Blurry Photos When Using AV Mode

[ruta_nonacs]

I just got a canon rebel XTi, and while sometimes works great, I am frequently

having problems with grainy or blurry shots when using the AV mode. I can't

figure out what I am doing wrong.

1. Shutter speed is OK. The problem can occur when the shutter speed is 1/200.

2. It occurs with multiple lens, the kit lens, as well as a Canon 50mm f/1.8.

3. It can occur at ISO 100, 200, 400.

4. I have switched the focus to the center point.

5. On a given lens, it can occur at any depth of field.

It does not always occur and tends to occur most in low light situations, not

super low light but even at dusk or on a cloudy day. What I can't understand

is, when I use the program mode I don't have the problem at all. Is it me or

the camera? Thanks for your help.

[awindsor]

Grainy normally indicates underexposed. Blurry normally results from slow shutter speed due to handshake. I am surprised that you are seeing shake at 1/200 sec. P mode should not be different from Av mode except that it will open the aperture before letting the shutter speed drop below 1/60 sec.

 

Can you post an example with EXIF?

[ruta_nonacs]

Here is a typical example: f/5.6, ISO 200, exp 1/100.<div></div>

[albert lui]

Ruta,

 

In your sample image, the EXIF indicates 1/100 shutter speed and 85 mm focal length. Since the XTi is a 1.6x crop camera, the minimum shutter speed should be 1/(85*1.6) = 1/136, according to the 1/FL rule (with FL taking the crop factor into account). This may be a factor in causing image blurriness. Halving the 1/FL rule, for 1/250, would be even better.

[bryantan]

Motion blur is not the primary problem, the point of focus is at the extreme foreground.

[elliot1]

Stop using AV mode, set your shutter speed to at least 1/250 or 1/500 and adjust your ISO up to allow for properly exposed pictures. See if that helps.

[chrisjb]

Hi, to me the settings should be ok, if the subject is moving possbly was focussed then moved out of focus before shutter pressed. maybe try A1 servo see if that helps with moving subjects. Faster speeds won`t help if there is a gap between focus & shoot, but it may help with some motion blur. Also take notice of how quickly you use the shutter, don`t jerk it as tryiny to get a quick shot. hold the body tight make sure only your trigger finger is moving...HTH

[mike_stemberg]

Ruta, may I ask what lens was used for this shot? The reason I ask is that I've sometimes wondered if the EXIF data as read by Photoshop considers the 1.6 x crop or not. (On a side note..I have also never tested or checked out if e.g. Canon's DPP shows identical data.)

[maddalice]

i think it is not focus proper.it was my eys when i was looking in the veiw finder so i moved the wheel.thank u.alice.

[chrisjb]

Hi Mike, a lens is a lens is a lens, never changes focal length, all exif that I`ve seen says what FL the lens is, so if 85mm in exif it should be 85mm. If someone knows different I`m always learnin.

[JeffOwen]

Check that the lens was set to AF (auto focus) and that either all the focus points are set or just the centre one. As Bryan says the focus is the main issue and the shot is focused down the bottom of the image.

[KenPapai]

A basic book on photography is all you need Ruta. Cameras are not magical tools no matter how new they are.

[steve_dunn2]

<p>The camera tags the image with the actual focal length. I believe this is a requirement of the EXIF specs, though I'm not 100% certain about that. Some cameras (at least some Nikon DSLRs, for instance) throw in an additional tag which gives the 35mm-equivalent focal length; I can't speak for all Canon DSLRs but at least my 20D does not indicate the equivalent focal length in the EXIF data.</p>

[ruta_nonacs]

Thanks for all your comments. I don't think it is too slow a shutter speed, as I have many shots at a slower shutter speed (taken with the program mode) which have come out perfectly clear.

 

I think the most likely explanation is that I am allowing too much (or too little) time between focusing and releasing the shutter. The other possibility is that my camera is not focusing properly or consistently.

 

I am not expecting magic, but I am frustrated that at this point my canon G2 takes pictures that are better than the DSLR. Thanks for your help.

[alfaromeo]

this is not a slow shutter speed or blur from the hand shake for sure. The foreground is perfectly sharp. Most likely focusing error. Shoot the non moving object at the same settings and see what happens.

[mike_stemberg]

<p>Ruta, it's a pity you did not see my request asking to know what lens you used for that shot. I re-read your first posting and you had mentioned 'kit -lens' (the standard 18-55mm possibly ...or not?) and also the 50mm 1.8. But no matter. I opened your image with Canon's Zoom Browser which has a function to show where the focus point/s were for an image, but somehow that data was not avaiable for that particular image for me. Perhaps if you opened it yourself with the Zoom Browser , read the Shooting Properties, and also clicked on the icon to the left of that, that would /should show you the focus point/s selected. Such information can help you decipher and analyse things about your photography.<p>

 

 

<p><i>"a lens is a lens is a lens, never changes focal length"</i><br>Sure thing, unless it is a variable focal length length!</p>

 

<p>Steve, Thank you for your measured response, I think you understood where I was coming from or where I wanted to go. Anyway, after this posting and the responses, I did what I should have done in the first place. I shot three images using a Canon XTi/400D, the first with

a fixed 50mm 1.8, another with a 17-85mm set at 17mm. and a third at 85mm FL.<br><br>

The Exif data readings:<br>

I opened these images with Canon's Zoom Browser and Photoshop ...and in each instance the Exif focal length data shown were ..50mm, 17mm and 85 mm.<br>

 

So now I know that the crop factor (1.6x for my camera) were NOT taken into account both by Canon's (own) Zoom Browser or by PhotoShop!</p>

[koen_van_den_beld]

The problem with this photo is the focus is off. There is no problem with blur. You say that the camera takes perfect photos in P mode so the problem is not the camera or the lens and the only option remaining is that this is a case of user error.

 

The girl is walking away from you and I think you half pressed the shutter button then checked your exposure for a second and then did a full press. In the meantime the girl walked too far away to be in good focus. You should check your exposure before you half press the shutter or release it and half press it again. You can refocus as many times as you want before pressing the shutter completely.

Alternatively you can use AI servo focus mode for moving subjects.

[chrisjb]

Mike not sure if this will help

 

Model: Canon EOS DIGITAL REBEL XTi

Camera serial number: 1120621799

Firmware: Picasa 3.0

Date/Time: 2006:10:05 21:49:46

Shutter speed: 1/100 sec

Aperture: 5.6

Exposure mode: Av

Flash: Off

Metering mode: Evaluative

Drive mode: Continuous

Self-timer: 65 secs

ISO: 200

Subject distance: 3.57 m

AF mode: AI Focus AF

Focus point: [- < - - -]

Image size: 1880 x 2816

Image quality: Fine

White balance: Auto

Color space: sRGB

Custom Functions:

Default settings

 

Also a screen shot of the focus point, bear in mind the FP is recorded when the realease half pressed, If the subject moves or the shot is recomposed, you will not get an accurate account.

 

kind regards

[chrisjb]

Also 3 different exif viewers say just FL 85mm.

[chrisjb]

I believe the EX580 may take x1.6 crop factor into account, haven`t check mine tho. be interested if the new bodies do.

[luis_benites]

Hi Ruta, what focus point did you choose for this photo?. The camera took a sharp photo of the ground with very narrow DOF.

 

I recommend manually choosing the focus point for each photo instead of relying on the camera trying to read you mind. The odds are about between 1/9 - 1/5 that it'll come out ok using the mind reading circuit of the camera.

 

Digicams have very wide DOF so it matters less what focus point the camera chooses.

 

Luis

[mike_stemberg]

Ruta, according to chrisJB's screenshot attachment, you had the focus point way out...<br><br>

 

... and chrisJB, I would be most interested to know, (even though this is the slightly off-topic to Ruta's preliminary query) what was the FL as shown by Picasa .. your screen-shot doesn't show this . In any case, other than Lightroom, Canon's Zoom Browser and Photoshop not working as they should, I now believe that these things do not take the camera's crop factor into account when interpreting FL.<br><br>Regards~ Mike<br><br><i>PS. Ruta, I am still curious (only slightly) as to what lens you used for this shot?</i>

[bryantan]

Mike,

 

The lens was the 17-85, as Adobe Bridge shows. 1/100 with IS turned on would have been plenty fast enough. However, even if focused properly, I don't think you can expect too sharp of an image when shooting wide open at the long end of the lens.

[john_g10]

@chrisJB: what software did you use to get the focus points ?. Thanks!

[chrisjb]

Hi John, it was with `BreezeBrowser` mines an older ver. 2.12.1 but will upgrade to Pro ver with new PC. Canon zoombrowser show them on my PC when 1st downloaded. but looses the info once they have been in PS. here`s a link

 

http://www.breezesys.com/

 

hope this helps.

 

regards