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UltravioletPhotography

60/2.8D, 60/4.0 CO & Some Transmission Spectroscopy


Andrea B.

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We were discussing a paper which made use of the 60/2.8D AF Micro-Nikkor for some UV photographs. I was curious how well this older 60 could shoot UV. (There is a newer nano-coated 60/2/8G AFS Micro-Nikkor). The comparison lens is the Coastal Optics 60mm f/4.0 UV-Vis-IR APO, a dedicated UVIR lens.

 

These fotos are extracted Jpgs, straight out of the camera, resized for web viewing, no edits.

Lens aperture: f/8

ISO: 100

 

Visible References: Left 60/2.8D AF Micro-Nikkor, 1/800". Right 60/4.0 Coastal Optics, 1/320".

Each foto is 450 pixels wide, so if you expand your browser they will appear side-by-side.

The Coastal is wearing front extension tubes to block oblique rays. This increases its exposure time. No, apparently not. Sorry!!

taraxacumOfficinale_visSun_60microNikkAFD_20160419wf_46288small.jpgtaraxacumOfficinale_visSun_CO60_20160419wf_46301small.jpg

 

 

Ultraviolet: Left 60/2.8D AF Micro-Nikkor, 2". Right 60/4.0 Coastal Optics, 1.3"

It was very windy. Please do not judge the 60/2.8D AF harshly for this blur.

And so we have some differences in UV recording here requiring a look at the raw composities and raw histograms next. My experience tells me that the Micro-Nikkor is picking up UV mostly from the "right-side" of the BaaderU's UV range. There is some focus shift in the Micro-Nikkor. But my goal was just a check of whether it could record UV and so I did not attempt to assess the amount of focus shift.

taraxacumOfficinale_uvBaadSun_60microNikkAFD_20160419wf_46292small.jpgtaraxacumOfficinale_uvBaadSun_CO60_20160419wf_46306small.jpg

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UV Raw Composites from Raw Digger

Left 60/2.8D AF Micro-Nikkor.

Right 60/4.0 Coastal Optics.

 

taraxacumOfficinale_uvBaadSun_60microNikkAFD_20160419wf_46292rawComp.jpgtaraxacumOfficinale_uvBaadSun_CO60_20160419wf_46306rawComp.jpg

 

 

UV Raw Histograms from Raw Digger

 

60/2.8D AF Micro-Nikkor.

taraxacumOfficinale_uvBaadSun_60microNikkAFD_20160419wf_46292rawHisto.jpg

 

60/4.0 Coastal Optics.

taraxacumOfficinale_uvBaadSun_CO60_20160419wf_46306rawHisto.jpg

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Coastal 60/4.0 photo converted in Photo Ninja with a PN white balance preset made on Labsphere 99% white standard.

taraxacumOfficinale_uvBaadSun_CO60_20160419wf_46306pn2.jpg

 

 

Micro-Nikkor 60/2.8 photo converted in Photo Ninja with the same white balance as for the CO/60.

[Timber once made a lovely test which applied same WB across a variety of lenses. See, I remember!]

taraxacumOfficinale_uvBaadSun_60microNikkAFD_20160419wf_46292pn.jpg

 

 

Micro-Nikkor 60/2.8 photo converted in Photo Ninja with corrected white balance.

As a side note here I will observe that the "look" in this photo is very similar to what I would get when shooting with a Nichia 380nm UV-LED.

taraxacumOfficinale_uvBaadSun_60microNikkAFD_20160419wf_46292pn3.jpg

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And, so, can we make any conclusions here?

Well, one test on one flower does not a conclusion make.

 

For Taraxacum officinale, there certainly seems to be sufficient density of the UV-dark bullseye signature when the photo is made with the Micro-Nikkor.

Maybe the the Micro-Nikkor 60/2.8D AF has potential to be the "poor man's CO60", but more testing is needed. For one thing, I need to be convinced that the Micro-Nikkor can record enough UV under (about) 370nm.

 

If shooting a subject which has UV characteristics in the "left-half" of the BaaderU range, what might we get with the Micro-Nikkor? I wish I had some handy test subjects which displayed a variety of UV-reflectiveness in known bandwidths. Hmmmmm......a Sparticle board comes to mind. Would that be a good way to look at these two lenses for judging their comparative UV-capabilites?

 

*****

 

I also need to look at the construction of these lenses. Why is one flower larger than the other? :lol:

 

Here is an informal freebie: the Micro-Nikkor 60/2.8D AF is a nice sharp lens but the CO 60/4.0 eats it for lunch on the sharpness front.

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Andy Perrin
Andrea, can you help me out with interpreting the histograms? I've seen you post a lot of them, but I'm not sure what you are looking for in terms of UV photography. This seems like as good a place to ask as any.
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Having both AF 60/2.8 Micro and the Coastal 60/4 APO available to me, I was about to start looking for a D70 to make this very comparison. Then, I remembered I had given away my last specimen of a D70, or at least think so, as a search did not unearth any of these cameras.

 

Thanks for saving me the further troubles of a comparison, Andrea. Besides, too early for dandelions here anyway.

 

On a D70, I would expect the exposure difference to be bigger than the 1 EV reported here? In fact, "only" 1 EV is insanely good for a non-UV lens and I would like to have the experiment repeated with flash as the light source to verify this observation.

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Given that our UV photographs are subject to the false-colour phenomenon,

I wanted to know exactly what false-colours were being recorded

prior to the huge colour-shifts induced by application of white balance tools.

The raw composite photographs from Raw Digger show me that.

 

The general usefulness of the raw histograms from Raw Digger is that they show us

  • where and when colour channels get saturated (clipped),
  • something about the exposure range of our particular camera + lens combinations,
  • whether we are over or underexposing,
  • how much "headroom" we have available for pulling back highlights
  • and more stuff like that.

However, is there anything in particular that raw histograms tell us about the UV-ness of our gear? I'm not really sure. But given that UV photographs can often have extreme dynamic range - pure white to pure black - it is important to know how well you are capturing that. If you "expose for the highlights" or "expose for the shadows" in UV, results are often more extreme than they would be in Visible photography. When shooting UV landscape, for example, to see foliage at all, we often have to let in enough light to blow the sky totally. If we shoot to keep the sky under control, we can't see the trees. And so forth.

 

 

I've just made a note to myself to shoot the Labsphere standards with metering made respectively on the white, mid-grey and black standards to show everyone what shows up in the raw composities and raw histograms. I'll try to get this up soon.

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Andy Perrin
Ok, and yeah, I've only ever used them to check that nothing is getting clipped on the highlights or the shadows. Also, that comment made me think I should try a UV HDR pic or two.
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Hmmmm....let's see.

 

The CO60 has recorded in about 9.5 zones of EV.

The Micro-Nikkor has recorded in about 8 zones of EV.

 

So right there we learn something about the UV capability of the Micro-Nikkor. We are losing something in UV when we use it.

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Bjørn, that was not a fair comparison in terms of exposure time. By putting front extension tubes on the CO60, I have increased the exposure time haven't I ?? Because I'm blocking some of the oblique light??

 

Actually now I'm not sure about that. I just went out and made a few test shots and it doesn't seem to be so.

 

Ok......

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Both are 60mm Macro lenses and yet the FOV appears to differ by ~10%

 

Occam asks, "Are you certain both were set to f/8?"

 

I am wondering if both focus to INF?

 

added in edit,

 

Won't wider FOV gather more light?

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Both lenses report aperture correctly in EXIF.

Both focus to infinity.

 

And yes about fov.

 

So I need to run the test with the same fov for both lenses in order to compare exposure times.

I'm getting ready to look at the two lenses after dinner to see about this difference in fov.

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Internal focusing macro lenses change their actual focal length, the closer the focus the smaller the actual focal length is, affecting the FOV. Some 180mm macro lenses when focused to life-size magnification will have actual focal length closer to 120-130mm.
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The Nikkor reports *effective* aperture, the Coastal 60 does NOT. The only way to ensure the effective apertures are equal is setting the Coastal to the same value as the Nikkor, then (with fixed light and shutter speed) gradually open up the CO 60 until the histograms of the image become matched. Do this in visible light first, repeat in UV.

 

Alternatively, set the 60 Nikkor to infinity and f/2.8, then focus to the intended magnification and read out the effective aperture. This will indicate the change between nominal and effective aperture at that magnification.

 

There are close-focusing corrective systems on both lenses, thus their focal length changes with focusing and while both start at 60 mm set to infinity, they are not 60 mm at their close limit.

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I followed briefly up my own suggestions ....

 

Both lenses set to infinity and wide open (f/2.8 Nikkor, f/4 CO), shooting a scene in my back yard in broad daylight with the D3200 (internal Baader U): at least +1 EV advantage to the Coastal lens. Add to the 1 stop difference in lens speed and CO now leads by ~ 2EV or more. I just quickly read the histograms, no real quantitative measurement though.

 

Set the Micro 60 to f/2.8 and focus closer. At 1:2 it is down to f/4 (meaning 1 EV is 'lost'), at 1:1 it is f/5 effective (ie. 1.7 EV down).

 

For argument's sake, say Andrea photographed her dandelion at 1:2. Thus, as effective aperture is reported to be f/8, the nominal aperture would be f/5.6. The CO also is set to f/8 nominal and assuming its behaviour is similar to the Nikkor, the nominal value means actually an effective aperture at f/11. Thus the difference is at least 2 stops. The exposure data tells the Nikkor had another stop worth of additional shutter time. We end up with a rough estimate of the Micro 60 being around -3 EV relative to the CO 60, which is more or less what could be expected.

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Thanks!! You saved me some writing.

 

I never think about this stuff when making photos (obviously!). I just make the photos. Maybe I should think about it, but I don't.

 

What I would truly like to know, however, is what the Micro-Nikkor 60/2.8D AF bandwidth is in UV. It is passing some UV, yes. But from where?

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I have one NIkkor 60 2.8, not sure which model. bought new from BHphoto around 1998 (before I could afford a digital dSLR). I can try to do a rough test with my very old spectrophotometer to see if it transmits any UV.
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Zach, your 60 Micro is the same model as Andrea's (and mine). The newer AFS arrived on the scene just a couple of years ago so is mor recent and has nano-coating and suchlike stuff.

 

Andrea, in a way we are thrown back to the '60s when the Micro-Nikkor had a compensating aperture.

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This has been a very interesting and, for me educational, topic. Thank you all.

 

Curiosity about the 60mm Micro-Nikkor 2.8D led me to read some about it last night. I found a DXOMark review that gave an impressive result for T-stop of 2.9 for that lens. That translates roughly to ~93% transmission in the VIS for an f/2.8.

 

The transmission of the 60mm Coastal looks like it averages ~10% less than that through the VIS.

 

So as the spectrum descends into the UVA the Micro-Nikkor probably has about a 10% higher transmission than the Coastal before dropping into it's UV cut off, where ever that may be.

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Here is the verdict: yes, Nikkor 60mm 2.8D does have some UV transmission, about 40% compared to a EL-80? but not so bad if you have nothing else. Especially if on a liveview camera it will autofocus (perhaps not so well under UV).

 

Legend:

 

EL-80= our old friend nikkor EL 80, old version (with metal)

N60= Nikkor 60 mm 2.8AFD

N20= Nikkor 20-35mm 2.8D

Sony= Sony E3.5-5.6/18-55

 

Each lens was carefully aligned on the light path, and normalized at 700nm as 100% then manually adjusted wavelength and recorded % transmission.

Y axis = percent transmission, normalized at 700 nm (100%)

x axis = wavelength in nm.

 

post-41-0-44530400-1461195043.jpg

 

How did we "miss" this lens? haha.

 

I thought my tests so far made sense...but someone (Alex?) says it is not reliable (no integrator, for example). I do not move the lens once it is in the right position, so any changes in transmission if I change wavelength, I consider it due to change of tranmission, not to due diffraction etc.

 

Here we see that the Sony has almost nothing for UV transmission, but still a little bit between 380-400 nm.

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Thanks for the transmission test Zach. Yes, an integrating sphere should be used, but the test does give us some insight into the relative capability of those lenses.

 

There is enough between 370-400nm in many floral UV-signatures, for example, that the Micro-Nikkor 60/2.8 might be OK to use. The problem is that a researcher would not have a way to know in advance whether certain subjects, floral or non-floral, might have more to show in UV under the Micro-Nikkor's cutoff around 360nm. Something might reflect UV until 360nm and then begin to be UV-absorbing past that into the violet and blue areas.

 

And it seems odd to put a BaaderU with its 325 - 369 nm HWB range on a lens which only kicks in at 360nm. You can see from my examples above that after white balance, the dandelion photo was becoming more monochrome in its false colours (see blue example and ignore false colour).

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Here is the verdict: yes, Nikkor 60mm 2.8D does have some UV transmission, about 40% compared to a EL-80? but not so bad if you have nothing else. Especially if on a liveview camera it will autofocus (perhaps not so well under UV).

 

 

Zach, If your graph is correct, then the UV transmission of the N60 lens should be comparable to the Nikkor 18/4 or the Tamron 21mm/4.5.

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I thought my tests so far made sense...but someone (Alex?) says it is not reliable (no integrator, for example).

 

I had (!) to dig this out! It was not me complaining about your tests. It was someone else. I usually only complain about things directly related to optics and lens manufacturing.

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Bjørn: You cannot know the true existence of something you just did a brave attempt to block out.

 

This is such a Zen like comment. :)

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