?

What kind of sample sizes can be achieved with this lens?

Also, shadows etc are a non issue here so I'm still thinking that a ring flash will be the best way to go. Although the Nikon R1C1 system suggested by Cricketfan does sound like fun!

[ATJ]

Griffo,

Here's a quick and dirty of a 20c piece with my 60mm at its closest focusing distance. This is not cropped at all, just resized and a bit of USM.



Note that you can achieve exactly the same magnification with the 105mm, but you'd just have a greater working distance (which might help with lighting, etc.).

Here's a crop from the same image of the base of the '2'. Cropped, not resized and USM.

[agriffiths]

Ah, beautiful! Thanks for taking the time to post the images ATJ, that's precisely what we're after .

So is that the Nikon 60mm 2.8 lens? I'd hate to get the wrong one.

Also, would there be any compatability issues with the current range of ring flash units? I've been looking at the Sigma Ring Flash EM-140 DG Macro, which according to the Sigma website is supposedly designed for use with Nikon Macro lenses although there is no mention of the 60mm.

Thankfully the Fujifilm S3 has a Nikon mount with full support for TTL so compatability with the hot shoe should not be an issue.

[ATJ]

It is the Micro-Nikkor 60mm f/2.8D.

I've not used ring flashes so I don't know. You'd have to check what diameter/filter size they work with and compare to the lens specs.

[agriffiths]

Fantastic, thankyou .

It looks like I'll need an additional 62mm adaptor ring. Other than that this seems like an ideal setup for our application.

I'll post a few pics when we have it up an running.

[Matt. K]

I'd suggest the 105 macro but I would not recommend the ring flash for maximum surface texture detail. In order to gain the most surface detail you need to light the image with low cross lighting A ring flash cannot do this.

[agriffiths]

Thanks Matt. That could also be a possibilty in the event that this setup isn't up to the task.

However when you're onsite one needs to keep things simple. We are usually operating in unstable and often unfriendly environments where taking the time to set things up for each sample can be a challenge.

The macro ring with a fixed standoff allows for a simple way to stadardise all macro infrared samples and at this stage I'm all for simplification .

[Yi-P]

As Matt mentioned, a ring flash will kill all the details on the surface instead.

I would say a 2x SB flashes with a sync cord. Put them on the side and low angle to your subject surface, it reveals much more details than the single ring flash. A little DIY bracket if you're handy enough should solve the problem.