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04-02-2011, 07:59 AM   #1
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Slow Shutter question

User Level: New to DSLR

This morning I was trying to experiment with my new K-r a slow shutter shot of traffic thus aiming to capture blurry for moving traffic on a road. So I tried different modes namely Tv mode and Manual mode separately.

I am not sure what I was doing wrong, I was using a Pentax 35mm f2.8 prime. When I set the shutter priority to be 1/8 or 1/10 something the aperture was stuck at its lowest aperture of f22 (to make the size to the smallest possible) and kept flickering. This shot was taken with sunlight at around 10am. It looked overexposed so i tried to AE compensation as down as possible and still it was a white dominated image and totally over exposed.

I did the same in manual mode and got another over exposed image. I am still trying to understand what I was missing to capture the blurry movement of traffic (not to freeze the movement).

Please advice.

04-02-2011, 08:11 AM   #2
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We can't see the shot to have a look. Are you saying the aperture on the lens was stuck? I'm a bit confused. If you set the exposure so that there was more light coming in than needed or the aperture was stuck open, then the shot will be over exposed.

Is this lens an a modern lens like an FA 35mm (auto exposure lens)?

If so, in shutter priority when you set a shutter speed that is too slow for a correct exposure, the lens can only close down so far and may not be able to limit the light enough coming in to achieve the correct exposure. So if you moved the shutter speed up to say 1/30th, the lens may now be able to close enough to get a correct exposure setting.

When you are at the limits of the lens aperture and the shutter speed is fixed (manual mode), adjusting a negative EV will not help. You're asking a lens that can close down to f22 to close down to f32. Clearly that can't happen.

Last edited by Peter Zack; 04-02-2011 at 08:19 AM.
04-02-2011, 08:12 AM   #3
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You were using TV, which means the shutter speed is the selected value at all times.
The aperture was already at its lowest value (smallest opening).

How do you reckon the camera can darken the image when it can't close the aperture further and it can't change the shutter speed?

What ISO value did you use?

If you need a few extra stops of light suppression, pop a neutral density or a polarizing filter.
If you don't own any of those, just use a faster shutter speed.
04-02-2011, 11:22 AM   #4
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Thanks Peter and ftpaddict. Yeah, I got your points but to get the proper exposure yes I know I need to increase the shutter speed but the shot I was trying to achieve was as mentioned by me earlier, want to capture the traffic movements (like water falls) - meaning blurry motion of the traffic therefore the shutter needs to be slow as possible. I am not sure if a shutter speed of 1/30 would do that? I was using the base ISO of 200 and can't go below that.
I am going to upload the picture here

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04-02-2011, 12:06 PM   #5
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I think that 1/8, 1/10, 1/30 is simply too fast for traffic.
I don't think it is really possible to capture big traffic blur at 10am, of course it depends on how much blur you want to capture, but if you look at typical pictures with traffic blur you will see that they were taken at night/twilight.

Plus, I see that you were in a car while taking the pic, you you were moving along with cars, I think that also wasn't helping.
04-02-2011, 02:08 PM   #6
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Consider evening/early morning for shooting to depict traffic motion blur.
During the day, you'll get too much light.
Unless you want to invest in a neutral density filter, it won't be a satisfying experience during the day.
04-02-2011, 04:43 PM   #7
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Your lens could not stop down any further and with the selected shutter speed, the image was overexposed.

04-02-2011, 07:29 PM   #8
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QuoteOriginally posted by SpecialK Quote
Your lens could not stop down any further and with the selected shutter speed, the image was overexposed.
That's exactly the issue. You may "want to" get the shot at 1/8th but the lens can't stop down enough to get the correct exposure. Ash is correct, either pick a darker time of day or get a ND filter.
04-02-2011, 11:00 PM   #9
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Another aspect of the blur is it appears you moving with traffic. Under perfect conditions if you were moving in exactly the same plane and same speed as the car in front of you the camera see the scene as if you are both still, while it would blur the road and background. Most of the blur in your photo isn't "motion blur" it is more camera shake. If you were standing on the side of the road and taking the photo of the cars going by the blur might be more pronounced.
04-03-2011, 02:22 AM   #10
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Thanks for all your contributions. So which means it is very normal that i wasn't able to achieve the effect and I was worried it is only me that I never knew how to take it.

Brydzo and ToGo, true what you say is right and the above was only an example (I also tried to take a shot on the road looking across the road while I wanted to see streaks of traffic passing across the screen. The one posted above was just a shot I took while keeping my brains working as to why I can;t get as I was driving back home but still I was trying to go at a slower pace as to other cars in my sides so hoping to get some motion blur on the side.

Learning: From all your suggestions the solution I conclude is either I should go after mid day or during sunset. Secondly I should try ND filter.

thanks all
04-03-2011, 04:01 AM   #11
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You don't need an ND filter if you just choose a darker time of day, such as dusk or dawn. Even night is OK if street lighting is reasonably balanced. You'd also need a tripod.
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