Now, this seriously has me beaten, suggestions as to what is happening here please?

Discussion in 'B&W: Film, Paper, Chemistry' started by Ed Bray, Aug 27, 2012.

  1. Ed Bray

    Ed Bray Member

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    Okay, this is weird. I was processing another of my recent South Devon Railway images and I realised that the front of the locomotive is not as sharp as I would have expected.
    The image was shot on 5x7 film using a 210mm Apo-Symmar lens at 1/250th sec at f11 on HP5+ film, now I would have expected a sharper image than that recorded, but when I started working on the image in Photoshop CS5 I noticed that the number on the front of the engine was a distinct double image, but nowhere else showed a similar double image, this is not a blurred image such as would normally be expected from too slow a shutter speed. The film was processed in Pyrocat HD for 8 ins at 24 degrees C with a TF-3 alkaline fix. The image was scanned on my Epson V750 scanner with the better scanning film holder. I have checked the negative on a lightbox with an 8x lupe and it is definitely a double image on the negative!

    Full Image: focus was on the sleeper 8 up from the trackside marker as can be seen in the third image:

    [​IMG]
    SDR: 3205 GWR Collett 0-6-0 5x7 by Ed Bray, on Flickr

    Second image, the locomotive's number at 100% crop
    [​IMG]

    Third image: Focus point on 8th sleeper from tackside marker, sleeper marked 631.
    [​IMG]
     
  2. Steve Smith

    Steve Smith Subscriber

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    Does it look like that on the negative? I would suspect the scanner.

    EDIT:
    Don't answer that!

    It's quite a light locomotive (relatively!) so it is possible that it moved sideways slightly whilst the shutter was open.
    Although it hasn't quite reached the fishplate join in the tracks which could jolt it over a bit.


    Steve.
     
  3. jeffreyg

    jeffreyg Subscriber

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  4. Ed Bray

    Ed Bray Member

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    That's a possibility although I would have expected a blur between the 2 sets of numbers. Thanks Steve.


    I have another image from last week of that loco so will have a look at that under the lupe. Thanks Jeffrey.
     
  5. Steve Smith

    Steve Smith Subscriber

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    Looking at it again, there is nothing else around the smokebox door with the same amount of movement showing. This leads me to think that perhaps the number plate is not permanently fixed but is just dropped onto a couple of brackets and only that moved.


    Steve.
     
  6. batwister

    batwister Member

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    The front of something moving, if you're close to it, will always appear to be moving faster than the back. I can't remember the name of the phenomenon, I'll have a look...
     
  7. BMbikerider

    BMbikerider Member

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    It is very possible that because the front of the Locomotive is closest to the camera, the shutter speed used was not enough the completely get it sharp, or there was lateral movement in the loco because of a track defect which caused it to lurch slightly giving the double image.

    If it was lateral movement, the part of the image below the boiler would not have had so much movement, so would not show up in such a significant way.
     
  8. Marc Akemann

    Marc Akemann Subscriber

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    I'm with jeffreyg on this where the numbers may have been painted twice. The original numbers were off-center and perhaps they simply repainted numbers 3205 to center them on the number plate.

    If it's a matter of the number plate moving, then the whole number plate would be doubled, too. Not just the numbers.

    Just a guess...

    Marc
     
  9. batwister

    batwister Member

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    :blink: Goes to show how obsessed with details some photographers can be! The whole front of the train has motion blur! I can't find the name of this specific effect, really annoying. It's basically an effect of perspective, in the same way that a train approaching a station from a distance seems to be moving slowly - it then appears to be moving much faster as it gets closer to you and passes through the station. It can also happen in seascapes, with the waves crashing in front appearing blurred, while the distant waves or perhaps a boat, doesn't appear to have any motion blur. I'd really like to hear the scintific explanation, because I'm not sure why a perceptual effect translates as 'hard evidence' in a photograph.
     
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  10. summicron1

    summicron1 Subscriber

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    the trees behind the engine in that close-up of the numbers don't show motion blur while the numbers and other details of the engine do.

    Face it, the train was moving too fast. One would think 1/250 would be fast enough with the train coming at you but apparently it was moving across the field of view also and that movement was enough to cause blur.

    looks like you got another day of shooting trains ahead of you -- sucks, eh?
     
  11. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    Yes- the whole front of the locomotive is slightly blurred. I'd say the shutter speed was fast enough to keep the train en toto from blurring, but not fast enough to capture it as if it were standing still. Looks like the train gave a slight sideways lurch over an un-evenness in the tracks as it approached you.
     
  12. dpurdy

    dpurdy Member

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    It looks to me like the light box up above the numbers has a double image as well.
     
  13. batwister

    batwister Member

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    The tree isn't moving... I assume he's using a tripod, thus the background is still.
     
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  15. Ed Bray

    Ed Bray Member

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    I am so perplexed by this I am seriously considering visiting the main station area in the next couple of days to check it out.
     
  16. Ed Bray

    Ed Bray Member

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    Yes the camera was on a heavy tripod, I am sure the camera itself did not move.
     
  17. Marc Akemann

    Marc Akemann Subscriber

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    I agree there definitely is blur involved here but why are there two distinct sets of numbers? Blurry as they are.

    Marc
     
  18. Hatchetman

    Hatchetman Subscriber

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    I think it is motion blur. It's more obvious with the numbers because they show so much contrast. 35mm train shooters hope for minimum 1/500 if possible.
     
  19. batwister

    batwister Member

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    It really is quite simple, but nobody seems to be able to explain it adequately! I understand it in practice, but my physics is failing me. Another way of thinking about it is clouds - which generally move very fast indeed. On a windy day your foreground interest (a tree say) may show some motion blur from the wind, whereas the incredibly fast moving clouds above will retain detail. So it has to do with distance/time. The extreme example would be a plane flying at hundreds of miles an hour, yet it's much easier to freeze the motion of a plane flying at full speed several miles away than it is a slow plane coming in to land.

    An even more extreme example is the ISS, flying at 18,000 mph! With a telescope you may be able to photograph this much easier than a car passing in front of you at 30 mph.
     
  20. Hatchetman

    Hatchetman Subscriber

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    It is image speed across the film plane we are worried about.
     
  21. batwister

    batwister Member

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    If he'd stepped back and altered his perspective there would be no motion blur because the distance between him, the front of the train and middle of the train where there is full detail would be adequate. This is causing the confusion. I'd like to see some kind of equation that explains this distance/subject speed problem. It's almost like hyperfocal but for moving subjects.
     
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  22. nworth

    nworth Subscriber

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    Very curious - some places are sharp and others not. I notice some lack of sharpness in the foliage on the left as well, and I wonder if it might be the same thing. The number plate shows two distinct, sharp images, which pretty mush rules out motion blur. A reflection is one possibility. Another is that the film was not perfectly flat in the holder, and it "popped" during the exposure.
     
  23. batwister

    batwister Member

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    Please forget about the numbers, it's incidental. The whole front of the train is blurred. Please look at the highest res version.

    The shutter speed used is only adequate for the time it takes for the first carriage to exit the frame. Say 3 seconds.
    The front of the train would exit the frame in a fraction of that, so the shutter speed needs to be increased to freeze the front of the train - which is moving through the frame faster than the rest of it.

    The apparent differences in speed of parts of the train is an effect of the converging perspective or vanishing point.

    Thanks for mentioning that. Solved.
     
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  24. Ronald Moravec

    Ronald Moravec Member

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    Number plate was not secure.

    Film moved from humidity.

    Reflection off back of holder.

    Got it. faint image is what is recorded during the shutter close to full open time. The darker, more neg density, image is what is recorded during the full open part of the exposure which is longer. Leaf shutters have three components, close to open, open, then open to close. Depending on shutter speed, these three components are different percentages of the shutter speed. The dark areas have too little intensity to record during the opening and closing phases.

    Changed my mind, the faint image was during the closing phase when there was enough "pre-exposure" to partially excite the silver.
    '
     
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  25. DWThomas

    DWThomas Subscriber

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    Loose lens mount or lens board? Yeah, pretty far out, but thought I'd toss it in. I agree that the two sharp extremes of position, most obvious in the numbers, is a bit odd; I would expect more of a smear from just plain motion blur. Years ago I shot some rail stuff with hand held 4x5 and panned with the subject of interest; that appeared to work, but I doubt I ever examined the results this closely.
     
  26. Jim Jones

    Jim Jones Subscriber

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    Shutter bounce? More likely with focal plane shutters than the shutter in a lens, though.