Should I be worried?

[norcal99]

I received my 70-200 f/4L in the mail today and wow, this is one good looking/hefty lens! However, I took some test shots and I think i might have a focusing problem. Here's a few pictures to show what I mean:

1) 200mm @f/4 (100% crop)
http://www.mustangmods.com/data/1593/bird_crop.jpg

2) 200mm @f/4 (100% crop)
http://www.mustangmods.com/data/1593/measure_crop.jpg

From the first one, it looks as if the lens has a bit of back focus but the measuring tape in the 2nd one looks spot on. Maybe I was shaking? Do you think it needs calibration?

-Mike

[norcal99]

Info on the first shot is: TV (1/180), f/4.0, ISO 100
Info on the second is: TV (1/15), f/4.0, ISO 100
Both taken with a D60 if that means anything

[tim]

Assuming you're focusing on the 16, it looks ok. I wouldn't worry about the first image too much. If you post the first image again with full exif data i'll take a look at that too - in Photoshop resize it down then "save as" instead of "save for web".

[norcal99]

For the ignorant, how do I find out the EXIF?

[joeseph]

what focussing point are you using? all 3 or just center spot?

[Phil V]

In the first one the camera focussed on the leaf to the side of the bird, a much contrastier subject than the bird. That's exactly what I'd expect it to do. If you'd have picked the centree focus point, looked at the focus at exposure time, you could have moved the camera slightly, the bird would have popped into focus. The second image shows your lens focusses perfectly.

Just remember the focus points are a cross shape and not exactly the same shape and size as the squares in the viewfinder. And also that the camera will 'always'** pick the wrong focus point. We've all got drawers full of out of focus prints, why do you think all your shot's should be perfect? Practice, then read the manual, then practice some more, then read some more books, then practice some more, then read some more on the internet, then practice some more, then read some more books, then practice some more.

** Murphy's law.

[tim]

Just post like I said above - open the original in Photoshop, resize down to 640*480 or so, use "save as" instead of "save for web" in photoshop, quality can be as low as you like, makes no difference to the exif.

What I want to look at is the actice focus point.

[norcal99]

EXIF for #1

ExposureTime : 1/15Sec
FNumber : F4.0
ISOSpeedRatings : 100
ExifVersion : 0220
DateTimeOriginal : 2005:04:27 22:52:38
DateTimeDigitized : 2005:04:27 22:52:38
ComponentConfiguration : YCbCr
CompressedBitsPerPixel : 3/1 (bit/pixel)
ShutterSpeedValue : 1/15Sec
ApertureValue : F4.0
ExposureBiasValue : EV0.0
MaxApertureValue : F4.0
MeteringMode : Division
Flash : Not fired
FocalLength : 184.00(mm)
MakerNote : Canon Format : 908Bytes (Offset:942)
UserComment :
FlashPixVersion : 0100
ColorSpace : sRGB
ExifImageWidth : 2048
ExifImageHeight : 1360
ExifInteroperabilityOffset : 1866
FocalPlaneXResolution : 2048000/892
FocalPlaneYResolution : 1360000/595
FocalPlaneResolutionUnit : Meter
SensingMethod : OneChipColorArea sensor
FileSource : DSC
CustomRendered : Normal process
ExposureMode : Auto
WhiteBalance : Auto
SceneCaptureType : Standard
Focused AF Area(AiAF) : Center

[tim]

Chalk it up to user error. Take some more shots and see how they go.

[norcal99]

Chalk it up to user error. Take some more shots and see how they go.

Thanks a lot for taking time to answer my questions. I just thought about the first picture though and I remember the bird was coming towards me. I didn't have AI servo on which might be the reason why the bird's out of focus. So yeah, probably user error. I'll take some more pictures tomorrow and report back.

Thanks!

[tim]

No problem, it's always useful to get a 2nd/3rd/4th opinion for these types of things.

[Jopox]

I also had a similar problem with my 70-200 F4L on my 20D (both which I've had for less than a month), specifically on close-ups of various flowers, stopped down to F4. Shades of the backfocus problem that I've read about in other fora/posts, which naturally made me concerned. After going over all the photos I've taken, I realized that the front of the lens was within the minimum focusing distance, thus making the center out of focus. Aside from this problem of close-ups, most of my other shots are really, really clear.

I've been using a Canon A-1 film SLR for the past 20 years or so, and switched to the 20D just this past month. Being new to AF, it sure needs quite some getting used to...:)

[O/confusion]

EXIF for #1

ExposureTime : 1/15Sec



If this is really your shutter speed setting for the first exposure (the bird), then I'm not surprised the shot is blurred. At this speed, and with this lens, the slightest amount of camera or subject movement during exposure is almost guaranteed to give this kind of result. Are you sure this is the correct EXIF file for this image?

regards,
Terry

[JZaun]

Looking at your EXIF, you shot at 1/15th of a sec on a moving bird. That won't work. Even when they walk slow birds are quivering and shaking. 1/15 will get the still object if you can hold it but not the bird. I never shoot birds slower thatn 125 and prefer 250 and up. Also at F4 your DOF is so shallow you may miss a lot of the bird being in the focus range.

JZ

[norcal99]

You're right! The EXIF doesn't appear to be correct for some odd reason. The playback on the camera shows 1/180. There's no way that picture would have come out remotely clear hand held at 1/15th of a sec.

[raylks]

Sometimes when you have lock the focus by half pressing the release and then recompose the subject the focus may be lost. This was my experience with my 300D.

You shall check whether or not during recomposition the focus has been lost. If you are shooting with 20D, 350D, or 1D series, shoot in one shot mode to check the focus accuracy.