larkahn

I consider myself a novice. I have an old Coolpix P7800 and often take photos in a classroom where the lighting is so so. ISO can be pushed to 800 but photos get grainy after that. Widest aperture is f2.0. Because I don't want to be intrusive during a lecture, I usually use the zoom. I finally realized that the zoom will have an effect on the triangle. I've experimented with auto ISO or a maximum ISO of 800. Once zoomed, the widest aperture becomes smaller when shooting at aperture priority and the the auto ISO ends up higher than 800. If I want to shoot at ISO 800, I probably need to be more intrusive, move around the room more and not use the zoom, so that all things considered I can keep the ISO as low as possible and the shutter speed as fast as possible. while letting in as much light as possible with the wider aperture. It seems that the widest aperture is often talked about when discussing wide angle views and zooming in, fast lenses, etc., but the factor of zooming and focal length does not enter into basic discussions about the exposure triangle. Or am I mistaken with my impressions?

travisdeland Loc: deland, FL

the triangle is about exposure only-focal length can change a parameter, ie, aperture, but in itself, is not a direct component of exposure

Hans2675 Loc: Lancaster, Pennsylvania

It seems your issue is that the lens is not a "constant aperture." If the lens for example is F 3.5 - 5, the widest the aperture will be when you are completely zoomed in is 5. To get the same result you either have to up the ISO or lower your shutter speed.

Hans2675 Loc: Lancaster, Pennsylvania

It seems your issue is that the lens is not a "constant aperture." If the lens for example is F 3.5 - 5, the widest the aperture will be when you are completely zoomed in is 5. To get the same result you either have to up the ISO or lower your shutter speed. To help you could either use a tripod with a lower shutter speed, as long as your not photographing moving objects, or you can typically get away with quite a low shutter speed as long as you're not "shaky" hand held. Hope this helps, not sure if I completely understand your question.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

It seems that if you want to shoot at ISO 800 (or higher) it's time to get a newer camera that can do that.

larkahn

I think this probably answers the question. I need to do more reading (Peterson?). I guess I was just under the impression that the focal length changing the parameter of aperture didn't seem to be discussed. I get, though, what you're saying. Thanks.

f8lee Loc: New Mexico

Yes, you are a bit mistaken. You are conflating aperture with focal length, and while they are related the issue you describe has to do with the kind of multi-focal-length (i.e. - zoom) lens your camera has.

The exposure triangle, as it is called, relates only to proper exposure of the film or chip, and consists of just chip sensitivity (ISO), aperture and shutter speed. For a given ISO setting in a given lighting scenario (without augmenting the light using flash or floodlights, just to make this simpler) only some combinations of exposure time (shutter speed) and light passing through the lens (aperture) will provide the desired exposure. As the terminology of aperture and shutter speeds works with "halves and doubles" a 1 second exposure at f22 will expose the chip to the same number of photons as will a 1/500ths second exposure at f1.4. You can intuit that the latter will allow for "freezing" action while the former will likely cause blurry results unless the camera is on a tripod. Less intuitive is the depth of field increase that increases as the aperture is smaller (for a given focal length lens).

So that's the basic concept of exposure. What you are describing is, as has been mentioned, the downside of a zoom lens that is not constant aperture - but not all zooms are this way. Constant aperture zooms are more complex (and generally larger) than their variable-aperture counterparts; thus you generally see them referred to as "professional" lenses with high price tags. But point and shoot cameras like yours do not have this kind of lens, as that would make it 3 times larger and much more expensive.

The effects that zooming the lens makes on the final image, assuming the aperture is the same (et's say f5.6 for the thought experiment) is the apparent magnification which could lead to blurry results. That is, at the wide angle setting things seem far enough away that a shutter speed of, say, 1/60th second will "freeze" the motion of moving subjects. But zoom in to the maximum telephoto setting and the subject is now magnified in the scene, and to freeze that same action will require a faster shutter speed.

I hope that helps - you can search here for "exposure triangle" and see more detailed and graphical explanations of the ISO/shutter speed/aperture balancing act. But it sounds as though your camera simply is not up to the job you are trying to accomplish - not enough light in the room for a proper exposure at an ISO setting of 800 at the f5.6 maximum aperture of which your lens is capable.

larkahn

Yes, but I still want to try to work within the limits of what I have to develop a better understanding of the triangle. I'm overseas now, but actually do have a new-used Sony A6300 (1,500 shutter clicks) that I purchased, waiting for my return to the U.S. Can still use the current compact to learn more about the triangle, technique etc. I do realize that's more important than the equipment, even though the new camera will allow me to shoot at a higher ISO with less grain. Thanks for your thoughts.

bobfitz Loc: Kendall-Miami, Florida

Time to upgrade. There are countless cameras on the market at very reasonable prices that are head and shoulders above your Coolpix.

larkahn

Thanks. This definitely helps. Thanks for your explanation -- it definitely gives me a better understanding.

larkahn

Thanks. This definitely helps. Thanks for your explanation -- it definitely gives me a better understanding.

repleo Loc: Boston

There are zoom lenses with constant apertures, that is they can maintain there widest aperture throughout the zoom range. They tend to be better quality lenses and may be bigger and more expensive than their variable aperture counterparts.

Silverrails

If your Aperture is 5, and you want a lower ISO, the only other thing is Slow down the Shutter-speed, which would most like be best with a Tripod and a cable release, to avoid any blurry images from any problable camera motion.

speters Loc: Grangeville/Idaho

You're right of course, a lot of zooms do not feature constant apertures (that's why you have to pay a bit extra for those)!

Blenheim Orange Loc: Michigan

I think you are on the right track. "Work within the limits of what I have and develop a better understanding..."



Mike