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TTL HSS flash for darkfield and oblique microscopy

 
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zzffnn



Joined: 22 May 2014
Posts: 1687
Location: Texas USA

PostPosted: Mon Dec 18, 2017 6:39 am    Post subject: TTL HSS flash for darkfield and oblique microscopy Reply with quote

Thank you for checking my thread.

I am considering buying a TTL high speed sync (HSS) flash for darkfield and oblique microscopy using Leitz Heine condenser (which is very light inefficient, though can switch between oblique and darkfield in one second).

Do you think either function is necessary?

I would guess HSS is not necessary, since my light source is just about enough for regular photo/video (and not more). So background light is not strong (low shutter speed of around 1/40 is usually used in my oblique light).

I do change between oblique and darkfield a lot quickly though. Would TTL help there? Or is it still not accurate enough, even though a tiny spot metering is used? It would be better than my manual flash, I assume?

Thank you again and happy holidays!
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mawyatt



Joined: 22 Aug 2013
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Location: Clearwater

PostPosted: Mon Dec 18, 2017 8:04 am    Post subject: Reply with quote

Don't think any of the TTL and HSS capabilities are going to work properly for your use, or most macro uses. Think most folks, myself included, use manual flash exposure.
For my studio use I mostly use the manual Adorama Studio 300 AC strobe and save my speed lights for outside work. I use lots of diffusion which eats the light as you mentioned, thus the need for the more powerful strobe.

Happy Holidays,

Mike
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zzffnn



Joined: 22 May 2014
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Location: Texas USA

PostPosted: Mon Dec 18, 2017 11:01 am    Post subject: Reply with quote

Thank you very much, Mike.

I forgot to mention that HSS is likely useful for my family portraits and sports under direct sun (which we have a lot in Texas). So it won't be wasted, if it is not necessary for microscopy.

I used manual flash before, with transmitted darkfield and oblique microscopy (viewing fast-moving pond protists). I could write down and remember each setting for each objective/illumination combo, though I am guessing TTL may make it easier for the 10 possible combinations I have? I do change between those 10 combinations quickly (5 objective lenses on turret, with 2 illumination methods).

I did find that sometimes camera metering can be off a bit, especially with darkfield. I may be able to compensate that difference (which seems relatively consistent), though I have not really tinkered it.

I have a micro four thirds camera (Oly E-M10 II) and am looking at Godox TT685 with its 2.4g transmitter.
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mawyatt



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PostPosted: Mon Dec 18, 2017 11:59 am    Post subject: Reply with quote

I would look at the Adorama equivalent brand, as they are rebranded Godox with US warranty. Many folks using these Adorama strobes and speed lights here is US with good reports. BTW the Adorama 300 studio strobe mentioned above is a rebranded Godox SK300II.

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Mike
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Pau
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Joined: 20 Jan 2010
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Location: Valencia, Spain

PostPosted: Tue Dec 19, 2017 4:03 pm    Post subject: Reply with quote

You don't want HSS for microscopy (nor high magnification macro). In fact if you set HSS you can shot with high shutter speeds just because the flash is firing continuously with short repeated pulses, in most cases actually providing longer exposure times than in normal mode when is the flash pulse itself what provides the exposure time, also the power output will be lower and the battery duration shorter.

TTL is more useful although in most cases M is to be recommended and specially for stacks.

With my Canon often I fire the flash in TTL and if right I use that power set in M mode. But, because the flash communicates with the camera, for me the main utility is to control the flash power from the camera, in fact from the computer with the camera tethered. I don't know up to what point it would apply to your Olympus.
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zzffnn



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PostPosted: Tue Dec 19, 2017 6:19 pm    Post subject: Reply with quote

Thank you very much, Pau. You have convinced me. I thought it over carefully and agree with you.

My light source is not even powerful enough to require HSS. Not to mention slower flash speed (I did not know that for sure, though I did know HSS is a continuous low power pulse).

Are you able to see the power level of TTL flash? I don't know how to find that (have not investigated carefully).

And yes, TTL is likely not accurate in microscopy, due to condenser filters and other manipulations that flash/camera cannot foresee. Likewise for macro, flash/camera cannot foresee diffusion over flash head.
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Pau
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PostPosted: Wed Dec 20, 2017 2:33 am    Post subject: Reply with quote

zzffnn wrote:

My light source is not even powerful enough to require HSS. Not to mention slower flash speed (I did not know that for sure, though I did know HSS is a continuous low power pulse).

http://www.photomacrography.net/forum/viewtopic.php?p=161563
At the first link you can see how HSS works and compare it with single pulse

Quote:
Are you able to see the power level of TTL flash? I don't know how to find that (have not investigated carefully).

With the camera tethered just after taking a picture I can see the exposure time in AV but not the automatic flash power, I usually just use M and shot few test pictures to calibrate it

Quote:
And yes, TTL is likely not accurate in microscopy, due to condenser filters and other manipulations that flash/camera cannot foresee. Likewise for macro, flash/camera cannot foresee diffusion over flash head.


In fact, as it measures the light effectively entering to the camera it is pretty accurate although more variable than M, of course if the image has big bright or dark areas you need to apply compensation like in normal photography. Again when used I find more convenient to just adjust power in M.
My Yongnuo in M still has more variation between frames that I would like but as flash is for speed to shot stacks I use continuous light.

With Canon DSLRs like my 7D another advantage of M over TTL is to avoid the mirror cycling...this can't apply to your Oly.

Edited to correct a mistake: E-TTL exposure is not shown.
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