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-   -   High Speed Subjects, Flash, and Shutter Speeds (http://www.railpictures.net/forums/showthread.php?t=18246)

Mgoldman 06-04-2019 08:05 AM

High Speed Subjects, Flash, and Shutter Speeds
 
Impressive shot, Loyd!

[photoid=699122]

Glad this made it off your hardrive and onto RP. Someone asked if I had seen Sean Hoyden's version of this shot, but because it was not on RP, it would likely take hours, if not days to find it. Months if it's on FB, less time if it's on FLCKR?

Anyway - caught my eye, obviously -

Thanks for being so kind as to not hide /omit the EXIF info.

This leads me to a question -

How does one freeze a subject going 110 mph using a shutter speed of 1/160th of a second? Perhaps, it does not matter how long the shutter is open, but instead, the duration of the flash - which typically, would be 1/200th or 1/250th, no?

I routinely shoot the NEC and have found it wise to keep my shutter speed at 1/640 minimum, often sacrificing ISO levels to shoot at 1/1250th or even faster depending on the angle and distance of the train.

I, too, managed the feat, but with one lone flash, I was only able to get a frozen ghost. I was after the blur as my intent was to photograph the station through the train, yet the flash managed to freeze the action of the highly reflective Acela livery. Never figured out how that was possible!

[photoid=432724]

Thoughts?

/Mitch

PS: That'd have been an SC for simply pulling it off. Surprised its not doing 110 mph to the front page, but it is the NEC on RP - in the Summertime.

RobJor 06-04-2019 12:35 PM

http://blog.sekonic.com/2017/05/11/d...lash-duration/

Basically not on/off with an early peak and rapid fall off

or

from our fav source

A full-power flash from a modern built-in or hot shoe mounted electronic flash has a typical duration of about 1ms, or a little less, so the minimum possible exposure time for even exposure across the sensor with a full-power flash is about 2.4ms + 1.0 ms = 3.4ms, corresponding to a shutter speed of about 1/290 s.
================
So 1/1000 th of a second or less duration

Bob

KevinM 06-04-2019 01:14 PM

As has been noted, flash durations are a lot shorter than flash sych speeds. The biggest issue I see with taking a photo like the one Lloyd posted is headlights. The flash will definitely freeze the train, but the ISO that's required unless you have a ton of flash power will likely get you some headlight blur if you're using a slow shutter, such as 1/250th.

Not being a strobist, I'm just guessing that the answers probably lie in high-speed synch and/or having beaucoup flash power, to keep the ISO down. Speedlights are probably not powerful enough.

bigbassloyd 06-04-2019 01:52 PM

It was a fun night, and nice to finally put the experiment to work.

We used 10 speedlights for the scene. After fine tuning the power levels to give a nice even result, we started shooting. Not one single flash was at full power for the record.

There's no issue whatsoever with freezing the train. The flash duration is around 1/800th of a second when you do the math at the power levels we used. Out of the 20-some trains we shot, none had the physical shell of the train blurred. We did learn quite a bit about the interaction with the lit number boards, and I adjusted my method to address it. Sean shot the Acelas, which do not have lit number boards. he was able to allow the train to come further into the scene successfully. So no problem shooting Acelas at 120-125mph with OCF.

The Sprinters and Marc units (and Cab Cars) have wonderfully bright LED number boards, so the closer they were to the camera the more apparent the blur was. At 110mph, the train traveled from six inches to nearly a foot forward during the 1/250th - 1/160th exposure. So getting as head on as possible, and firing when the nose was placed further back in the scene proved to be the ticket to tame the number boards.

Keeping the train rearward did allow a good view of the Bridge and the museum, which leaves no doubt as to where we shot.

I do wish that Canon allowed HSS control when using a transmitter in the hot shoe. Flash sync is 1/180th so I had to shoot 1/160th to prevent shutter curtain. Oh well. :)

Thanks for the interest!

Loyd L.

Dennis A. Livesey 06-11-2019 01:29 AM

Thanks for the clear explanation Loyd. I remember Sean wondering how this was all working. Now we all know.
Cool.

lakshman 07-03-2019 04:24 PM

Its a very nice picture... and the effort of setting up the flashes and firing them correctly needs a lot of skill. This is my first post on the forum, but i have been following many Rpnet photographers on Flickr mainly Micheal Berry (I am a huge fan of his work)..

Will try and learn a lot from all of you vetrans of railway photography here.

My Photo stream is here.. almost all railway pics taken around the Indian Subcontinent using railpictures.net as an inspiration.
https://www.flickr.com/photos/lakshmant/


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