My Tech-Related Photography Posts
- Digital Image Color Spaces
- Online Exif (Image Data) Viewer
- Adobe Lightroom 1.x Resources
- Jeffrey's Lightroom Configuration Manager
- Adobe Lightroom Custom Metadata-Viewer Presets
- Jeffrey's Autofocus Test Chart
- Photoshop CS2 Calendar-Template-Building Script
- A Qualitative Analysis of NEF Compression
- NEF, Color Space Settings, and Embedded JPGs
- Tripod Stability Tests, Part I
- Timing a Transcend 80x 4GB Compact Flash card
with a Nikon D200 - Digital Camera “White Balance”
- Maximum Aperture of the Nikon 18-200mm
Throughout its Zoom Range
more...
The only lens I own for my Nikon D200 is a Nikon “AF-S DX VR Zoom-Nikkor ED 18-200m F3.5-5.6G(IF),” also known as “the 18-200mm.”
I really love it as a fantastic all-around lens, but at f/3.5-5.6, I find that it is sometimes a bit slow (that is, it doesn't let in enough light for me to use a fast-enough shutter speed). So, I've been thinking of getting a faster (allows in more light) lens for use in lower-light situations.
Because of its “18-200mm f/3.5-5.6” name, I know that my lens is f/3.5 at 18mm, and f/5.6 at 200mm, but what is it in between? Without knowing, it's hard to compare how much faster a different lens might be. For example, how much faster is Nikon's f/1.4 50mm lens than the 18-200mm at 50mm?
So, I set the camera to wide open and turned on the high-speed continuous drive, and held down the shutter while sweeping the lens through its full range of focal lengths. I then plucked the data from the MakerNotes in each image and plotted it.
I see that the 18-200mm is f/4.6 at 50mm, which is just about 1/3rd stop slower than f/4.0 (which is 3 stops slower than f/1.4 — if you need them, here are two primers on f-stops).
So, compared to the 50mm f/1.4, my lens is 31/3 stops slower, which is a lot. That's the difference between a shot at 1/15th of a second, in which even mild subject movement is blurry, and one at a much more snappy 1/160th of a second.
I'm thinking of something like Nikon's 17-55mm F2.8, but can't see shelling out $2,000 for only a 2/3rd gain at 18mm and a 11/3rd gain at 55mm.
Isn't there at least an f/2 (or better) in this range?
UPDATE: I ended up getting the 17-55 f/2.8 and love it.
Technical Notes
The main graph above is logarithmic on its Y (f-stop) axis, and linear on its X (focal-length) axis. Perhaps not surprising, the plot appears as a straight line when the X axis is also logarithmic.
The graph on the right shows the same data in a log/log plot.
Despite the 18-200mm's smooth zoom throughout its range, the Exif data and the MakerNotes data have only a limited number of points along that range that they'll report, and oddly, the two sets of data are slightly different. I've shown the MakerNotes' data in the graphs.
The full data from both are shown in the tables below.
From the MakerNotes Data
| 18.3mm | f/3.6 | 27.5mm | f/4.0 | 38.9mm | f/4.4 | 56.6mm | f/4.8 | 95.1mm | f/5.3 |
| 20.0mm | f/3.6 | 28.3mm | f/4.0 | 40.0mm | f/4.4 | 59.9mm | f/4.9 | 106.8mm | f/5.5 |
| 20.6mm | f/3.7 | 29.1mm | f/4.0 | 42.4mm | f/4.5 | 63.5mm | f/4.9 | 113.1mm | f/5.5 |
| 21.8mm | f/3.7 | 30.8mm | f/4.1 | 43.6mm | f/4.5 | 65.4mm | f/5.0 | 119.9mm | f/5.5 |
| 22.4mm | f/3.8 | 31.7mm | f/4.1 | 46.2mm | f/4.6 | 71.3mm | f/5.0 | 130.7mm | f/5.5 |
| 23.8mm | f/3.8 | 32.7mm | f/4.1 | 47.6mm | f/4.6 | 75.5mm | f/5.0 | 138.5mm | f/5.7 |
| 24.5mm | f/3.9 | 33.6mm | f/4.2 | 50.4mm | f/4.6 | 80.0mm | f/5.2 | 151.0mm | f/5.7 |
| 25.9mm | f/3.9 | 35.6mm | f/4.2 | 51.9mm | f/4.8 | 82.3mm | f/5.2 | 169.5mm | f/5.7 |
| 26.7mm | f/3.9 | 36.7mm | f/4.4 | 55.0mm | f/4.8 | 89.8mm | f/5.2 | 201.6mm | f/5.8 |
From the EXIF Data
| 18mm | f/3.5 | 31mm | f/4.0 | 44mm | f/4.5 | 62mm | f/4.8 | 105mm | f/5.3 |
| 20mm | f/3.5 | 32mm | f/4.0 | 46mm | f/4.5 | 65mm | f/4.8 | 112mm | f/5.3 |
| 22mm | f/3.8 | 34mm | f/4.2 | 48mm | f/4.5 | 70mm | f/4.8 | 120mm | f/5.3 |
| 24mm | f/3.8 | 35mm | f/4.2 | 50mm | f/4.8 | 75mm | f/5.0 | 130mm | f/5.3 |
| 26mm | f/3.8 | 36mm | f/4.2 | 52mm | f/4.8 | 80mm | f/5.0 | 135mm | f/5.6 |
| 27mm | f/3.8 | 38mm | f/4.2 | 55mm | f/4.8 | 82mm | f/5.0 | 150mm | f/5.6 |
| 28mm | f/4.0 | 40mm | f/4.2 | 56mm | f/4.8 | 90mm | f/5.0 | 170mm | f/5.6 |
| 29mm | f/4.0 | 42mm | f/4.5 | 60mm | f/4.8 | 95mm | f/5.3 | 200mm | f/5.6 |
It’s interesting, Jeffrey, thanks.
I used this lens yesterday in a low light situation (Q+A after a film presentation in a Museum setting) and found the VR really useful — more so that I expected.
While I like this lens as a walk-around — especially in good light — I too am seriously considering a faster zoom in the wide end of the range (I already have the 70-200VR).
At this time I have no desire to get a larger zoom than than the “something to 70″ that came with my D70, but I also had a need for a faster lens (for indoor photography at church events). I purchased the Nikkor f/1.8 50mm lens (very reasonably priced at less than $150) and so far initial tests show that it is indeed noticably faster.
I may try the same tests on my 12-24 wide angle. That sounds like a fun weekend project.
My 18-200 VR arrived with focusing problems, so I’ve sent it to Nikon for repair. What I’ve found the greatest issue with this lens is the HUGE depth-of-field (a result of comparatively high F-numbers). Since shooting with this lens wide open won’t yield the best of results, stepping further down from F3.5 @ 18mm to say F5.6 will give you a tremendous depth-of-field (whether this is a problem or not depends of your subject, but not having a choice is annoying). Apart from that, shutter speeds are (in most situations) counter-acted by VR, and I’ve found this lens to be good fun in most relaxed situations. If under pressure - such as at a wedding - my guess is that you’d be better off with the 12-24. If you’ve got the money…