Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-05-2014, 04:00 AM   #1
Veteran Member




Join Date: Mar 2009
Location: Australia
Photos: Gallery | Albums
Posts: 369
High speed, blurred image

I have encountered a strange phenomena photographing a piece of rotating machinery.

First image - 1/50sec f4.5, focal length 27mm, ISO 1600 internal flash. Stationary objects sharp, rotating equipment sharp enough.

Second image - 1/180sec f5.6, focal length 17mm, ISO200 external flash. Stationary objects sharp, rotating equipment motion blurred.

I can't post the images as they're work related unfortunately.

I shot a number of images characterized by the two images above, and the results were the same.

Why is the faster shutter speed giving motion burred images?

I also need to add the machinery is a constant speed device. It can only run at a fixed rpm.

11-05-2014, 04:04 AM   #2
Veteran Member
phoenixvision's Avatar

Join Date: Jun 2013
Photos: Gallery
Posts: 1,458
Try a much faster speed...180 is not that fast....you can push it to 1,000 or even 2,000....I dont understand why you would have higher iso for a slower speed...should be the other way around....raise the iso as you want to shoot faster, all else being equal......pump the iso up, open it up and shoot as fast as the light will allow until you can capture the clarity of motion you are looking for....
11-05-2014, 04:07 AM   #3
Veteran Member




Join Date: Mar 2009
Location: Australia
Photos: Gallery | Albums
Posts: 369
Original Poster
The shutter speed is limited to 1/180sec with my camera and flash. Why would 1/50sec give me a sharper image than 1/180?
11-05-2014, 04:24 AM   #4
Pentaxian
Fogel70's Avatar

Join Date: Sep 2009
Location: Stockholm, Sweden
Photos: Albums
Posts: 1,737
I would suspect that the external flash did not fire correctly for the second shot (or the flash might not be powerful enough for the setup).

The shutter speed used do not matter much when using flash (when flash contributing to most of the light in the image). The flash might fire for 1/10000s or faster.


Last edited by Fogel70; 11-05-2014 at 04:29 AM.
11-05-2014, 04:49 AM - 1 Like   #5
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
QuoteOriginally posted by jawsy Quote
I have encountered a strange phenomena photographing a piece of rotating machinery.

First image - 1/50sec f4.5, focal length 27mm, ISO 1600 internal flash. Stationary objects sharp, rotating equipment sharp enough.

Second image - 1/180sec f5.6, focal length 17mm, ISO200 external flash. Stationary objects sharp, rotating equipment motion blurred.

I can't post the images as they're work related unfortunately.

I shot a number of images characterized by the two images above, and the results were the same.

Why is the faster shutter speed giving motion burred images?

I also need to add the machinery is a constant speed device. It can only run at a fixed rpm.
Look at your settings

The first shot has high ISO, which means the flash is very low power for the exposure needed, flash power is carried by changing the flash duration, so in this shot, it is likely the duration could be as low as 20-30 micro seconds.

The second shot with a very low ISO, (all else being equal 4 stops lower) would require 4 stops mor light. So assuming 20 micro seconds for the first shot for flash duration the second shot would require 320 microseconds. Depending on shaft rotation, this might not be enough.

Can you also advise aperture for each shot so we can get the real impact.


The other possibility depending upon all settings is that one shot , the blurred one, had a much higher contribution of natural light, but that seems contrary to the settings you gave
11-05-2014, 05:33 AM   #6
Veteran Member
phoenixvision's Avatar

Join Date: Jun 2013
Photos: Gallery
Posts: 1,458
Maybe you dont need the flash at all try it without the flash and high iso....then you can adjust the speed...maybe you can use some natural light or other light source if it is too dark....
11-05-2014, 05:48 AM   #7
Veteran Member
chromo's Avatar

Join Date: Feb 2010
Location: North Coast NSW
Photos: Gallery | Albums
Posts: 563
QuoteOriginally posted by Lowell Goudge Quote
Look at your settings

The first shot has high ISO, which means the flash is very low power for the exposure needed, flash power is carried by changing the flash duration, so in this shot, it is likely the duration could be as low as 20-30 micro seconds.

The second shot with a very low ISO, (all else being equal 4 stops lower) would require 4 stops mor light. So assuming 20 micro seconds for the first shot for flash duration the second shot would require 320 microseconds. Depending on shaft rotation, this might not be enough.

Can you also advise aperture for each shot so we can get the real impact.


The other possibility depending upon all settings is that one shot , the blurred one, had a much higher contribution of natural light, but that seems contrary to the settings you gave
The aperture settings are quoted in the original post
11-05-2014, 06:25 AM - 1 Like   #8
Pentaxian




Join Date: Oct 2007
Location: France
Photos: Albums
Posts: 804
The decisive parameter is the flash duration, which is unknown here. We can suspect that the flash duration of the internal flash is much shorter than the external one.

11-05-2014, 07:33 AM   #9
Loyal Site Supporter




Join Date: Aug 2011
Photos: Albums
Posts: 1,725
Try turn SR off. I heard sometime the SR system doesn't work well around that speed, lower or higher speed does better.
If it is true, just choose a little slower speed.
I have never noticed this issue by myself, but might be your case.
11-05-2014, 08:22 AM   #10
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,814
QuoteOriginally posted by Lowell Goudge Quote
Look at your settings

The first shot has high ISO, which means the flash is very low power for the exposure needed, flash power is carried by changing the flash duration, so in this shot, it is likely the duration could be as low as 20-30 micro seconds.

The second shot with a very low ISO, (all else being equal 4 stops lower) would require 4 stops mor light. So assuming 20 micro seconds for the first shot for flash duration the second shot would require 320 microseconds. Depending on shaft rotation, this might not be enough.
I think this is at least part of the answer. Notice that the shutter speed difference is not nearly as great as the suggested flash speed difference. You may be able to see how much the flash contributes to each image's light - shadows or differences in color temperature.

The field of view difference is large. It seems like it should have caused the rotating parts to cover fewer pixels over time, so blurring is less likely. That confuses me a little. It's too bad we can't see the shots.
11-05-2014, 09:15 AM   #11
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,167
QuoteOriginally posted by Just1MoreDave Quote
I think this is at least part of the answer.
I concur. Flash duration is not as short as we might like for some subjects and the contribution of ambient light may be less than we think.


Steve
11-05-2014, 03:42 PM   #12
Veteran Member




Join Date: Mar 2009
Location: Australia
Photos: Gallery | Albums
Posts: 369
Original Poster
After taking all the comments in I took another set this morning. I think the key parameter as a few have suggested is the duration of the flash burst. Loading combinations of ISO and aperture to give a shorter programmed flash burst sharpen the image considerably in each case. If I had the time and inclination I could probably calculate the burst duration using the shaft speed and length of blur, but I'll have to leave that for another day.

Thanks for the prompt feedback.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, flash, image, images, length, machinery, motion, objects, pentax help, photography, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
High-speed sync Spodeworld Pentax K-30 & K-50 5 05-24-2013 06:33 PM
Blurred image on the KR Braga Pentax K-r 6 09-02-2011 05:01 PM
Example of AF, DR, high ISO and high shutter speed on K-5 benisona Pentax DSLR Discussion 17 11-30-2010 02:25 PM
HELP- when in auto mode why is my shutter speed at 1/80, BLURRED PICS!! Jori Troubleshooting and Beginner Help 16 11-30-2009 09:19 AM
Blurred pictures with slow-speed sync samiam Pentax DSLR Discussion 8 08-25-2009 11:43 AM



All times are GMT -7. The time now is 01:03 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top