Aperature more important than ISO?

[Just Be]

I've been beating my head against a wall for awhile now. I've got it in my head that I have to always use the highest ISO (100 and rarely 200) to get the sharpest possible shot.

Which forces me many times to use an aperture that is not in the sweet spot of my lens (ex. 2.8 -4) The shot may be properly exposed but not sharp.

I'm now re-thinking my strategy. I'm going to keep it at a minimum of 5.0/5.6 and if I need a faster shutter speed I'll just raise the ISO.

Should I have known this all along? I've never seen it posted.

Fortunately the Xti does well at 400 and even 800. I have only used it in rare situations.

[grego]

They are all important (all vital for proper exposure), but aperture will control your depth of field which and make or break a picture.

Most lens will be at their sweet spot from f/5.6 to f/8. So higher ISO (closer to 1600) will be needed depending on your light and how much shutter speed you want.

[Just Be]

Thanks!

Then why do we constantly see in magazine articles that we MUST use ISO 100 for every shot. How do they do it? Even on sunny days obtaining a decent handheld shutter speed of 1/250 or more is hard to do at ISO 100 while trying to keep the aperature at 5.6-8.

[grego]

Thanks!

Then why do we constantly see in magazine articles that we MUST use ISO 100 for every shot. How do they do it? Even on sunny days obtaining a decent handheld shutter speed of 1/250 or more is hard to do at ISO 100 while trying to keep the aperature at 5.6-8.

If its not bright enough outside then you need to kick up the ISO if you want to stop down.

From ISO 100-400, on any new Canon models (20D/30D/XT/XTi, etc) you will get good quality. Your photos will be sharper if you are stopping down btw.

[ssim]

Grego has got it right here. You need to find a proper balance of ISO, shutter and aperture. The aperture is driven by what you are trying to accomplish from a depth of field perspective, ie. how much do you really want in focus.

I can't say as I have seen alot of people saying that it has to be done at the lowest possible ISO. I would have a hard time believing that anyone that knew what they were doing would advocate this as they know how hard it is. I can honestly say that my camera doesn't go below ISO 200 very often. Today's body are doing such a good job of noise management that you cannot tell the difference between a 100 and 200 ISO image unless you pixel peep at the pixel level. I don't have any qualms about moving my ISO up to 1000 or even higher at times. I have a 16X20 hanging on my wall that was shot at 1250 ISO and at normal viewing distances you wouldn't know it.

Don't believe everything that you read. There are alot of photographer bloggers out there that I have read alot of mis-information being provided by them. OTOH, there are alot of good ones giving good advice as well. You just have to weed out the bad from the good.

[Glenn NK]

I've been beating my head against a wall for awhile now. I've got it in my head that I have to always use the lowest ISO (100 and rarely 200) to get the sharpest possible shot.

Which forces me many times to use an aperature that is not in the sweet spot of my lens (ex. 2.8 -4) The shot may be properly exposed but not sharp.

I'm now re-thinking my strategy. I'm going to keep it at a minimum of 5.0/5.6 and if I need a faster shutter speed I'll just raise the ISO.

Should I have known this all along? I've never seen it posted.

Fortunately the Xti does well at 400 and even 800. I have only used it in rare situations.

You likely mean "have to always use the lowest ISO".

You wouldn't believe how many closeup flower shots I've taken at ISO 640 so I could use f/5.6 on a breezy day to prevent motion blur. In fact, I can't remember when I used 100 last.

Incidentally, I don't know which ISOs have the lowest blackframe noise for your camera, but for mine they are 160, 320, 640. There is a blackframe noise chart for the 30D on the "net", but I confirmed it with my own tests.

[2005GLI]

on my xt, i've noticed at iso400 it gives off alot of noise. Something i've just started to notice more and more.

[Just Be]

You likely mean "have to always use the lowest ISO".

Yes. Thanks. I corrected it. I meant the lowest.
Thanks everyone for your responses.

[howzitboy]

i usually set the iso till i get the shutter speed i want to use. id rather have a bit of grain then a shaky photo.

[crn3371]

Even though all 3 figure in to the exposure calculation, I usually give iso the lowest priority. For most shots, shutter speed and aperture are more important for capturing the shot as you pictured it. I usually adjust iso to give myself a faster shutter speed, or greater dof, as needed.

[ssim]

on my xt, i've noticed at iso400 it gives off alot of noise. Something i've just started to notice more and more.

Noise is subjective, what is alot to one person may be acceptable to another. However, if you nail your exposure your images should be fine coming out of the XT. I have used the XT at 400+ and made some very good prints from them. If you have to make alot of adjustments to the image to get the exposure right it will attract more noise.

[Roy Mathers]

You wouldn't believe how many closeup flower shots I've taken at ISO 640 so I could use f/5.6 on a breezy day to prevent motion blur. .

I don't think you quite meant that, did you? ie how does using f/5.6 prevent motion blur?;)

[simwells]

I never really use mine as low as 100, I don't notice any increase in noise up until around 400 at least. My minimums usually 200

[Glenn NK]

I don't think you quite meant that, did you? ie how does using f/5.6 prevent motion blur?;)


You are correct in pointing this out, and I should have worded it more carefully, as there are a number of less experienced members that would not have followed the logic. What I said was incorrect as it stands.

For a given ISO, scene, and lighting, opening up the aperture combined with a high ISO yields a higher shutter speed - which in turn counters motion blur.

[Glenn NK]

Noise is subjective, what is alot to one person may be acceptable to another. However, if you nail your exposure your images should be fine coming out of the XT. I have used the XT at 400+ and made some very good prints from them. If you have to make alot of adjustments to the image to get the exposure right it will attract more noise.

This point is all too often missed, and people (in their fear perhaps) try to make the lowest ISOs work for everything.

Proper exposure makes a world of a difference. For my flower shots, the main subject is usually "worked to the right" of the histogram and will be exposed more or less correctly (the flower is usually brighter than the background).

I don't claim to get the exposure "correct"; just more or less close.;)

[DAMphyne]

In the ancient world of film photography the lower the ISO(ASA) you could use, the finer the grain structure of the emulsion. With digital, you really don't have to worry so much about grain as noise. PP has lots of methods to reduce noise, and the new cameras have noise levels so low that they are hardly noticeable.
All three settings are important to getting the shot right.

[E-K]

Photography often involves some sort of compromise. Setting a maximum aperture setting that you will shoot at is no better than setting a minimum ISO. There are some situations were it will be better to use a larger aperture and some situations were you will be better served by a higher ISO. In some cases you make get lucky and the shot will allow for both ;).

e-k

[Roy Mathers]

You are correct in pointing this out, and I should have worded it more carefully, as there are a number of less experienced members that would not have followed the logic. .

A treacherous language is English!:lol:

[kevie]

Yeah my thinking on this has always been what ever will get you the shot do it. If it means setting your iso to the max then you do it. If it means setting aperture to completely open for the given lens(f2.8,f4,f5.6) then do it. Now if you have time to set a shot up and make it perfect then all the better. I typically will try and shoot in the lowest iso i can just because i dont want to have to take that extra step in Photoshop and have to reduce the noise. The less time i spend editing an image the more time i have to shoot. Yes if you want to stop motion/action your gonna need a higher shutter speed so if that means higher iso then do it if you can just open up the aperture i would do that first before bumping the iso.

[ItsMike]

I usually keep my ISO on my 30D around 200-800 when not using my flash, I for one Like Sharper pics and can deal with a little noise.. When I use my Flash I usually keep the ISO 100-200. I find that works best for me.. When I go to Baseball games at night The ISO is at least 1000 or better..

[ItsMike]

P.S. I use neat image for the noise removal and Find it to work real well.. Yea sometimes it softens the pic a little but then I would hit it with "Smart sharpen" in Photoshop and all is great.

[kevie]

Sometimes i get lucky and as an experiment i shot this at ISO 100 1/20 f/4 with my 17-40 L sorry its a link
http://farm2.static.flickr.com/1338/834553196_610ec1a876_o.jpg