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Esteemed Contributor
Posts: 3,129
Registered: ‎06-11-2013

Re: why does my camera (EOS REBEL XS) take blurry pictures

The "f/number" is sometimes called the "f-stop" or "focal ratio".  On your camera, it's labeled "Av" for "Aperture value".  

 

The value is a ratio... specifically it's the ratio of the focal length of the lens (in millimeters) divided by the diameter of clear aperture (also in millimeters).  e.g. if you had a 50mm lens with a 25mm wide aperture, then that would be "f/2" because 25 divides into 50 twice.  If you had a 100mm lens and the aperture was still 25mm then that would be f/4... 25 divides into 100, four times.

 

The smaller the opening (relative to the focal length of the lens), the higher the ratio, the smaller the opening.  This is one of several factors that influence the range of distances at which a subject will appear to be more-or-less in acceptable focus.  

 

E.g. suppose I focus the camera for a subject which is 10' away.  It turns out things which are only 9' away or as far as 11' away might also appear to be focused.  That range is called the "depth of field".  

 

If we happen to be using a 50mm lens and f/4... that above example (focus at 10' get a depth of field from roughly 9' through 11') is what we'd get.  

 

BUT... if we increase the "f/number" (Av) to, say, f/11... then the depth of field increases to about 8' through 13.5'.   At f/16 it increaases even more... 7.3' to 15.7'.

 

Alas there is no free lunch.  Everything is a trade off.  In this case, the trade-off caused by decreasing the size of the aperture opening (and thus increases the depth of field) is that you also reduce how much light can enter the camera when the shutter is open and that means you'll either need to shoot at a slower shutter speed (possibly too slow for hand-held shots) -or- you may need to increase the ISO sensitivity of the camera (which increases the amount of "noise" visible in the image).  

 

This concept of balancing the ISO, shutter speed, and aperture size is all part of understanding "exposure" values.

 

The book "Understanding Exposure" by Bryan Peterson might be especially helpful to you in understanding how to know what camera setting you might change to get the results you want.  

 

Tim Campbell
5D III, 5D IV, 60Da
New Contributor
Posts: 1
Registered: ‎03-14-2017

Re: why does my camera (EOS REBEL XS) take blurry pictures

[ Edited ]

When i take a picture indoors the picture looks good. But when i zoom it in to look at it it is blurry.

I have the camera set on full auto.

It is the Cannon EOS Rebel XTI.

I am new to this and don't understand a lot about the Camera.

I also got a 75-300mm Tramron lens and it will only shoot to 200mm.

Anything above that the camera shows ERROR.

Weird

Is it something i am doing wrong.

Please E-Mail me as i won't find this page again

My E-Mail is [MOD NOTE: Email address removed per FORUM GUIDELINES]  all lower case

Thank You So Much

Jan Allen Sr

VIP
Posts: 8,242
Registered: ‎12-07-2012

Re: why does my camera (EOS REBEL XS) take blurry pictures

"I also got a 75-300mm Tramron lens and it will only shoot to 200mm."

 

The Tamron is probably not compatible with your Rebel.  That is the chance you take when you buy third party lenses and gear.

 

"But when i zoom it in to look at it it is blurry."

 

I would bet they are blurry even when you don't zoom in.  You just don't notice it as much.  The biggest cause of blurry indoor photos is not enough light which slows the SS down too much.  More light or a real flash are two remedies if a higher ISO doesn't help.

A lot of Canon stuff. Along with, a lot of other stuff.
Honored Contributor
Posts: 5,614
Registered: ‎08-13-2015

Re: why does my camera (EOS REBEL XS) take blurry pictures

[ Edited ]

"I also got a 75-300mm Tramron lens and it will only shoot to 200mm."

 

If it stops working above 200mm, what is the range of "f/stops" listed on the lens?  It might be written as a ratio like this " 1:4.5 - 1:6.3 ".

 

The built in flash on your camera is fairly weak.  It has a range of 10 feet, or less.  And, because the built-in flash is so small, and does not raise up very high, some long lenses will cast a shadow into the photo, which I suspect your 70-300mm lens may do. 

 

Your 70-300mm lens is fairly "long", which refers to the focal lengths, for your camera body.  That range of zoom is considered to be medium telephoto  I would suggest getting a "standard" range of zoom lens, which for your camera body are focal lengths ranging roughly from about 18-55mm.

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
New Contributor
Posts: 3
Registered: ‎06-04-2017

Re: why does my camera (EOS REBEL XS) take blurry pictures

I also need help mine is blurry also
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