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Nagasaki Jul 5, 2005 4:20 AM

eric s wrote:
Quote:

The larger aperture will give you more depth of field, which might make it easier to get the plane in focus.


A larger aperture (smaller F number) will give less depth of field and a faster shuuter speed. A small aperture (large F number) will give a greater depth of field but a slower shutter speed.

eric s Jul 5, 2005 11:01 AM

Thanks for the correction... I know that, but clearly the info got flipped somwhere in the process of writing that... let me go correct what I said so I won't confuse anyone in the future.

Eric

1020 Jul 6, 2005 8:52 AM

Eric...thank you so much for answering my questions. I think I have a better understanding. This is how I see it, tell me if I am right. If I am looking for better depth in my zoom shots I should choose a higher f number, which is a smaller aperature. This will slow my shutter speed and in turn my pictures will not be as clear, without a tripod. Now, both of these cameras (S2 and H1) have image stabilization, won't that work? AND...I understand for outdoor use you should use lower ISOfilm, which totally goes against what I always thought. I tought the higher # the better picture. Sooo...do I need to use different ISO film if I change the aperature to a higher number? I hope you understand what I am asking....I think I do!:?

geriatric Jul 6, 2005 9:27 AM

Hi

If you have microsoft excel spread sheet installed on your pcI will send you my full DOF chart.



Carrots Jul 6, 2005 9:59 AM

When taking photo's outside in daylight, the IS should be able to compensate for whatever the new shutterspeed at the smaller apperature would be. IS is no mirracle worker however. 12x zoom (432mm) indoors with reasonably dim lighting is a bit much for my shaky 25 year old hands and IS. For longer exposures (say 4s at night) with no zoom also leaves me with blurry results.

On the ISO question, I have never changed any settings on a film camera, but if it works the same as digital, then you would'nt necessarily need to change the ISO setting. On the S2's aperature priority mode, the camera automatically makes the shutterspeed longer when the apperature is smaller. It leaves the ISO as is.

The higher the ISO, the more noise will be on the image (on film I think itsgrain). But it will also be brighter.

Carrots Jul 6, 2005 10:18 AM

IS does helps in most cases. If you shoot outdoors in the day, IS should compensate for any reduction in shutter speed that the smaller aperature would cause. Although IS doesnt help my shaky 25 year old hands indoors (reasonably lit)with 12x zoom without a flash. Also without zoom, shutterspeeds of more than a second is also too much for me.

On your ISO question. I have never changed any settings on a film camera, but it should work the same as withdigital. On the S2s aperature priority mode, it only compensates for the smaller aperature by making the shutterspeed slower. It leaves the ISO unchanged.

Using a larger ISO makes the photo's brighter, but also increases the noise on digital, and I think the grain on film.

If Im wrong in anyway, sorry, and please correct me.

rjseeney Jul 6, 2005 10:37 AM

Higher iso's do not make a picture brighter. ISO refers to light sensitivity. Higher ISO's are more sensitive to light, allowing you to achieve faster shutter speeds at lower light levels. This is useful for indoor or low light shots where you don't want to lose flash, or where you want to freeze motion. The trade off is higher noise levels, which limits the quality of your prints and sharpness. You probably would not be able to print a decent 8x10 at iso's above 200 on most consumer level digicams.

eric s Jul 6, 2005 11:45 AM

1020
Glad to help. Part of why I come here so often is because I like helping people... it's in my nature. Thanks for showing your appreciation

I agree with rjseeney.

There is 1 "proper" exposure for a given scene that a camera will pick (I'm ignoring doing something special like emphasise a backlit scene when the camera would try to correct for that.)

But how that exposure is achieved is where the photographer and their skill (and intent) take over.

Let me give you a quick bit of background.

Say the proper exposure for a scene is:
f2 1/250 ISO100

All those settings are interrelated in the same why (nice of the inventors of this stuff, huh?) The rule is simple, it's all based around halfing or doubling. Changing 1 f-stop up (smaller aperture) halfs the shutter speed. Change 1 f-stop down (larger aperture) doubles the shutter speed. raise the iso (from 100 to 200) doubles the shutter speed. Teduce the ISO (from 100 to 50) halfs the shutter speed.

So all of these combinations produce the same exposure (But not the same picture!)
f2 1/125 ISO50
f2 1/250 ISO100 (more ISO = more shutter speed)
f2.8 1/125 ISO100 (smaller aperture = less shutter speed)
f2 1/500 ISO200 (more ISO = more shutter speed)
f2.8 1/250 ISO200 (smaller aperture + more ISO = same shutter)
f4 1/125 ISO200 (2x smaller aperture + some more ISO = slightly less shutter)
f4 1/250 ISO400 (2x smaller aperture + double the ISO = same shutter)

(if I've made a mistake, someone please correct me.)

But its the use of the side effects that help divide the snapshot shooter from the photographer. Maybe you want more DOF so you choose f4, maybe you want to isolate the subject from the background so you choose f2. Maybe you need to stop motion, so you pick the higher shutter speed, or maybe you want motion blur.

And you have to always weigh the noise that higher ISOs produce (which as said above obscures details and produces a less sharp image.)

As you said, if you increase the fstop (i.e. use a smaller aperture) you get a larger Depth Of Field, but a lower shutter speed. The problem will be how to use this when photographing planes. They are large objects (so larger DOF is good) but they are farther away (when flying.) If you go with a high shutter speed, you'll loose the motion blur, which can look bad. But panning with a plane to get the motion blur but keep them steady in the picture is hard. It takes practice.

My suggestion is to try taking the pictures with various settings and see what works for you. And don't expect perfection right away... shooting any moving object is not easy.

You are right, you can use higher ISOs to give you higher shutter speeds, but that raises the digital noise, which reduces overall sharpness. In other words, there is no free lunch!

Eric

1020 Jul 6, 2005 1:46 PM

Thank you for your response, but I am not the "plane shooter", I am shooting wildlife. Can you help me more with that?

eric s Jul 6, 2005 7:16 PM

Sorry.

With wildlife, you almost always want to stop the action. A blury animal almost always means you throw out the picture.

For big things, it gets tricker (the bears and moose you list.) They have such a large body you'll have trouble getting them entirely in focus. Luckly they also don't move a lot. You have two choices. Don't try to get them all in focus (you'd need a really big DOF) or try to do it. Just change your position so they are more wide then deep. DOF is infinitely wide, but the aperture controls how "deep" the DOF is. If you shoot the moose from the side, it will be easier to get it entirely in focus than from more straight on. Obviously, it's a better shot if the moose faces you, so that will make them a bit wider... but still skinny compared to more stright on.

Always, always, always get the eyes in focus. The shot won't work if the eyes are not in focus.

I'd suggest somewhere inbetween. Use a larger aperture to get some DOF... try shooting around f8 or so (that is where you'll optically be the best as well... probably, it's a safe generalization.) and then figure out which ISO value gets you a fast enough shutter speed without introducing too much noise. So take some test shots. See how much noise the different ISO values get you. BTW, this is one of the reasons that DSLRs are popular. They produce much cleaner images at higher ISOs that the P&S cameras (it has to do with the physical sensor size in the camera, but other things as well.) So while I can shoot at ISO400 and be generally happy with it (I prefer 200) you probably can't shoot at ISO400.

Another thing to look into is the programs neatimage or noise ninja. Both are noise reduction packages that you can train to learn what the noise "patter" is of your camera and then they will remove the noise without (in theory) removing detail from the image. They work well, and might save some images you otherwise wouldn't have shot. That might let you shoot at a slightly higher ISO.

Eric


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