Question about Cameras

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Image Properties shown....

1. What is Exposure Bias?
2. What is the actual distance between the subject with a property of 9.11 focal length?
3. What is the actual distance between the subject with a property of 4.6
focal length?
4. What is the Digital Zoom Ratio? i.e. 3072/3072
5. Is there anyway that a person who's Image Properties is 4.6 take their own picture and have the picture come out with good clarity, no movement showing, centered.
6. can they take 3 good pictures within 1 minute by using the timer?

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1: bias means voltage a neg or plus I assume the plus means more exposure.
2: focal length in feet ..if not using auto-focus
3: 4.6 feet
4: digital zoom is something I would never mess with but 3072/3072 sounds like a 3 megapixal square.
5: yes set the exposure to a fast shutter or bias in your case like - 3
6: why sure and quite a few pics in 1 minute with the right camera.

Posted on May 10, 2008

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I couldn't seem to blur my portrait backgrounds with the canon powershot a1200. can you help me with step by step instructions? does the a1200 have an AV mode at all? thanks

You're trying for what's called a narrow depth-of-field (DoF).

DoF is controlled by three factors: the aperture of the lens, distance to the subject, and the focal length of the lens. This has nothing to do with any particular design, it's simply physics.

The wider the aperture (smaller the f/number), the narrower the DoF. The A1200 does not have an Av mode which would let you control the aperture directly. However, it does have a Portrait mode, which is supposed to give you a wider aperture.

The closer you are to the subject, the narrower the DoF. This suggests that you get as close to the subject as practicable. However, in general you don't want to get too close for portraits as this tends to exaggerate certain facial features, like making noses look bigger.

The longer the focal length of the lens, the narrower the DoF. This suggests that you back away and zoom in. Yes, this conflicts with the previous paragraph.

Unfortunately, it's the actual focal length of the lens that matters here, not the "35mm equivalent" often quoted in the spces. The lens on the A1200 zooms from 5mm to 20mm. Landscape photographers like to use 24mm lenses on their 35mm cameras because that gives them practically infinite depth-of-field, from the flower in the foreground to the mountains in the background. The lens on your camera is shorter than that, so you're going to have a hard time blurring portrait backgrounds.

The best I can recommend is to put the camera into Portrait mode, put as much distance as possible between the subject and the background, get as close to the subject as possible, and zoom in to the longest focal length you have (remembering that the last two are in conflict).

Jun 14, 2011 | Canon A1200 Digital Camera


Controlling Depth of Field

A photographed object will only appear sharp in an area a specific distance from the camera. The human eye and brain still accept some areas of the image as acceptably sharp if they lie near the plane of focus and already show a small degree of blur. This zone, which is still in acceptably sharp focus, is called depth of field.

You'd typically want a wide depth of field when shooting landscapes, so as to have everything from the flower in the foreground to the mountains on the horizon in focus. You'd typically want a narrow depth of field for such subjects as portraits and flowers, blurring the background to avoid distractions.

How large this depth of field is depends on the distance to the subject, the aperture, and the focal length of the lens. Whether you're shooting film or digital makes no difference.

If the plane of focus lies further away from the camera, the depth of field is wider than if the camera focuses on an object close by.

Small apertures (large f/numbers) result in a wider depth of field.

Short focal length lenses (wide angle) have a wider depth of field than long focal length lenses (telephoto).

The depth of field is determined by the actual focal length of the lens, not the "35-mm equivalent" often used in the camera specifications. Because most compact cameras have sensors much smaller than SLRs, they have much shorter lenses, giving wider depth of field. This is great for landscapes, not so great for portraits.

To get a narrow depth of field, set the aperture as large as you can (smaller f/numbers), move in close to the subject, and zoom in. If your camera doesn't give you direct control over the aperture, try using the Portrait mode. And yes, the last two items above, moving in close and zooming in, are in opposition, You'll have to decide on the best balance for your picture.

To get a wide depth of field, set the aperture as small as you can (larger f/numbers), move away from the subject, and zoom out. If your camera doesn't give you direct control over the aperture, try using the Landscape mode.

Before going on vacation or shooting your child's wedding, experiment with these factors. Shoot things in your backyard or at a park, trying for both narrow and deep depth of field, then look at the pictures on your computer.

on Jun 23, 2011 | Cameras

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What shooting mode do i need to shoot a subject clear but the background blurred

If you're using the point&shoot modes, use the Portrait mode. For more control you're going to want the PSAM modes.

What you want is a narrow depth of field. Depth of field is controlled by three factors. The first is the lens aperture: the wider the aperture (smaller f/numbers) the narrower the DoF. The second is the lens focal length: the longer the lens the narrower the DoF. The third is the camera-to-subject distance: the nearer you are to the subject the narrower the DoF.

The easiest way to control the aperture is to use the A mode. This lets you set the aperture and the camera will automatically set the appropriate shutter speed to give the proper exposure.

You can zoom in farther and move in closer (yes, the two are in conflict, you'll have to determine the proper position and focal length for the picture you want).

Feb 14, 2011 | Nikon D40x Digital Camera

1 Answer

How do you take a pic with the Nikon d60 where the background is blurred?

You're trying for what's called a narrow depth of field. DoF is controlled by three factors: distance from camera to subject, lens focal length, and lens aperture. The closer the camera is to the subject, the narrower the DoF. The longer the lens focal length, the narrower the DoF. The larger the lens aperture, the narrower the DoF.

Get as close to the subject as practical, and use as long a focal length as practical. I realize these two aims conflict with each other. For portraits, you want a focal length in the 50-90mm range and move in to fill the frame.

You want to shoot with as wide an aperture as you can. Unfortunately most lenses are not at their sharpest wide open. Also, the 18-55mm lens doesn't open up all that wide, f/3.5 at 18mm and f/5.6 at 55mm. To get the widest aperture, you can shoot in the P or A modes. If you don't want to leave the point&shoot modes, try using the Portrait mode.

Since you're not paying for film, I suggest you experiment with the different settings and shooting setups, moving closer and farther from the subject, using different focal lengths, and using different apertures, and see what results you get.

Nov 22, 2010 | Nikon D60 Digital Camera with 18-55mm lens

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I want to take a picture that is focused on the subject, while everything else in the picture is blurry

What you want is a limited depth of field. There are three factors that control the depth of field: subject distance, lens focal length, and lens aperture. The greater the distance, the wider the DoF. The shorter the lens, the greater the DoF. The smaller the aperture, the greater the DoF.

One problem with compact cameras is that they have very small sensors. This means that they have short lenses. And short lenses mean they have wide depth of field. This is often an advantage, in that more of the scene is in focus. Unfortunately, this works against you when you don't want a wide DoF.

At the short end, the S2's lens focal length is 6mm. This will put just about everything in focus. Even at the other end, the focal length is 72mm. With a 35mm film camera, most portrait photographers use lenses at least 85mm in focal length in an attempt to minimize DoF to draw attention to the face and blur the background.

Unfortunately, the best you'll be able to do is to set the camera to the portrait mode, get as close to the subject as possible, and zoom in as much as possible. I realize the last two conflict with each other, you'll just have to find the proper balance for whatever you're photographing.

Nov 18, 2010 | Canon PowerShot S2 IS Digital Camera

1 Answer

How to blur the background in picture taking?

Get another camera :-(

You want to reduce the depth-of-field so that the subject is in focus while the foreground and background are out of focus and blurred. Depth of field (DoF) is dependent on three factors: distance, lens aperture, and lens focal length.

The farther the subject, the deeper the DoF. If you take a picture of a distant mountain peak, the mountain behind that and sunlit the clouds on the horizon will also be in focus. If you get close enough to a flower, you might get the front petals in focus while the petals in the back might blur.

The smaller the lens aperture, the deeper the DoF. Landscape mode, for example, will try to use a smaller aperture in order to get everything in focus while portrait mode will try to use a larger aperture in order to blur the background.

The shorter the lens focal length, the deeper the DoF. This is the killer. Due to the small size of the image sensor, the EX-Z750 has a very short lens: 7.9mm to 23.7mm. Even at the telephoto end of the range, 23.7mm would be considered very wide by film photograpers. A 24mm lens would give film photographers a sharp shot from foreground to horizon and, unfortunately, you're seeing that as well.

Note that the DoF is dependent on the actual focal length, not the 35mm equivalent you may have read about. This is a law of physics, not something that lens designers can easily alter.

Mar 04, 2010 | Casio Exilim EX-Z750 Digital Camera

5 Answers

I want a nature camera

First, to answer your lens question, 400mm is unlikely to be adequate. On a digital camera this is going to give only 6x magnification. Some nature subjects will require much more than that.

Also, do not need a fully featured 'pro' camera. These have features which you may not want. Look at lenses first, and let that dictate the camera.

It rather depends on your intended subject matter, but in general for nature photography (I presume you are thinking of vertebrate animals, rather than plants or insects.) you require very long focal length lenses. This is because wild animals are very difficult to approach, and many are comparatively small as well. As an example, you may only be able to get within 30ft of a heron however well you are hidden, and for a bird that size at that distance a 400mm lens will just be big enough. Just.

As a rule you want to fill the frame. So to work out what focal length you need you need to work out the size of the image in the camera. This is not difficult to work out, as the magnification is only the ratio of the subject to lens distance to the (Thoeretical) film/sensor to lens distance. (Most long lenses are physically shorter than their theoretical focal length. That's the true origin of the word 'telephoto', the lens is optically 'telescoped' into a shorter package.)

In reality this varies a little as the lens moves in and out to focus it, but in practice you just use the focal length of the lens. So for out Heron which is about 10,000mm away with a 400mm lens the magnification is 400/10,000 = 4/100 =.04. A heron is about .5m tall (18inches roughly), and 500mm x 0.05 = 20mm. The hieght of a digital sensor is about 16mm, so that's full height, but a heron is a tall bird, so portrait mode might be better, and that will be closer to 24mm.

So in our example, a 400mm lens will do but only for an animal half a meter in size, if you can get thirty feet away. And that's pushing your luck. (The nearest I ever got to a heron without sitting all day in a hide hoping for it to show was twice that distance!)

Most subjects will be smaller, or further away. Getting within 150ft of a deer in clear view is quite a challenge even for an expert stalker. At 1.5m tall with a 400mm lens, the image will be 12mm high. If the subject is a grizzly bear, then I doubt you would want to be that close.

Of course if you are wanting to photograph smaller animals, then the problem is compounded. Especially if they are easily spooked.

In essence you want as long a lens as you can manage, so you can photograph from a comfortable (for the amimal) and safe (grizzly bear) distance. However, as in many instances you won't be able to control that, and the range of animals you want to photograph will vary in size, you really want either more than one lens, or a really good zoom.

Really good zooms of long focal length are very expensive, so two lenses might be a better option, or a long lens with a factory matched multiplier would be almost as good. (Zoom lenses cannot perform at optimum over all the focal lengths available, so really good ones are difficult to design and make.)

So you first need to decide what focal lengths you need.

Then you have to consider camera shake. As a rule of thumb you need an absolute minumum shutter speed of 1/(focal length in mm) for hand-held shots. As you will be using long lenses, with small apertures, you won't be able to take shots hand held.

One (partial) solution is to use an image stabilized or shake reduced system.

Image stabilization is built into the lens, and works by moving optical elements to compensate for vibrations. This makes the lenses much more expensive, and will eat batteries. This has the advantage that it is always optimal for the lens.

Shake reduction moves the sensor in the camera, to achieve the same effect. It makes the camera a little more expensive, but the lenses are a lot cheaper, and that's where most of your money will go!

(Note, that digital image shake compensation is not the same thing, and reduces the image sharpness.)

Of course the traditional solution is a really sturdy tripod. Most tripods are simply not up to the job, so you need to check out as many reviews as you can. But be aware a really good tripod will not be cheap.

The camera mount must be really rigid if the camera is not to move during exposure (A camera with a mirror-up function can help. The mirror is the Major source of vibration in a camera, this allows the mirror to flip well before the shutter fires allowing time for vibration to die away.) and the tripod itself must not flex or twist.

A tripod with the means of suspending a weight underneath is useful, extra weight will make sure the tripod feet are firmly placed and help pre-stress the tripod so any residual 'slack' is taken up. (A simple hook that you can hang a kit-bag on will suffice!)

A good tripod and head could cost £200 or more alone!

As for selecting the lenses....

Canon do some very long focal length lenses but they are also very expensive (£2000+) These include a zoom with image stabilization, and a dedicated multiplier to double the range. A good used example will cost over £1000.

However, you should be aware that Canon are generally quite expensive, and other manufacturers produce similar systems, at various prices. I would look at Nikon, and Pentax, these brands are still well regarded.

Jan 23, 2009 | Canon EF 70-200mm f/2.8L IS USM Autofocus...

1 Answer

Image Properties shown....You've been great!!!! Few more....

1: it just adds and copies existing pixels with the digi zoom. I never fooled with it for you can just take the image with a paint program and blow it up as big as you want.. with decreasing detail.just start with a nice high megapixel like 5M camera but you'll need a bigger memory card.

2: exposure bias at 0.0 is what the camera sets as standard. adjusting this in the "M" mode allows more exposure "+" or less "-". making the aperture bigger or smaller to allow more light or less at higher shutter speeds or low speeds. 1/100 is good.
3: yes but try it out and put it on automatic first.
4: focal length or f stop I'm confused. The aperture setting is known as the f-stop. The lowest number f-stop lets the most amount of light reach the image sensor. A high f-stop increases the depth of the field.witch is focal length. so I think I was wrong in the "feet" meaning f/2.8 for portrait or up close f'/16 for front and background or landscape. also set your ISO around 80 - 120 for the best exposures or pictures.

May 10, 2008 | Cameras

1 Answer

Slight blur shooting variety of subjects

It is just a possibility but you may have overrode the auto focus. If you accidentally move the focussing ring it disables the auto focus.

Mar 17, 2008 | Nikon 18-200mm f/3.5-5.6 G ED-IF AF-S VR...

1 Answer


What is the focal length of your lens?

In order to work with depth-of-field, two things are essentially contributors to fully focused image without depth, 1) it depends on your lens focal length 18-70mm or 70-200mm, 2) your f-stop. 2.8 (large iris) or 30 (small iris).

Simply put, a smaller iris (>15 fstop) increases the DOF, or makes things in front-of and behind the subject more visible/clear. Larger iris (<15 ftop) reduces the DOF, or makes things in front-of and behind the subject less focused/recognizable.

There's quite a lot that goes in to DOF, so check out the link above for the details.

Nov 13, 2007 | Nikon D50 Digital Camera with 18-55mm Lens

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