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09-07-2014, 07:52 AM   #1
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Question about shutter speed

So I've seen this on a few other pictures but never asked. The photographer used:
1/320
7.1
ISO 400
250mm
It was a picture of a sunset. I asked him why he used 400 ISO instead of just using a slower shutter speed and 100 ISO. His reply was.
With the 1.5 crop factor the safety time is 1/(250x1.5)=1/375, so i was in AV and to safe f7.1 i use ISO 400 to go nearly 1/375. this for shots without tripod.

I get it that since he's at 250mm it's a lot easier to get camera shake but I've never read anything that 1.5 crop factor had anything to do with shutter speed. And I've only been shooting for four months but I feel like that shot could've been done with a slower shutter and 100 ISO. Especially with the in camera SR. He was using a k5 II btw. Since I've seen a few other pictures with similar setting (faster shutter speed and 400-800 ISO) I feel like I'm missing something or doing something wrong. Obviously if your subject is moving you need faster shutter but for something like a sunset, I don't get it.

---------- Post added 09-07-14 at 07:56 AM ----------

Also, he was in AV so I get why the settings ended up that way but why not just shoot manual at like 1/150 and ISO 100?

09-07-2014, 07:58 AM   #2
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He may be doing it to fully ensure that no camera shake would blur the details, knowing that the k-5II sensor would have good noise performance in the 400-800 ISO range. He just didn't want to risk anything to his hand shake - perhaps he has unstable hands and that's how he compensates.

In the past with 35mm cameras, the general guideline for acceptably sharp photos from handshake was 1/FL, and for guaranteed lack of handshake was 1/(5xFL). In the case of a crop sensor, some people use 1/(1.5xFL) for acceptably sharp due to how the crop sensor takes the smaller portion of the lens image (thus technically "magnifying" it).

While the k-5II's SR does allow up to 3 stops improvement, likely that photographer just didn't want to rely on it. If it came down to it, I myself would rely on the SR and probably shoot at 1/160s.
09-07-2014, 08:27 AM   #3
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The 1/focal length rule is just a "rule of thumb", a guide. There are other factors involved especially how practiced the photographer is, his technique, and the SR settings. Whether you use 1/FL or 1/1.5xFLor 1/2xFL just pick a number that works for you, and even then it is not hard & fast.

I would assume from the settings that the photographer was comfortable with 400 ISO on the k-5II, and wanted to keep his shutter speed up. Also when shooting a sunset the light is going to slowly diminish, so in Av setting things a little fast at first gives you some room in case the light decreases. Setting everything in manual is fine, except you will need to be changing your settings every few minutes.

But bottom line, there is no reason, just photographers choice, he likely could have used a number of different settings and got a good shot.
09-07-2014, 09:37 AM   #4
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QuoteOriginally posted by Another dyemention Quote
So I've seen this on a few other pictures but never asked. The photographer used:
1/320
7.1
ISO 400
250mm
It was a picture of a sunset. I asked him why he used 400 ISO instead of just using a slower shutter speed and 100 ISO. His reply was.
With the 1.5 crop factor the safety time is 1/(250x1.5)=1/375, so i was in AV and to safe f7.1 i use ISO 400 to go nearly 1/375. this for shots without tripod.

I get it that since he's at 250mm it's a lot easier to get camera shake but I've never read anything that 1.5 crop factor had anything to do with shutter speed. And I've only been shooting for four months but I feel like that shot could've been done with a slower shutter and 100 ISO. Especially with the in camera SR. He was using a k5 II btw. Since I've seen a few other pictures with similar setting (faster shutter speed and 400-800 ISO) I feel like I'm missing something or doing something wrong. Obviously if your subject is moving you need faster shutter but for something like a sunset, I don't get it.

---------- Post added 09-07-14 at 07:56 AM ----------

Also, he was in AV so I get why the settings ended up that way but why not just shoot manual at like 1/150 and ISO 100?
First off, are the pictures taken by this photographer exceptionally good that you have to wonder how he did it? I am not saying that he is not....
The reason I am wondering is why using the long focal length for a sunset picture. The choice of focal length also determines what setting to use in taking the picture. In the film days when there is no shake reduction features on camera or lens, the general rule of thumb for taking a 'sharp' picture hand-held without motion blur is to use a minimum shutter speed of 1/focal length. Of course, people with more steady hands can get away with slower speed. I would say for that particular instance with 250mm focal length, his choice of 1/320 would be appropriate (with camera or lens SR on).

The photographer could have used Av, Tv, P or TAv mode in this situation, but it comes down to which setting (shutter, aperture, ISO, focal length) gives the best result.

09-07-2014, 10:10 AM   #5
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Don't know about 250mm sunset picture.
But, I have used a 77mm and really needed a 100 or so for distance feature...
I could get closer in a boat :^$

As has been mentioned, the formula and rule of thumb is what it is and really varies by person and ability. Steady hands and etc.

I might just wonder about dynamic range using ISO 400...
I have used similar overall settings for a good result (mixing and matching ISO, shutter and aperture) but I started with ISO 80. And I had a tripod.

So, he had no tripod. Perhaps he had a variable aperture 70-300 lens and thinks it is sharp at 7.1 (I use 6.7 with mine). He made a generous allowance for shutter (my hands aren't steady, either) and looks like he used ISO to bring the brightness up in camera... Not out of the ordinary, looking at it this way.

I may have reduced ISO even with the same shutter and aperture to further protect highlights and raise shadows at home. How much to raise at home depends if it was a silhouette. How much to protect highlights depends if sun was in the frame. If the sun was in the frame, I really wouldn't want to clip any additional highlights by raising ISO in camera. And, if sun was in the frame, there be clipping. Who knows...
09-07-2014, 10:27 AM   #6
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Thanks everyone. Makes sense. I just usually shoot around 1/100 and 100 ISO so just didn't know if I was doing it wrong. And I mainly use a 50mm btw. So thanks again.
09-07-2014, 02:01 PM   #7
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Blur from moving the camera can ruin a shot. It's worth a compromise in other parts of the exposure to avoid that blur, because it's hard to fix when it's small, impossible to fix larger amounts. When you have to compromise something, make the compromise something that you can fix.

Raising the ISO isn't as big a problem. It might raise noise but software helps there unless it's really high. Dynamic range does decrease, but even with my K-7's fairly bad dynamic range at higher ISOs, 400 is an acceptable risk. A K-5 should be fine there.

The exact lens isn't mentioned so it's hard to say whether aperture could be opened. Depth of field can't be fixed later, and stopping down from wide open increases contrast. You don't usually need perfect sharpness for a sunset shot, though.
09-08-2014, 05:02 AM   #8
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the question of shutter speed and blur is somewhat related to size of print as well. the old rule of thumb from the film days of shooting 1/FL was for an 8x10 inch print, where a point of light had blur that resulted (when printed) in a 1/100th of an inch or less point on the print (something like depth of field as well. it was determined that this would be "acceptably sharp. Now fast forward to digital and crop sensor, this gets modified by the crop factor as well, so the hand holding shutter speed becomes 1 / (focal length x 1.5), but again for an 8 x 10 print.

for larger landscapes prints, shutter speed needs to be higher because the blur is magnified as you print larger. Sure shake reduction can help, but it is not always as good as a higher shutter speed. what i cant understand here is that if someone is that concerned about blur, why they arenot using a tripod

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