Woophy - ISo speed rating, Exposure time and Apperture value.

Forum < Q & A < ISo speed rating, Exposure time and Apperture value.

Author	Message
Oyen Christiaan Member	# Posted: 2 May 12 19:51 Reply Something I can not understand. Is it possible that the shutter speed may have something to do with the ISO speed rating and aperture value. In the pictures I see that this is rather quite different. 1/15sec, 1/80sec, 1/125 or 1/800. Someone told me that the pictures were taken with a shutter speed of 1sec. And would also have used the zoom while recording. Can someone explain to me what this means. Thank you.
Oyen Christiaan Member	# Posted: 2 May 12 21:20 Reply Three photos taken with the same camera. (Pentax Kx) with the same program (creative programming; biased toward depth of field) 1; Iso speed 400, aperture value 7.1; 1/80sec exposure time. 2; Iso speed 400, aperture value 8.0; exposure time 1/400sec. 3; Iso speed 200, aperture value 8.0; exposure time 1/800sec. See my question above, please.
hardloperjan (Jan Landman) Member	# Posted: 2 May 12 21:38 Reply Its not simple to explain this in a view words Oyen may I give you a link to one of many (Dutch) sites, where some explanation is done ... http://wiskerke.home.xs4all.nl/artikelen/basis1.ht m There are many more photographic explaining Internet sites of cause, this is just one of them. Hope it will give you some answers Uiteraard willen we ook vertellen wat er bij jouw foto's gebeurd met de instellingen die de camera of jouzelf gekozen heeft Oyen, Hartelijke groeten, Jan Landman Papendrecht Nederland
A.Miguel Oliveira Member	# Posted: 3 May 12 00:53 Reply Hi, Oyen! First, let me tell you that I'm sorry that I haven't clearly understood your english in your first post. So, maybe I may be answering something that it's not your real question. Anyway, trying to guess your "problem", I'd say: a. Shutter speed really has "something" to do with ISO and aperture value: for the same amount of light to be caught in film/sensor (that means, for an almost similar picture) [NOTE: I say "almost" because the depth of field (focused subjects) will be different, not the exposure itself that will be equal] , if you push up ISO you will get a higher speed to get the "same" exposure; if you open up aperture you will also need a higher speed. In both situations because you are getting more light with the first step and compensate for it with the higher speed (which cuts light). b. From your second post (the example), I'd say that between the situation 2. and 3. you have different exposures (#3 has 4 times less light than #2): lowering ISO from 400 to 200 you'd need more light (double) to compensate, and so you should change from 1/400 s to 1/200. Changing to 1/800 you loose 2 "stops" that means 4 times less light. Pic number 3. will be darker than #2 if the source of light doesn't change, of course. c. Between the #1 and #2 situations, you have an almost 3 "stops" difference (darker is #2) or, we can say 8 times less light in #2 (because 2x2x2=! In all, #1, #2 and #3 lead all to different exposures, from a lighter pic in #1 to the darkest in #3 (compared to #1 this is 32X lighter or 5 "stops" less: 2x2x2x2x2=32)!!! If you need some extra explanation be free to ask Best regards from Porto, Miguel Oliveira
chill666 Member	# Posted: 3 May 12 22:03 Reply Jim Doty has a lot about expo and other useful stuff.. http://jimdoty.com/learn/exposure_lite/exposure_li te.html
Christiaan Oyen Member	# Posted: 14 May 12 19:14 Reply Thanks for your good explanation. I have a lot to read; http://wiskerke.home.xs4all.nl/artikelen/basis1.ht m and http://jimdoty.com/learn/exposure_lite/exposure_li te.html, and have learned a bit more about photography. thank you Christiaan.