What is "Field Curvative"?

Field curvature means the spherical shape of the focus field. Theoratically, we would assume that the depth of field (the sharpness zone dependent on the object magnification and focus distance) starts at some focus distance x in front of an focused object and ends at some distance y behind. The difference between x and y is called the depth-of-field.

In the real life there's no perfection though and the focus field can be rather distorted (as opposed to flat) with consequences for the depth of field. For sure this isn't overly field relevant but at the image borders the focus field turns inwards (towards you). In infinity focus situation this may cause some focus blur for distant object located at the edges of the image field. It is also relevant for flat objects.



Exaggerated sample :

nikon micro-nikkor AF-S 60mm f/2.8G ED-IF NANO

Nikon Micro-Nikkor AF-S 60 mm f/2.8G ED IF Nano (2008 Release)

FACTORY SPECIFICATIONS

Focal Length : This is a FX format lens, so you can both use them on typical SLR 35 mm cameras and D-SLRs. It is compatible with D40, D40x and D60.
Aperture: f/2.8 . Nine-bladed rounded diaphragm stopping down to f/32
Optics: 12 elements in 9 groups. That includes one ED glass element (shown in yellow) and two aspherical elements shown in blue.

Closest Focus: 18.5 cm(0r 7.2 inches)
Macro Ratio: 1:1 (real Micro lens)
Filter size: 62mm
Accesories: Lens rear/front caps, Barrel-shaped HB-42 Bayonet Lens Hood Supplied
Dimensions: 73 mm(2.9") diameter. Extension from lens flange (length excluding rear mount extension) is 89 mm (3.5").
Weight: 425 grams (15 oz)

MY REVIEW ABOUT THIS LENS
The Micro-Nikkor 60mm f/2.8G Nano is extereme sharp and silent lens. Build quality is excellent. Lens glass quality is very high and together with Extra-low Dispertion coating and Nano coating, all flares ang ghosts are successfully eleminated. According to IMATEST results, barrel distortion level is only 0,06% ,could be called as "DISTORTION FREE". Vignetting is seen moderately ay f/2.8, but after that, it is not field relevant. MTF Resolution results are very good, even excellent starting from widest aperture up to f/11. The results seen at f/22 and f/32 are quite soft, which is not a surprise. Chromatic Aberrations are higher than expected, could be called as a shame for a brand new lens in the market with Crystal Nano coating. CA's are 1.6 pixel down to 1 pixel respectively with aperturesettings starting from f/2.8 (1 pixel is limit)


It is a relatively cheap lens and not so heavy that can be also used for candid photography.

But, if you are shooting products not smaller than 20-30 cms, this lens is an excellent macro for you. I have faced some problems to shoot mugs with my 105mm VR as i need to move back to fit the mug in the frame.



PAY ATTENTION :
- This lens' weakest point is Chromatic Aberrations (blue/purple color shadows at harsh contrast transitions) which are around 1,4-1,0 pixel .

VERDICT : Very high sharpness (i was expecting better results, but it does not mean bad ofcourse) and macro abilities with very fast focusing makes this lens a desirable high budget fast macro lens in the market. But over limit CA's (could be deleted by new softwares and Nikon's built in processors) does not fit this prime lens. Recommended (8/10)

nikon micro-nikkor AF 200mm f/4.0D ED-IF

nikon Micro-Nikkor AF 200 mm f/4.0D ED IF (1993 Release)

FACTORY SPECIFICATIONS

Focal Length : This is a FX format lens, so you can both use them on typical Film SLR 35 mm cameras and D-SLRs. (fits all of digital nikon models except D40 , D40x and D60 )
Aperture: f/4.0 . Nine-bladed rounded diaphragm stopping down to f/32
Optics: 13 elements in 8 groups. That includes two ED glass elements (shown in yellow below).

Closest Focus: 50 cm(0r 20 inches)
Macro Ratio: 1:1 (real Micro lens)
Filter size: 62mm
Accesories: Lens rear/front caps, Barrel-shaped screw-in type HN-30 Bayonet Lens Hood (optional). CL-45 flexible lens pouch supplied
Dimensions: 76 mm(3") diameter. Extension from lens flange (length excluding rear mount extension) is 193 mm (7.7").
Weight: 1.190 grams (42.3 oz)

MY REVIEW ABOUT THIS LENS
The Micro-Nikkor 200mm f/4D is very sharp lens with a very good build quality. According to IMATEST results, barrel distortion level is only 0,05% , not even negligible in lab conditions. Vignetting is almost non-exsistant, even at widest aperture setting of f/4.0.

MTF Resolution results are excellent (at f/4 to f/11). Chromatic Aberrations are increadibly low, even at lab. This lens shows no signs of lateral CA's. Exceptionally rare characteristics.
The focusing speed iseems very slow, if you do not switch off -very handy- "full" switch on the body, which starts from 0,50m to infinity. After "limit" switch, focusing become regular. There is no Silent Wave Motor on this lens. It uses old style -loud and slow- focusing motor.

For makro photographers, this lens is "the lens" you are looking for.

Frankly Suggestion : If your budget is not enough to buy this lens, my personal suggestion is to buy a Sigma 150mm f/2.8 Macro lens for only-macro-obsessed enthusiasts.

PAY ATTENTION :
- This lens' weakest point is being heavy and slow/loud focusing.
- Relatively high price and 1993 release pushes me twice before purchasing this lens. (But now I own it- February 2010). I believe that nikon will announce a new nikon 200mm nikkor-micro f/4G VR IF ED Nano in few years. But it will be a "G"elded lens and more plastic and Made in Thailand :( ... So, before being a classic, i recommend you own one if you can afford...

VERDICT : It is an expensive and a heavy lens but the build quality, sharpness and almost no CA's are excellent. This lens is indispensible for "more micro" searchers. Highly Recommended (9/10)

nikon mount budget sigma super telephoto zoom lenses

There are two questions:

1) What is your purpose of buying a super telephoto zoom?
2) What is your budget?

If you want to shoot professionally birds or F1 racing cars, a zoom lens will not serves you appropiately. If you are shooting at hand, you need a lot of light and a fast aperture. Please check my comments for budget sigma lenses found in the market..


Sigma 50-500 mm f/4.0-6.3 EX DG HSM
1160 US$ > 1840 gr > 20 optics> optical quality 6,5
Pros:
Wide range covering from 50mm to 500mm
Cheap
Recommended for general purpose and tripod use

Cons:
Heavy
Very Slow
Not recommended for fast moving object shooting
Not good for handheld usage

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Sigma 100-300 mm f/4 EX DG HSM APO
1200 US$ > 1440 gr > 16 optics> optical quality 9,5

Pros:
Very fast aperture
Excellent quality of optics
Could be used at handheld
Recommended for sports and wildlife shooting
HIGHLY RECOMMENDED LENS

Cons:
Telephoto finishes at 300mm (could be used with 1.4x teleconverter > 420mm)

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Sigma 150-500 mm f/5.0-6.3 OS HSM
979 US$ > 1910 gr > 21 optics> optical quality 6,5

Pros:
Telephoto upto 500mm
OS (Optical Stabilisation) - Sigma's VR
Not so expensive for a 500mm telephoto zoom with OS

Cons:
Very heavy (Because of OS)
Very Slow Aperture
Not recommended for fast moving object shooting like race cars and birds
Not so good for handheld although OS gives 2 stops advantage
Not so sharp optics

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Sigma 170-500 mm f/5.0-6.3 APO HSM

769 US$ > 1345 gr > 13 optics > optical quality 7,5

Pros:
Only for ultra long telephoto purposes
Very cheap
Lighter than its rivals
Reasonable optics

Cons:
Very Slow Aperture
Not recommended for fast moving object shooting , only tripod usage recommended
Not good for handheld usage

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Sigma 120-400 mm f/4.5-5.6 APO DG OS HSM
849 US$ > 1750 gr > 21 optics> optical quality 7

Pros:
OS (Optical Stabilisation) - Sigma's VR
Not so expensive for a 400mm telephoto zoom with OS

Cons:
Only upto 400mm
Quite heavy (Because of OS)
Very Slow Aperture
Not recommended for fast moving object shooting like race cars and birds
Not so good for handheld although OS gives 2 stops advantage

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Sigma 135-400 mm f/4.5-5.6 APO DG
NA as brand new > 1245 gr > 13 optics> optical quality 7

Pros:
Not so expensive for a 400mm telephoto zoom with OS
Light, can be used handheld under strong light

Cons:
Only upto 400mm
Quite loudy because of old style focus motor
Very Slow Aperture
Not recommended for fast moving object shooting like race cars and birds
Will be replaced with a new model soon


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Sigma 80-400 mm f/4.5-5.6 EX APO DG OS
999US$ > 1750 gr > 20 optics> optical quality 7,5

Pros:
OS (Optical Stabilisation)
Not so expensive for a 400mm telephoto zoom with OS
Wide covering range

Cons:
Only upto 400mm
Very heavy (Because of OS)
Very Slow Aperture
Not recommended for fast moving object shooting like race cars and birds
Not so good for handheld although OS gives 2 stops advantage
Loud focusing motor