Help on focus
May 2, 2012 11:31:47 #
I just received my new 150mm sigma macro. Been snapping with it a couple of days now and it seems none of my pics are really in focus. Tried manual focus and auto but the pics are soft. Have a Nikon D-300 ; Sigma 150mm micro with image stabalization. Any suggestions what I might be doing wrong or what ideas might make pics better?
May 2, 2012 11:37:25 #
Could you please post a photo or two along with your settings such as ISO, f-stop, and shutter speed.
There are so manylittle things that could be a problem.
There are so manylittle things that could be a problem.
May 2, 2012 11:45:48 #
It is likely you have a bad Sigma. All third party lenses tantalize with low price, but only occasionally have stellar performance. I have a top of Tokina's line 28-70 f/2.8 zoom, and the Nikkor 28-70 f/2.8 zoom, and the extra $1,000+ is night and day obvious in the unbelievably superior quality of the Nikkor. The Tokina simply was not sharp, and could not be made to be sharp with small f/stops like f/8, 11 or 16. Crisp edge detail and the essence of what sharpness looks like is an attribute usually reserved to brand name lenses.
Another, rather famous example: Hasselblad is a revered medium format camera. In the Zeiss made lens lineup, there was once upon a time a 150mm f/4. This Zeiss lens came in two versions: REALLY, REALLY, INCREDIBLY SHARP, and unfortunately, the second variation was SOFT and LOUSY. It was a matter of the draw as to which 150 you got. I lucked out, fortunately.
Another, rather famous example: Hasselblad is a revered medium format camera. In the Zeiss made lens lineup, there was once upon a time a 150mm f/4. This Zeiss lens came in two versions: REALLY, REALLY, INCREDIBLY SHARP, and unfortunately, the second variation was SOFT and LOUSY. It was a matter of the draw as to which 150 you got. I lucked out, fortunately.
May 2, 2012 18:08:50 #
fricciardi wrote:
I just received my new 150mm sigma macro. Been snapping with it a couple of days now and it seems none of my pics are really in focus. Tried manual focus and auto but the pics are soft. Have a Nikon D-300 ; Sigma 150mm micro with image stabalization. Any suggestions what I might be doing wrong or what ideas might make pics better?
Hi fricciard: A couple of questions come to mind. First are you using a tripod or are you hand holding the camera? Second When photographing an extremely small subject the smallest movement will affect the shot. Was it windy or did the subject move in anyway, hand shake, mirror slap, even a little extra pressure on the shutter button can cause blurring to one degree or another. Hope this helps.
May 2, 2012 19:19:02 #
Here's my take on focus from my ebook Photography 101 and beyond":
1.Set your Focus icons - detach lens, (so you are adjusting focus on focus point, not image) - adjust dioptre (next to viewfinder) so focus points are sharply in focus. (easier against a white, or light background) Re-attach lens
2. All modern cameras have Auto-focusing, which works very well, but there are times when you need to focus manually. For auto-focus to work properly it requires a certain amount of contrast, if the contrast isnt adequate you will need to focus manually.[ NOTE: In your cameras viewfinder, depending on camera-flagship models generally have many focusing spots, and lesser, entry-level dslrs will have around 5 focusing spots. With lens wide open, any of these spots can be used for selecting where to auto focus-But, depending on maximum aperture of lens in use, the ones you are able to use get fewer. Top-of-the-line cameras will only have the centre spot usable at F8,and entry level cameras at F5.6, and less than that, even these single spots arent reliable.]
Actually it is more beneficial to set auto focus by the centre spot, then re-compose, rather than use the peripheral spots-The reason being that only the centre spot has vertical and horizontal pixel rows. This means that if you use the peripheral spots (top and bottom spots have horizontal pixels only and right and left spots have vertical pixels only) To focus, you must have a part of the scene crossing a line of pixels at 90 degrees, and the centre spot gives you a more accurate reading ,having both vertical and horizontal pixels) It will pay you to manually focus most of the time, for full control of the situation. For instance, if an unnoticed reed encroaches into your image, when your are shooting a swan at the lake, for instance, your lens may auto-focus on that reed, rendering your actual subject out of focus.
There are times, you will find when auto focus will fail to respond favourably-although auto focus is able to lock on to any subject, there are certain conditions where it may not be possible ,even when the indicator lights are on, and the shutter releases/
Subjects with low contrast
Subjects in excessively bright light
Two subjects at differing distances
Subjects with repetitive patterns
High speed subjects at close range
To ensure you are in focus, there, in the viewfinder, is the electronic rangefinder icon, that comes on when you are in focus. NOTE: Each lens has its sweet-spot, that is when the aperture and zoom length combine to give optimum sharpness- 18-55 mm zooms usually have this sweet-spot at the 35mm distance setting and 2 stops back from wide open. On a 70-300mm zoom the sweet-spot would be around 185-200mm aperture 2 stops back from widest.
Auto focus is good for situations where you cannot focus fast enough, manually, such as sports and wildlife photography.
Depth of field appears to be the most confusing of focus elements. Depth of field is a range of acceptable sharpness in an image, from near to far. Three factors control Depth of field: Aperture: The wider the aperture, the shallower the depth of field. Focal length of lens, The longer the focal length of the lens, the shallower the depth of field will be. and Distance from subject, Landscape images have great depth of field, whereas Macro (extreme close-up) images have very shallow depth of field. Concerning depth of field, Hyperfocal distance seems to be even more confusing -Hyperfocal distance is a point of focus where at a certain aperture, Half the distance from that point to Infinity, (which starts at 30 feet, and extends to as far as you are able to see)) will be in acceptable focus, The best lenses for hyperfocal distance are 80mm or wider ; telephoto lenses, because of their relative short depth of field, are rarely used. (Prime lenses have a scale on them for this, zooms do not) Using a 18mm setting on your zoom lens at f11, Hyperfocal distance is somewhere around 5 feet (1500mm), so depth of field at this aperture would be from 2 1/2 feet ( 750mm) to infinity, when focused at 5 feet. A good guideline for great depth of field for landscapes is to use the bottom focusing marker in your DSLR viewfinder, (either horizontal, or vertical) as this will focus 1/3 of the way into the distance, (It is on the lower third imaginary Rule of Thirds gridline!) ,as is usually recommended. [ NOTE: Unless your camera has depth of field preview, looking through the viewfinder all will not be in focus, because your lens, until you press the shutter button to make the shot, will be open at full aperture.]
To avoid camera-shake, always use a sturdy tripod. When using lenses equipped with VR/IS (vibration reduction-Nikon/Image stabilisation-Canon), on a tripod you will need to turn off the anti-shake, or lens will still try to counteract vibration that isnt there,, and cause unwanted shake. If, for some reason you cannot use a tripod, use your self as one-
Feet at T-Stance, left hand supporting camera, elbow against ribs
Camera pressed against nose and brow
Right hand also elbow against ribs, index finger on shutter button
Set shooting mode to continuous, and Roll index finger on shutter button - First couple of shots will probably be blurred, but somewhere between 3-4 and 5 you should have a shake-free shot of the scene. ( When using zoom lenses longer than 200mm-I usually set ISO to 400, when hand-holding)
Trap focusing: (Nikon Only)
This is a neat way to use auto focus especially for fast sports/wildlife action.
Custom (pencil) menu:
Autofocus set to AF-S
AF area mode set to single
AE-L/AF-L set to AF ON
Compose your shot and set the focus by aiming the centre focus icon at a definite target at the precise distance you want, (Say a tree branch where a bird is about to land, or on second base where the baseball player's foot will land) and pressing the "AE-L/AF-L" button near the viewfinder. This will focus the lens, let go of AE-L/AF-L button. Turn away,
press and hold the shutter button all the way down. Point camera at pre-focused point when subject approaches, and your camera will take the shot (or shots, if you are in continuous shooting mode.)
Much faster than Human reflexes.
1.Set your Focus icons - detach lens, (so you are adjusting focus on focus point, not image) - adjust dioptre (next to viewfinder) so focus points are sharply in focus. (easier against a white, or light background) Re-attach lens
2. All modern cameras have Auto-focusing, which works very well, but there are times when you need to focus manually. For auto-focus to work properly it requires a certain amount of contrast, if the contrast isnt adequate you will need to focus manually.[ NOTE: In your cameras viewfinder, depending on camera-flagship models generally have many focusing spots, and lesser, entry-level dslrs will have around 5 focusing spots. With lens wide open, any of these spots can be used for selecting where to auto focus-But, depending on maximum aperture of lens in use, the ones you are able to use get fewer. Top-of-the-line cameras will only have the centre spot usable at F8,and entry level cameras at F5.6, and less than that, even these single spots arent reliable.]
Actually it is more beneficial to set auto focus by the centre spot, then re-compose, rather than use the peripheral spots-The reason being that only the centre spot has vertical and horizontal pixel rows. This means that if you use the peripheral spots (top and bottom spots have horizontal pixels only and right and left spots have vertical pixels only) To focus, you must have a part of the scene crossing a line of pixels at 90 degrees, and the centre spot gives you a more accurate reading ,having both vertical and horizontal pixels) It will pay you to manually focus most of the time, for full control of the situation. For instance, if an unnoticed reed encroaches into your image, when your are shooting a swan at the lake, for instance, your lens may auto-focus on that reed, rendering your actual subject out of focus.
There are times, you will find when auto focus will fail to respond favourably-although auto focus is able to lock on to any subject, there are certain conditions where it may not be possible ,even when the indicator lights are on, and the shutter releases/
Subjects with low contrast
Subjects in excessively bright light
Two subjects at differing distances
Subjects with repetitive patterns
High speed subjects at close range
To ensure you are in focus, there, in the viewfinder, is the electronic rangefinder icon, that comes on when you are in focus. NOTE: Each lens has its sweet-spot, that is when the aperture and zoom length combine to give optimum sharpness- 18-55 mm zooms usually have this sweet-spot at the 35mm distance setting and 2 stops back from wide open. On a 70-300mm zoom the sweet-spot would be around 185-200mm aperture 2 stops back from widest.
Auto focus is good for situations where you cannot focus fast enough, manually, such as sports and wildlife photography.
Depth of field appears to be the most confusing of focus elements. Depth of field is a range of acceptable sharpness in an image, from near to far. Three factors control Depth of field: Aperture: The wider the aperture, the shallower the depth of field. Focal length of lens, The longer the focal length of the lens, the shallower the depth of field will be. and Distance from subject, Landscape images have great depth of field, whereas Macro (extreme close-up) images have very shallow depth of field. Concerning depth of field, Hyperfocal distance seems to be even more confusing -Hyperfocal distance is a point of focus where at a certain aperture, Half the distance from that point to Infinity, (which starts at 30 feet, and extends to as far as you are able to see)) will be in acceptable focus, The best lenses for hyperfocal distance are 80mm or wider ; telephoto lenses, because of their relative short depth of field, are rarely used. (Prime lenses have a scale on them for this, zooms do not) Using a 18mm setting on your zoom lens at f11, Hyperfocal distance is somewhere around 5 feet (1500mm), so depth of field at this aperture would be from 2 1/2 feet ( 750mm) to infinity, when focused at 5 feet. A good guideline for great depth of field for landscapes is to use the bottom focusing marker in your DSLR viewfinder, (either horizontal, or vertical) as this will focus 1/3 of the way into the distance, (It is on the lower third imaginary Rule of Thirds gridline!) ,as is usually recommended. [ NOTE: Unless your camera has depth of field preview, looking through the viewfinder all will not be in focus, because your lens, until you press the shutter button to make the shot, will be open at full aperture.]
To avoid camera-shake, always use a sturdy tripod. When using lenses equipped with VR/IS (vibration reduction-Nikon/Image stabilisation-Canon), on a tripod you will need to turn off the anti-shake, or lens will still try to counteract vibration that isnt there,, and cause unwanted shake. If, for some reason you cannot use a tripod, use your self as one-
Feet at T-Stance, left hand supporting camera, elbow against ribs
Camera pressed against nose and brow
Right hand also elbow against ribs, index finger on shutter button
Set shooting mode to continuous, and Roll index finger on shutter button - First couple of shots will probably be blurred, but somewhere between 3-4 and 5 you should have a shake-free shot of the scene. ( When using zoom lenses longer than 200mm-I usually set ISO to 400, when hand-holding)
Trap focusing: (Nikon Only)
This is a neat way to use auto focus especially for fast sports/wildlife action.
Custom (pencil) menu:
Autofocus set to AF-S
AF area mode set to single
AE-L/AF-L set to AF ON
Compose your shot and set the focus by aiming the centre focus icon at a definite target at the precise distance you want, (Say a tree branch where a bird is about to land, or on second base where the baseball player's foot will land) and pressing the "AE-L/AF-L" button near the viewfinder. This will focus the lens, let go of AE-L/AF-L button. Turn away,
press and hold the shutter button all the way down. Point camera at pre-focused point when subject approaches, and your camera will take the shot (or shots, if you are in continuous shooting mode.)
Much faster than Human reflexes.
May 2, 2012 20:43:09 #
I don't know Nikon, but does the D300 have focus adjustment for individual lenses? Just in case you have a bad version of the Sigma?
Time to do a focus test...
http://focustestchart.com/focus21.pdf
Time to do a focus test...
http://focustestchart.com/focus21.pdf
May 3, 2012 08:48:47 #
fricciardi wrote:
I just received my new 150mm sigma macro. Been snapping with it a couple of days now and it seems none of my pics are really in focus. Tried manual focus and auto but the pics are soft. Have a Nikon D-300 ; Sigma 150mm micro with image stabalization. Any suggestions what I might be doing wrong or what ideas might make pics better?
Tripod - ISO - DOF
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