flower- focus issue

[Atavar]

I have had a devil of a time with this. First off let me admit i am an absolute neophyte with digital photography. This particular photo gave me fits as I could not get the focus on the blooms themselves, but on multitudinous attempts was able to get every green leaf in the garden *except* the pink blooms in perfect focus. i did mount the camera on a tripod and tried putting the focus square in the viewfinder on various parts of the pink blooms, but no matter what i did the camera seemed to strongly prefer green bits as the focus object. Is this the phenomenon I see referred to as front/back focus?
I am shooting with a Nikon D5200, and did not use manual focus, which would have worked but I really want to master the tools available in the camera. Any instruction you can provide would be most greatly appreciated. I am more interested in technical mechanics at this point, but I will note any artistic criticism also.
Also, what size should photo's be for attaching to posts like this? Pixels? DPI? I really am a digital noob and appreciate your wisdom.


BTW, this plant was a volunteer found in my rose garden, an 8x8' inset between the porch and the garage at the front of the house. I did not plant this, and it was lucky it bloomed before it was weeded. Angle and lighting options were very limited, as working deep in a tangle of rosebushes can be hazardous to one's epidermis and I don't know if the D5200 is blood proof.

 

[tirediron]

Sounds odd, about the only explanation that I can offer is that perhaps for some reason the camera's AF sensor didnt' find enough contrast in the bloom ('though it certainly appears as if there is enough that it should have worked). Front/back focus is an issue that arises when your AF system is slightly "out of tune" and the camera [usually very slightly] focuses in front of or behind the subject, while indicating that focus is where it should be.

Optimum posting size for images is 800 pixels on the longest side.

 

[Atavar]

---- Image Information ---------------------------------------------------------
Filename: DSC_0039c.JPG
File size: 217 KB (222 457 bytes)
Dimensions: 1024 x 637
Bit depth: 24
Created: Friday, June 07, 2013 11:24:21 AM
Changed: Sunday, June 09, 2013 12:43:00 PM


---- Description ---------------------------------------------------------------


---- Picture Taking Conditions -------------------------------------------------
Audio note No
Camera data Yes
Text information No
Created Friday, June 07, 2013 11:24:21 AM
Digitized Friday, June 07, 2013 11:24:21 AM
Modified Sunday, June 09, 2013 12:42:58 PM
Flash Yes
Exposure time 1/200 s
Aperture 4.5
Max. aperture 4.59
Focal length 110.00 mm
Focal length (EQ35mm) 110 mm
ISO 800
Digital zoom ratio 1.00
Exposure bias -1
Metering mode Pattern
Exposure mode Auto exposure
White balance Automatic
Exposure program Aperture priority
Orientation Normal
Sharpness Normal
Contrast Normal
Saturation Normal
Gain control Low gain up
Scene capture type Standard
Camera Make NIKON CORPORATION
Model NIKON D5200
Software Ver.1.00
Compression JFIF Compression
Color representation YCbCR
DPI 300.00
Exif version 2.30
Flashpix version 1.00
Colorspace sRGB
Flash - detailed Flash fired, Strobe return light detected, Compulsory flash firing
Sensing method One-chip color area sensor
File source Digital camera
Scene type A directly photographed image
Custom image processing Normal process
Subject distance range None
Image Unique ID 199
Lens 55.00 - 200.00 mm f/4.0 - 5.6
Keywords No
Digital signature No
Flash bias 0

Picture Style STANDARD
Colorspace 1

 

[Derrel]

It can be very tricky to get precise depth of field placement sometimes. If the camera is angled downward, for example, even a bit, at close distances like this, the "usable" depth of field zone will be VERY limited on 3-D subjects like this plant. At close distances, and wide apertures, any angle of the camera can leave the user with a very shallow zone of focus, with much of the depth of field zone above, and behind, the subject on the top part of the frame. And, on the bottom of the frame, a preponderance of the DOF zone will be in front of the subjects placed in the lower portion of the frame. At f/4.5, at this distance, and at the longish focal length used, there will be VERY little in sharp focus. Even a few degrees' worth of downward tilt of the camera lens will skew, forward and behind, the plane of depth of field, and on a subject like these flowers, f/4.5 will give you fits.

I can tell from experience that a much smaller f/stop would be more in order if the goal is to shoot a close-range shot like this, with all of the pink blossoms in acceptable focus.

 

[Atavar]

Thank you all, I do greatly appreciate the help. If the blooms still exist when I get home I will try again with a smaller stop and a shorter lens. I can see how getting closer physically instead of optically would benefit this, if the rose bush thorns will let me in there..
I truly wasn't thinking in 3D space and what Derrel says about the DoF plane (is that the right term?) makes a lot of sense. I will have to keep that in mind and perhaps mentally project the shutter plane forward to the subject when taking pictures.

This is where the lack of a DoF preview on the D5200 really sucks. I still keep looking for it on the camera, just because every automatic (non-P&S) camera I have ever owned has had that feature, but I have read in several places that it does not exist on the D5200.