Long closing time

[bslindgreen]

Hi


I have a Sony slt-a33 with the lens sal1820.




I Would really like to take a photo with a long closing time. But every time I try to the photo is all white... I can take a photo that looks ok with a closing time on 1,5 seconds. But I would really like to take a photo with a closing time on 30 seconds....


Can anybody help me with that??

 

[JoshuaSimPhotography]

Hmm, try to put your negatives down(-EV). And try a Neutral Density filter, that will really help

 

[Forkie]

If doing it during the day you need to find a way to reduce the light getting through the lens. Decreasing ISO, closing the aperture, using neutral density filters, etc.

 

[Solarflare]

Metering is a basic ability of all cameras.

Metering means the camera examines the light that is available, and chooses ISO, Aperture and Shutter Speed accordingly.

ISO describes how sensible your fotosensor is. The base value for ISO is typically 100, more rarely 200 or 400. At this point, the pictures will have the best quality. If light is bad, one might be forced to raise the ISO. This will, at some point, introduce noise into the picture. This happends almost immediately on compact cameras. High quality DSLRs might still produce nice results for ISO 3200, 6400, 12800 or even 25600 (I only heard of the Nikon D3s and D4 that they still operate nicely in these areas). ISO is usually always set to 100 (or 80 or 200 or 400, whatever the working point of the fotosensor is) and only raised if absolutely necessary.

Aperture is the opening of your lens. The larger the opening is, the more light gets in. Also, the smaller will be your depth of field, i.e. less items will be "in focus". This is an important effect for example for portraits, since having the background of the subject out of focus is a very desired effect. Also, closing the aperture a bit usually results in a bit more sharpness, especially also at the borders of the picture. However, soon an effect of diffraction kicks in and after that, resolution will be reduced again. Where exactly diffraction starts depends upon lens and fotosensor.

Shutter Speed of course is the time the picture takes to be taken.

This is called the trinity.

So if you just force your camera to have really long shutter times, you will overexpose the picture. Overexposure means the picture turns all white, since there was more light on the fotosensor than the fotosensor can handle and so it overflows.

As others already mentioned, the weapon of choice is a neutral density filter. In your case, a 10 stop one (ND1024) might be in order, since you want to have shutter speeds of 30s in bright daylight.

 

[pgriz]

If the intent is to use a long shutter speed in daylight, then the only way is to reduce the amount of light coming in by the use of a neutral density filter (8-10 stops) as posters already told you. This is assuming that you've already lowered your ISO to the lowest leve, used a high (ie, small) aperture, etc. Of course, using a ND filter that strong may make focusing very difficult, and may require you to do it manually.

 

[bslindgreen]

Thanks for all those great responds...

Can anyone recommend a good nd filter. I know that I've all ready got recommended the nd1024, but a I can see it only fits a 82mm lens (is that correct) as my lens is a 62 mm lens it wouldn't fit

 

[pgriz]

you mean, like this: http://www.amazon.co.uk/Multi-Coated-Neutral-Density-Filter/dp/B00485ZJJU?

 

[KmH]

You can get a step ring so you can use the 82 mm filter you already have with the 62 mm filter threads your lens has.
Adorama Step-Up Adapter Ring 62mm Lens to 82mm Filter Size