27 replies to this topic

[dabateman]

I have been interested in the Olympus 30mm F3.5 Macro and thought it may be good for UV photography based on its lens design. So I finally rented one weeks ago and subsequently bought one. To give away the conclusions early, the Olympus 30mm can be used quite well for auto focus UV photography and has the advantage of being able to do in camera focus stacking on the Olympus EM1, EM5mk2 and EM1mk2 cameras.

All test shots were taken using a dandelion and two 365nm LED bulbs using the same fixed white balance.

The Sigma 30mm F2.8 lens is a excellent, with fastish aperture and good UV performance most likely down to at least 360nm. One clear thing I found from this comparison is that my Sigma 30mm actually has the field of view of a 28mm lens.

Sigma 30mm Art (smooth focus ring), at its minimum focus distance ISO 200 F4 with shutter speed of 1 second using 370bp15 filter:


The Olympus 30mm Macro at the same Sigma minimum focus distance, to match exposure I needed ISO 200, F4 with shutter speed of 1.6 seconds using 370bp15 filter. So only 2/3 to 1/2 a stop slower than the Sigma.


The Olympus 14-42mm R2 lens also seems to work for UV, it has slight better minimum focus distance than the Sigma. But its a slower lens, to match the field of view I needed F5.6. To match the exposure, settings were ISO 200, F5.6 with a shutter speed of 6 seconds using the 370bp15 filter. This is 1.5 stops slower than the Sigma 30mm and a full stop slower than the Olympus 30mm.


Here are comparison images using Baader Venus U filter to get an idea of the peak UV transmission. The Olympus 30mm is only 1/3 stop slower than the Sigma 30mm. The Olympus 14-42mm R2 lens is noticeably more blue than the Sigma, indicating that it does not transmit as much UV as the Sigma.

Sigma 30mm Art ISO 200, F4, Shutter 1/2 seconds, Baader Venus U:


Olympus 30mm Macro ISO 200, F4, Shutter 1/1.6 seconds, Baader Venus U:


Olympus 14-42mm R2 ISO 200, F5.6, Shutter 2 seconds, Baader Venus U:


However, what makes the Olympus 30mm Macro much more useful is it extremely close minimum focus distance. This allows it to be much closer to the subject that isn't moving and avoids the loss of reflected UV due to humidity and other factors in the air.

Here I have compared the Olympus 30mm with my Pentax UAT 85mm f4.5 lens with a similar flower head size on sensor shot. Since the Olympus can be physically closer to the subject it only looses 1/3 of a stop compared to the quatz lens. Making it very useful for UV focus stacking photography. However, the image is noticeably more blue than the UAT, I think I would pin its peak transmission at about 370nm.

UAT F8, ISO 200, 2 seconds, Baader Venus U:


Olympus 30mm Macro F8, ISO 200, 2.5 seconds, Baader Venus U:


So My guess is the peak transmissions would be roughly 360nm for the Sigma 30mm, about 370nm for the Olympus 30mm Macro and about 380nm for the 14-42mm R2 Olympus lens. These all say plus minus 20nm to indicate, I am only guessing. Although I don't see anything looking through a 340bp10 filter for any of these lenses. Using my tinny 350pb10 filter I could just see a faint outline of something in the dark with the Sigma 30mm, so 360nm for the Sigma 30mm may not be too far off.

The amount of UV transmission through the 30mm allows for focus stacking on a stock EM5 mk2 camera. So now knowing what I know, I would recommend as a first entry into UV photography to get an Olympus EM5mk2 camera with a 30mm Macro. And if you get a free 14-42mm R2 kit lens with the camera, as I did with the EM5mk2, you are still doing well for UV general UV photography.

Edited by dabateman, 11 June 2019 - 07:07.

[dabateman]

Here are some In camera focus stacking results using two 365nm LED lights

EM5mk2 Olympus 30mm Macro, ISO 800, F5.6, Shutter 10 seconds with Baader Venus U fitler:


EM1 Olympus 30mm Macro, ISO 800, F4, shutter speed 1/8 seconds with Baader Venus U filter:



The problem with the EM1 is that focus stacking is limited to 1/8 shutter speeds due to the electronic shutter limit. However, the EM5mk2 does not have this limit and can use electronic shutter up to 60 seconds.

My Stock EM5mk2 is 2 stops less sensitive at 390nm and 6 stops less UV sensitive at 370nm than my full spectrum converted EM1. Interestingly it also 8 stops less sensitive using a 720nm LP filter.

Edited by dabateman, 11 June 2019 - 07:49.

[JMC]

Interesting David. Always good to see an autofocus performer for UV. I find my little Canon 40mm pancake works quite well.

Do you have a StraightEdge II filter? Might works quite well with these lenses which don't transmit as deep into the UV.

Nice pictures by the way.

[dabateman]

Johnathan,

I don't have the Straight edge filters. But what I find works well for my indoor setting (I live in a dark cave mostly in the basement) is just a UG1 2mm or UG1 1mm filter. I can combine these with my none IR producing 365nm Lights to get a great response. These filters also work best with my 12.5mm stereo lens, as they are 52mm.

When I venture into the sunlight, I have a 25mm 390bp25, which is at least a stop faster than the Baader Venus filter. it actually has just over 70% transmission at 392nm, and almost no signal beyond 402nm. It also works very well with my stock EM5mk2, for hand held UV.

[JMC]

Ah right, thanks for explaining David. Yes, that 390bp25 will do a similar job then.

[Dmitry]

There is firmware hack for Olympus cameras to get focus stacking work on any MFT lens.

[Dmitry]

Have you tried Olympus FT lenses on FT-MFT adapter?
25mm/f2.8 pancake have simplest design 5 glass in 4 groups.
35mm/f3.5 macro have no cement - 6 glass in 6 groups

MFT Sigma 30mm/f2.8 have more complex design 7 glass in 5 groups.

[dabateman]

Dmitry,
I have not seen that hack. Can you PM it too me.
I have the Olympus 35mm f3.5 FT lens and it too is good for UV. But as far as I have tested no FT lens, even with MMF3 adapter works with either focus stacking or focus bracket.
I do not have the FT 25mm pancake.

[Dmitry]

Can you please add 35mm macro FT lens to this comparison?
Unfortunately hack does not allow to use FT lenses in focus stacking mode.

[dabateman]

Thank you for the link. I somehow missed that. I hope Abel can hack other odd limits, like the 1/8 electronic shutter limit. That is a big issue for me for UV photography and one of the reasons I purchased a Em5mk2. But it has a 8 second limit for high resolution mode. If it were 30 seconds, would be ok.

Yes I can try my 35mm f3.5 FT lens. I will have to find an other dandelion. They are now becoming rare. I may switch to a yellow cover as I think I still have some.

[Dmitry]

I think 8 sec limit because increased noise with longer shutter.

[Andy Perrin]

Huh, noise decreases with exposure because you average it out.

[Dmitry]

Another possible reason for the limitation is that the displacement of the sensor cannot be stable enough to maintain a precision of a shift of 0.5 pixels in the long term.

Anyway, I'm really interested in comparing lenses on the same body.

[dabateman]

Dmitry maybe correct on both accounts. Holding the sensor perfectly still with that fine a shift for long periods may generate internal heat and loss of presion. So maybe the 8 second limit used has a good safety margin to ensure crisp details and less noise due to heat.

However, the 1/8 electronic shutter limit in the Em1mk1 I think is just stupid. Since electronic shutter was released after the fact, via firmware. Olympus most likely wanted you to buy the Em5mk2. Well I did, but very cheap used. Stupid in that the sensor can handle longer exposure time, known by other cameras that use the same core Panasonic MN34230 sensor.

Dmitry, hopefully I will be able to test the 35mm Macro tomorrow. As a bonus I may test my Sigma 30mm f1.4 43rds lens as well as I just noticed it has 7 elements in 7 groups. So it may work, not sure until I test it.

[Dmitry]

I understand the perplexity about the 1/8 restriction and I understand the reason why the restriction should be removed.
You did not indicate which camera was used to take pictures in message #1, is it stock or converted body?

[Pedro J. Aphalo]

With the E-M1 (mk 1) and most recent firmware the Sigma MTF 30 mm f:2.8 can do focus bracketing without need of a hack. Focus bracketing also works with a Kenko 10 mm macro extension tube and the same objective. I agree, the max 1/8 s and no flash with focus stacking are important limitations. Thanks for sharing the comparison with the M.Zuiko 30 mm macro!

Edited by Pedro J. Aphalo, 12 June 2019 - 21:59.

[dabateman]

Pedro,
The Olympus firmware allows for just focus bracketing. The hack firmware allows for in camera automatic focus stacking with any micro four thirds lens. This includes the 10mm and 16mm extension tubes with the Sigma lens. I tested this today. So you are no longer limited to just pro lenses for incamera auto stacking.
It doesn't allow for stacking using either the MMF3 adapter or my cheap Chinese 43rds to m43rds adapter. Even with just the adapter and no lens. The focus section is grayed out.

Dmitry,
My post 1 is all with my full spectrum converted Em1 camera. I will post my updated images tonight. But the Olympus 30mm macro was better than both the 43rds lenses.

[Dmitry]

Oh, I see. Now everything is more clear to me.
I'm still thinking about what to do: repair my sigma 30 mm or get Olympus 30 mm.

Or convert any damaged MFT lens and install a Lomo T-43 lens instead of the original glass to get autofocus T-43

[dabateman]

Dmitry, if you could repair your Sigma 30mm, than that would be the cheapest option. Sending it to Sigma for repair may cost more than a Used one. The Olympus 30mm Macro is a good lens, but the used prices are more than the Sigma. So its a trade off.

I have only used one Sigma 30mm F2.8 art lens, but its quite good. I rented one Olympus 30mm Macro and bought a different one. The one I rented from Lens Rentals was sharper than the one I now own. But the one I purchased seems to transmit more UV, at about 1/3 of a stop more than the rented one. So it a trade off. The rented one was a little sharper than the Sigma 30mm. The Olympus 30mm that I now own, is a little softer than my Sigma 30mm.

[dabateman]

This is a new test adding some old Four thirds lenses. All tests were performed on my Olympus Full Spectrum converted EM1mk1. There are two 365nm light bulbs positioned on the flower subjects. In these images you can see the desk lamps positioned.

All these images were taken at the minimum focus distance of the four thirds Sigma 30mm f1.4 lens, which is about 40 cm. The white balance was set at 2500K for each to compare "blueness".

Four thirds Sigma 30mm F1.4 at ISO200 F4 and 3.2 seconds shutter speed using 370nm filter:


Four thirds Olympus 35mm F3.5 Macro at ISO 200 F4 and 1.6 seconds shutter speed using 370nm filter:


M34rds Sigma 30mm F2.8, at ISO 200 F4 and 1 second shutter speed using 370nm filter:


M34rds Olympus 30mm F3.5, at ISO 200 F4 and 1.3 second shutter speed using 370nm filter:



Four thirds Sigma 30mm F1.4 at ISO200 F4 and 1/2.5 seconds shutter speed using Baader Venus filter:


Four thirds Olympus 35mm F3.5 Macro at ISO 200 F4 and 1/1.6 seconds shutter speed using Baader Venus filter:


M34rds Sigma 30mm F2.8, at ISO 200 F4 and 1/3 second shutter speed using Baader Venus filter:


M34rds Olympus 30mm F3.5, at ISO 200 F4 and 1/2.5 second shutter speed using Baader Venus filter:



Close focus frames, however this time I wasn't so good at lining up the flower head. But you still get an Idea of the test:

Pentax UAT 85mm F4.5 lens with Baader Venus filter, at F8 ISO200 and 1 second shutter speed:



Four thirds Sigma 30mm F1.4 with 10mm extension tube at ISO200 F8 and 2.5 seconds shutter speed using Baader Venus filter:


Four thirds Olympus 35mm F3.5 Macro at ISO 200 F8 and 2 seconds shutter speed using Baader Venus filter:


M34rds Sigma 30mm F2.8 with 10mm extension tube, at ISO 200 F8 and 1 second shutter speed using Baader Venus filter:


M34rds Olympus 30mm F3.5, at ISO 200 F8 and 1.6 second shutter speed using Baader Venus filter:



All images are straight out of Camera Jpegs. The fast sigma is noticeably soft at F8 and much more blue than the other lenses. So it most likely is not transmitting as much UV as the other lenses. The Olympus 35mm Macro, is slower than the newer Olympus 30mm Macro, but may be transmitting just as much UV as the M43rds Sigma. As the image of the Olympus 30mm is slightly more blue.

So oddly the Newer lenses are better for UV transmission, must be a better coating. The older Sigma 30mm is actually a 30mm, equivalent to the Olympus 30mm field of view. My Newer Sigma 30mm f2.8 is actually a 28mm field of view as you can also see from these images.

After these tests I think at T₃₇₀ value would good to report for lenses. This would indicate the true exposure on sensor for the lens. This would be different than the UV range of a lens, which I now think the older 35mm having a slower T₃₇₀ value than the newer Olympus 30mm, but looks to transmit deeper into the UV spectrum.

UAT F4.5 is 5 elements in 5 groups but SiO2 and CaF2 Assume T₃₇₀ = 4.5
Sigma 43rds 30mm f1.4 is 7 elements in 7 groups (T₃₇₀ = 3.2)
Olympus 43rds 35mm f3.5 is 6 elements in 6 groups (T₃₇₀ = 5.6)
Sigma M43rds 30mm F2.8 is 7 elements in 5 groups (T₃₇₀ = 3.6) Winner, even with fewer groups So really don't know until you test.
Olympus M43rds 30mm f3.5 Macro is 7 elements in 6 groups (T₃₇₀ = 5)

Edited by dabateman, 14 June 2019 - 07:48.