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Low shutter speed overexposed at max aperture should I get a new lens?

Toon49
Posted 15/06/2013 - 14:51 Link
Sorry not sure if this is the right place to post and sorry if this is a really obvious question but I'm just learning! Anyway I went to the beach today with the intention of taking photos of the sea with a slow shutter speed but its a fairly sunny day and every picture was massively overexposed at anything under 1/200 shutter speed. I was letting the aperture be automatic but also did it manually and the max it goes is f22 (ISo was 200).
I was using a Pentax k-x with the kit 18-55mm lens.
Was I doing anything wrong or would I need a lens with a higher aperture? If so what would you reccomend?
Thanks again in advance you're all very helpful!
CIBarker
Posted 15/06/2013 - 15:01 Link
Hello Jade a variable ND filter for your lens would have helped you out. Once you've got the lowest ISO the smallest aperture the only other thing to do to extend the exposure time is to reduce the light into the lens with a ND filter would do that without adjusting the colours you're trying to capture.
Best regards
Chris
gwing
Posted 15/06/2013 - 15:03 - Helpful Comment Link
If you are at the beach on a sunny day there will be *lots* of light so normal exposures will tend to be at high shutter speeds.

If you want to get the shutter speed as slow as possible choose the lowest ISO available on the camera and the smallest aperture (in your case f22) and then take the shot in AV mode or manual. There aren't really many lenses with apertures smaller than f22 so a different lens isn't the answer. Even doing all this the slowest possible shutter speed may not be as slow as you want, if so:

a) Do the same thing when there is less light (early morning, early evening, cloudy day).
b) Use something called an ND or Neutral Density filter to reduce the light. Essentially it is a piece of dark glass you screw onto the front of the lens.
c) Overexpose the shot a *little* then compensate for that in post processing. This isn't a good solution but if you can almost get a slow enough shutter speed but not quite it is worth a try.

The neutral density filter is the best option really. But you have to buy them and carry them and it is extra faff. They are available in different strengths so that you can choose how much light you cut out and hence how slow a shutter speed you can achieve.

Good luck,
Rob.
Edited by gwing: 15/06/2013 - 15:05
Toon49
Posted 15/06/2013 - 15:36 Link
Thanks guys really useful looks like a neutral density filter might be the best idea. I probably won't need it often its rarely sunny in the north east haha! Are they difficult to use or do you just literally stick it on and take the picture (obviously after adjusting aperture). Is there any you'd recommend or are they all the same and I just need one which will fit the lens? Thanks again
petrochemist
Posted 15/06/2013 - 15:39 Link
To expand on gwing's near complete answer

You'd have to have a really tiny aperture to get long exposures on a sunny day. For significant effect you need shutter speeds less than a second - 200 times less than you were getting. The only way to get close with aperture is to use a pinhole rather than a lens, but the image on APSC isn't sharp and most pinholes will still have too much light ~F/180 is typical.

IMHO a fairly strong ND filter (& tripod) will be needed unless you want o wait till the sun's gone down.
If you don't want to pay out for a ND filter (most strong ones are ~£100) it is possible to use welding glass (from ~£2) but you'll get a lot more colour change, and it takes a little DIY to mount it on your lens.
Mike
.
Pentax:K5ii, K7, K100D, DA18-55, DA10-17, DA55-300, DA50-200, F100-300, F50, DA35 AL, 4* M50, 2* M135, Helicoid extension, Tak 300 f4 (& 6 film bodies)
3rd Party: Bigmos (Sigma 150-500mm OS HSM),2* 28mm, 100mm macro, 28-200 zoom, 35-80 zoom, 80-200 zoom, 80-210 zoom, 300mm M42, 600 mirror, 1000-4000 scope, 50mm M42, enlarger lenses, Sony & micro 4/3 cameras with various PK mounts, Zenit E...
Far to many tele-converters, adapters, project parts & extension tubes etc.

.[size=11:].FlickrWPFPanoramio
Edited by petrochemist: 15/06/2013 - 15:41
CIBarker
Posted 15/06/2013 - 16:26 Link
Hello, 7dayshop do a variable ND filter 52mm to fit 18-55mm for £16.00.
Best regards
Chris
Toon49
Posted 15/06/2013 - 16:28 Link
Thanks been looking at and filters on eBay and a little confused would a cheap one like this for example be useless?
link
Toon49
Posted 15/06/2013 - 16:29 Link
CIBarker wrote:
Hello, 7dayshop do a variable ND filter 52mm to fit 18-55mm for £16.00.
Best regards
Chris

Thanks I'll take a look
Blythman
Posted 15/06/2013 - 16:56 Link
My father's day present for tomorrow

http://www.ebay.co.uk/itm/Haida-PRO-II-PROII-MC-Neutral-Density-Filter-ND-3-0-SL...

The cheapest good one, I think.

Before this I did it on the cheap with welding glass
Alan


PPG
Flickr
Gamka
Posted 15/06/2013 - 17:51 Link
Toon49 wrote:
Thanks been looking at and filters on eBay and a little confused would a cheap one like this for example be useless?
link

At a guess that is two polarising filters. When aligned they will only take out a small amount of light, but as the angle gets to 90 degrees it should go totally black.

I have used that method before but it can have odd effects on metering still so you might have to compensate up or down.

As for the seller - they are a business but don't show a VAT number which I would expect to see with the number of products they are selling and quantities with shipping from S Wales. And just a 2 month warranty!
JAK
Posted 15/06/2013 - 18:14 Link
Gamka wrote:


As for the seller - they are a business but don't show a VAT number which I would expect to see with the number of products they are selling and quantities with shipping from S Wales. And just a 2 month warranty!

Contact details show the to be in New Jersey, USA, so they wouldn't have UK VAT there. Odd though that the item is said to be in Wales.
As for customer service, Q&A shows,

Quote:
Q: Hello Emily and lily! Received my variable ND filter today and quickly realised I was meant to buy a 52mm not 58mm! Doh! I have no use for the 58mm, and was wondering if I could swap?
A: Hi, Thanks for your contact. So sorry we can only send the item you ordered. And couldn't exchange it. Thanks for your understanding in advance.

I've seen better!

JAK
John K
petrochemist
Posted 15/06/2013 - 19:09 Link
Gamka wrote:

At a guess that is two polarising filters. When aligned they will only take out a small amount of light, but as the angle gets to 90 degrees it should go totally black.

That's the way all variable ND filters work. Though the front one MUST be a linear polariser, and the second will normally be a circular polariser. With wide angle lenses they can give a darkened X especially noticeable in the skies.
Mike
.
Pentax:K5ii, K7, K100D, DA18-55, DA10-17, DA55-300, DA50-200, F100-300, F50, DA35 AL, 4* M50, 2* M135, Helicoid extension, Tak 300 f4 (& 6 film bodies)
3rd Party: Bigmos (Sigma 150-500mm OS HSM),2* 28mm, 100mm macro, 28-200 zoom, 35-80 zoom, 80-200 zoom, 80-210 zoom, 300mm M42, 600 mirror, 1000-4000 scope, 50mm M42, enlarger lenses, Sony & micro 4/3 cameras with various PK mounts, Zenit E...
Far to many tele-converters, adapters, project parts & extension tubes etc.

.[size=11:].FlickrWPFPanoramio
Gamka
Posted 15/06/2013 - 19:45 Link
JAK wrote:
Gamka wrote:


As for the seller - they are a business but don't show a VAT number which I would expect to see with the number of products they are selling and quantities with shipping from S Wales. And just a 2 month warranty!

Contact details show the to be in New Jersey, USA, so they wouldn't have UK VAT there. Odd though that the item is said to be in Wales.


I've seen better!

JAK[/quote]

Exactly, so they will have bulk shipped in the items and fulfilling from a UK centre - there has to be VAT at some point. Even if they sent the items to their fulfilment centre one at a time as they are a business VAT would be payable on the imports.

I wonder what HMRC would say about the operation.

My previous company was Canada registered, Head Office in the US and operated through the UK (and other locations). If we provided service to a UK/European company we had to charge VAT at 20%.
Mannesty
Posted 15/06/2013 - 20:50 Link
On sunny days it's good to remember the "sunny 16 rule" (Google it).

Basically it suggests that, in good sunlight and using an aperture of f16 (reasonably small), to get a correct exposure the shutter speed should be set to the reciprocal of the ISO speed.

Given that your lowest ISO is either 80, 100, or 200 depending on your camera, 1/80th, 1/100th, or 1/200th second shutter speed (or the nearest you can set it to) and an aperture of f16 will give you a correct exposure.

If your lens can be set to f22 or even f32, these are 1 and 2 stops slower than f16 and your shutter speed would need to be set to 1 or 2 stops slower to achieve a correct exposure.

Therefore if you are using either f22 or f32 on a sunny day, your slowest shutter speed will be 1/40th or 1/20th at ISO 80, 1/50th or 1/25th at ISO 100, and 1/100th or 1/50th at ISO 200.

From this you will see that the slowest shutter speed you could use on a sunny day and get a correct exposure at f32 and ISO 80, is 1/20th sec.

As others have written, a neutral density filter is your only sensible option to achieve slower/longer shutter speeds. I'd rule out the use of a pin hole as IQ suffers too much IMHO.

Hope that helps you to understand why your images were overexposed.
Peter E Smith - flickr Photostream
Edited by Mannesty: 15/06/2013 - 20:54
JAK
Posted 15/06/2013 - 21:09 Link
Gamka wrote:
Exactly, so they will have bulk shipped in the items and fulfilling from a UK centre - there has to be VAT at some point. Even if they sent the items to their fulfilment centre one at a time as they are a business VAT would be payable on the imports.

They could bee below the VAT threshold (£79,000) in which case it wouldn't apply.

John K
John K

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