[FrancisK7]

Interesting article. f/36, wowza!

Since I'll be shooting on a rail with automated increment I could shoot wide open at f/2.8 for all I care.

I have always wanted to own Zeiss glass. Most of them have aperture rings. It would be splendid to have one for macro work! Something like the 21mm.

[Finn]

I want to hear more about the project...zooplankton in their natural habitat?

[FrancisK7]

Short story: I was diagnosed with ulcerative colitis last year. Standard treatments weren't working, I was in pain and had to wait for test results before starting new more cutting edge treatments. My doctor said the literature on medical cannabis to treat inflammatory bowel diseases was very convincing and that I should try it. I did, and it changed everything. I eventually got accepted in the MMAR (Medical Marijuana Access Registry) program, which is administered by the federal government under the purview of Health Canada. You can either buy your medicine from them directly, or grow it yourself. So I got what I needed to grow it in a safe place I am renting (just two plants to start, even though my exemption allows for up to 15 plants). The other day I stopped by the McGill botany campus to meet with a graduate student so I could ask a few questions about the scientific literature I had found in my research. (I'm a McGill student too). That grad student is working on her phD and requires microphotography work in the lab. So now she is helping me with my project, and I am helping out with hers. It's an exchange of professional service between two academics if you will. I wouldn't be surprised if she'd like a little bonus at harvest too

I will be photographing both her subjects (no zooplankton that I know of, but I would say yes instantly) and mine. I will need at least 8x magnification to photograph the trichromes that erupt out of the plant in late stage flowering.

[baro-nite]

I will be photographing both her subjects (no zooplankton that I know of, but I would say yes instantly) and mine. I will need at least 8x magnification to photograph the trichromes that erupt out of the plant in late stage flowering.

Fascinating -- thanks for sharing the story. I just acquired a bellows unit and will have to try some experiments around 8:1 and see what I get.

[baro-nite]

So, here's my first 8:1 test. SMC Pentax 1:2.8 30mm reversed on about 200mm of extension, lens set to f/4. By the crude measure of photographing a mm scale I confirmed somewhere around 8:1, probably a little more.



It's a feather (a small one). 23 image stack. Not enough; I was moving the camera on the bellows rail and the adjustment isn't fine enough for this kind of magnification, so there are some hazy areas.

100% crop: [edit: forgot that Zerene Stacker asked permission to resize to 75% before stacking, so this is a 100% crop from 75% of original size]



I chose this lens because of its relatively short focal length, allowing me to get to 8:1, and also because it is sharp at f/4. The 35 Limited would probably be sharper, though, if you worked out a reliable way to stop the lens down the desired amount (shouldn't actually be too hard).

[FrancisK7]

This is handheld?

[baro-nite]

This is handheld?

No, with a Pentax Bellows A on a tripod. Can't imagine trying this handheld, although I know it's possible.

[FrancisK7]

Well it will definitely show the details I need, but I hope that a DA*300 and a Zeiss 35mm will offer less diffraction than this, and a lot more sharpness (suppose a 60+ shots stack)

[baro-nite]

Well it will definitely show the details I need, but I hope that a DA*300 and a Zeiss 35mm will offer less diffraction than this, and a lot more sharpness (suppose a 60+ shots stack)

Unless the combination of those optics works out to less than f/4 (it might; I wouldn't know), you'll have the same degree of diffraction. This is why I was suggesting microscope objectives -- you might be able to find something faster, optimized for the particular magnification you need.

[FrancisK7]

I checked out the flickr page you referenced, but it doesn't look like any of these objectives are easy to find.

[baro-nite]

Did you follow this link from that flickr page:

Nikon 10x Microscope objective comparison | Flickr - Photo Sharing!

A quick eBay search turned many copies of both, and this is right in the magnification range you want. This is all very new to me so I don't know what is going to work best for you, but 8x magnification on an f/4 lens just sounds like trouble to me -- as good as the DA* 300 is, it improves on stopping down at least a little, which you can hardly afford to do at those magnifications.

[FrancisK7]

Oups, hadn't seen that one! Back to reading!

[audiobomber]

as good as the DA* 300 is, it improves on stopping down at least a little, which you can hardly afford to do at those magnifications.

I still think this is viable. Lots of people use the DA 55-300 with a Raynox 250 diopter and get good results. The DA*300 reaches max sharpness at f5.6, and is a lot sharper than a 55-300.

Maybe someone in the Macro Photography Group could speak with greater authority on shooting extreme macros.
Macro Photography - PentaxForums.com

[FrancisK7]

Well Dan, even if it doesn't work, it's not like the DA*300 is a bad lens, so it won't be a purchase I would regret anyway!

[Nass]

Forget about reversing the 35 onto the 300, it'll be rubbish. You'll always be diffraction limited. The thing is, at 8:1 macro you're going to get diffraction limitation with just about any combo of reversed lens... Remember, effective aperture is fstop*(mag+1). So f/8 at 8:1 is actually f/72, hopelessly diffraction limited. This is why we use microscope objectives at these sort of magnifications as they give you the best f/stop, and the Nikon infinites have been found to be especially good. For 8:1 I'd use my Nikon CFI Plan 10x/0.25NA 10.5mmWD on a 150-200mm tube lens or on a Raynox at infinity... but 10.5mm isn't exactly a huge working distance.

Objectives will get you the highest IQ by miles but you're looking at small working distances. If you want a longer working distance you might need to stretch to a Mitutuyo 10x infinite LWD (stands for "long working distance"), but they're not cheap... The longer the WD the higher the price basically, and in the infinite objective game nikon and mittys are really the only 2 major players in the game. Because they don't rely on eyepiece correction, so you can use them with a non-corrected tube as well.

Hope this helps a bit