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01-27-2011, 01:45 AM   #1
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Decreasing EV to get faster shutter speed?

Hi, Guys,

A quick question: when I have the lens wide open and highest usable ISO set, is it a good way to get faster shutter speed by decreasing the EV? Another way of saying it is that is it always possible to get the correct exposure back by PP?

thanks a lot for any input!

01-27-2011, 02:31 AM   #2
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From my experience, with my K200D, this will give at best the same quality as using the next ISO value.. I haven't tried it with a more modern camera/sensor yet though.

Give it a go in controlled conditions, then you'll know.
01-27-2011, 03:22 AM   #3
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QuoteOriginally posted by shang Quote
Another way of saying it is that is it always possible to get the correct exposure back by PP?
Yes, it is but the more you have to push in post processing, the more noise you'll get.

The camera doesn't do anything else from a certain ISO level onwards. It is believed that this ISO level is 1600 for the K-5. After that, the camera just decreases the shutter speed and pushes in post.

ISO levels below this ISO threshold should give you a slight advantage as you are exploiting the additional amplification the camera applies.
01-27-2011, 03:22 AM   #4
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How possibly could ISO 51200 be not enough?

01-27-2011, 06:42 AM   #5
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QuoteOriginally posted by elho_cid Quote
How possibly could ISO 51200 be not enough?
QuoteQuote:
..when I have the lens wide open and highest usable ISO set,..
.......

btw, i do sometimes when taking my fast moving child indoor. or flash when inevitable.
01-27-2011, 07:58 AM   #6
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A correctly exposed image will be "better" than an underexposed image that is pushed.
01-27-2011, 08:50 AM   #7
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Try it and see. At least, you'll become aware of your comfort level with noise. Or you can always consider these images as surveillance photos. Give them a little green/monochrome tint for that sniperscope effect, eh?
01-27-2011, 09:35 AM   #8
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High ISO

Class A....I am confused about your post, isn't shooting at higher ISO one of the K-5's claim to fame. Shooting in manual the camera cannot adjust anything so should you avoid shooting higher than 1600 ? The reason I ask is that I am thinking of upgrading from the K-10 to the K-5 based to a large degree on the reports of the seemingly "too good to be true" ISO. Perhaps you were talking about jpeg shooting ?

01-27-2011, 10:25 AM   #9
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QuoteOriginally posted by shang Quote
Hi, Guys,

A quick question: when I have the lens wide open and highest usable ISO set, is it a good way to get faster shutter speed by decreasing the EV? Another way of saying it is that is it always possible to get the correct exposure back by PP?

thanks a lot for any input!
For the best photo quality (especially if you want to make large prints), you should test the ISO vs EV approach with RAW files and your preferred PP software:
  • If your PP has great noise reduction, high ISO is viable.
  • If your PP has great fill lighting, shadow recovery, etc. then low EV is viable.
Here's how I've been handling it on my K-r (but it's new to me and I still have much to learn): In dark settings I tried 1600 ISO first. If the shutter speed is still too low, then I experimented between higher ISO or lower EV. Both options have given me usable photos.

High ISO requires less PP work for me. Adjusting EV seems more finicky. In the future, I will generally stick to higher ISO and noise reduction until I find situations where that doesn't give acceptable photos.

If you are truly at the highest usable ISO (I'm not sure whether you mean higher ISO settings give you an unusable amount of noise that can't be fixed in PP, or that you've maxed out the camera's ISO setting), then your only real option for faster shutter speed is to decrease EV. You'll need to use both fill lighting plus noise reduction during PP.

Last edited by DeadJohn; 01-27-2011 at 10:31 AM.
01-27-2011, 12:37 PM   #10
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Push processing will always give you mediocre results when compared to a properly exposed image. With that said, yes you could do it. However, a time will come when that form of processing will eventually not be enough for you. I would really consider getting a better lens instead of trying to process it afterward. You will have more success and eventually a better image to work with.
01-27-2011, 01:06 PM   #11
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It really depends on the circumstances

I normally try to get the correct exposure - but there are times when underexposing with a faster shutter speed can make very good sense.

Here's an example on the K-x
- which I hasten to add I did "accidentally" -
original grossly under-exposed:

ISO5000, f/4, 1/13, 50-200 @ 50mm -
EXIF should be attached (caveat: PhotoBucket can drop metadata)
(the shutter speed should have been about 1/4 sec)

resultant shot after PP:

I had to bring up the brightness on this shot quite a bit.

Why did this work out for the better?

Well from my past experience although 1/4 sec is "doable" for me - the problem is that I get a lot of blurred shots due to subject movement - often the piano is nice and sharp - but the face is a blur - whereas 1/13 sec is more manageable - yes, there still will be blurred shots - but fewer - if one looks for peaks in movement.......

How did I do this "accidentally"? - what's wrong with the K-x metering?

Well it was underexposed because I was out of the metering range of the K-x -
ie: the light level was below the lowest spec'd level for the K-x meter!

The long boring bit -
I think I may have exceeded the K-x metering limit and the camera was trying to tell me by blinking all the relevant information - but so far I have not been able to find this in the manual to confirm my suspicions.

The reason why I suspect out of metering range is because the K-x manual specs say:

the K-x is spec'd to EV=1 (at ISO200, f/1.4) = EV=0 (@ ISO100, f/1.4) -

On the 50-200 f/4 kit zoom - f/4 max aperture

Calcs for f/4, 1/13, ISO5000 -
= ISO640, f/1.4, 1/13sec
= ISO100, f/1.4, 0.5 secs
This is EV (Exposure Value) = 2 (@ISO100)
this means I am managing to meter at about 1 stop below the K-x specs.
(allowing for -3 stops light loss at the sensor for using a f/4 instead of f/1.4 lens)

(BTW - 18-55 kit zoom manages this even better to about -2 2/3 stops below the spec limit. Please see posts #131, #132 in Kx in Use )
01-27-2011, 01:19 PM   #12
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QuoteOriginally posted by epqwerty Quote
Push processing will always give you mediocre results when compared to a properly exposed image.
That's not correct. The K-5 has such low noise that a pushed underexposed image will not at all look mediocre. I even do it with my K100D and get far better than "mediocre" results.

QuoteOriginally posted by SpecialK Quote
A correctly exposed image will be "better" than an underexposed image that is pushed.
It will have less noise but it won't always be better. I often deliberately underexpose to get a fighting chance at stopping motion. A pushed image with acceptable motion blur is far better than a correctly exposed image that shows all the undesired motion blur in all its glory with minimum noise. With judicious use of noise reduction, you can get the underexposed image to look just fine.

QuoteOriginally posted by DeadJohn Quote
  • If your PP has great noise reduction, high ISO is viable.
  • If your PP has great fill lighting, shadow recovery, etc. then low EV is viable.
Even in the second case you'll need noise reduction. Applying "fill lighting" or pushing the exposure will introduce the same (often a tad more) noise than having shot at a higher ISO setting.

QuoteOriginally posted by DeadJohn Quote
High ISO requires less PP work for me. Adjusting EV seems more finicky.
Pushing an underexposed image shouldn't be finicky as all you need to do is to bump up the EV. Anything else you need to do from there on, you'll have to do with a high ISO shot as well.

QuoteOriginally posted by jaytee Quote
Class A....I am confused about your post, isn't shooting at higher ISO one of the K-5's claim to fame.
Yes, but the K-5 is so good at higher ISO settings because the sensor contributes very little noise. You can exploit low sensor noise either by shooting at high ISO or by underexposing images and then pushing them in PP. In other words, a camera that excels at high-ISO will allow you to severely underexpose shots and still rescue them in PP and vice versa.

Some people maintain that the ISO setting on the camera is just a way to tell the auto modes (Av mode is an "auto mode" as well) of the camera to choose lower shutter speeds. That's not quite the case as within the non-extended higher ISO settings, the camera hardware actually uses a higher signal amplification. This helps to keep the proportion of the read-out noise low. If you have very little read-out noise (as the K-5) then this additional amplification is almost not necessary as it introduces noise itself. I think from ISO 1600 onwards, the K-5 doesn't raise the amplification anymore but just underexposes and pushes the the result.

QuoteOriginally posted by jaytee Quote
Shooting in manual the camera cannot adjust anything so should you avoid shooting higher than 1600 ?
I'm not sure I get your question. I'm confused about the "manual mode". But, in any event, you need not avoid shooting higher than ISO 1600. The thing is, you can, without loosing IQ.

QuoteOriginally posted by jaytee Quote
The reason I ask is that I am thinking of upgrading from the K-10 to the K-5 based to a large degree on the reports of the seemingly "too good to be true" ISO. Perhaps you were talking about jpeg shooting ?
I wasn't talking about JPG shooting. The K-5 will be a huge improvement over the K10D not only but certainly in great parts regarding the ability to push process images (be it for correcting underexposure or for lifting shadows) and for high ISO shooting.
01-27-2011, 06:30 PM   #13
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Well I might not ever understand all of what you kids are talking about, but it sounds like I'm going to see a big difference between the K-5 and K10. I love to shoot in the twilight and even on a tripod I often reach my limit. That is ...not wanting too slow of a shutter speed ...and not wanting to give up all DOF or to lose IQ with to high of an ISO. Sometimes you just want it all! In the old days I would push my tri-x to 800 and often the grain would be kind of cool looking. Still I'm going to try to wait a bit to buy the K-5 maybe the price will drop some and the stained sensors will be sorted out.
01-28-2011, 12:58 PM   #14
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0 light is 0 light, so underdeveloping (or shooting to the left) will only yield you smaller dynamic range (pending whether you go off the scale), or at best introduce lots of noise when you push the exposure in post.

- Properly expose your shots for the best quality.
- Use quality lenses that will give you an extra stop, or two, of light.
- Invest in a flash, these situations are what they are designed for.

c[_]
01-28-2011, 01:09 PM   #15
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QuoteOriginally posted by ll_coffee_lP Quote
0 light is 0 light, so underdeveloping (or shooting to the left) will only yield you smaller dynamic range (pending whether you go off the scale), or at best introduce lots of noise when you push the exposure in post.

- Properly expose your shots for the best quality.
- Use quality lenses that will give you an extra stop, or two, of light.
- Invest in a flash, these situations are what they are designed for.

c[_]
this is bang on but to simplify regardless of all the different ways of adjusting exposure in a camera there are only 3 true adjustments
aperture
Shutter Speed
ISO

so if your aperture is wide open (or as wide open as you want)
Your Shutter speed is as slow as yo want
then when you adjust EV it will increase the ISO. no other choice is left. there are only 3 things to set.
the fourth option of adding a Flash will add light allowing you to control the camera settings more to your taste.

Once you accept this then you make decisions based upon which is the least problematic adjustment for the effect. For me I will sacrifice for noise by raising ISO then clean up what I can in post, and if it can't be made to look natural then I will add contrasting noise like film grain and convert to b/w and eliminate colour noise/shift (this is in the extremes)

And owning a K5 Shang you shouldn't have to worry until you are well past Iso 3200 from all the samples I've seen
With film when I knew I would have low light issues I would always shoot b/w and pick a film appropriate to the subject
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