Historical Perspective
I often see the N6006 as the older but the little brother of the N90s, especially when I carry both in my camera bag. The N6006 was introduced in 1991. The newer N90s in 1994. The 3-year period spans almost a complete generation of AF technology.
The N6006 represents a classic of the pre-D era of Nikon AF cameras, the Nx00x series, as the FM2n for the all-manual era. Look at it this way: the N6006 has all the new technologies that had been implemented in the then top-of-the-line cameras: it has the AF sensor that can only recognize vertical lines, Nikon's matrix and spot metering, TTL flash technology, etc.
The N90 is the first camera that implements Nikon D-metering technology and the cross-type wide-area AF. The N90 was soon upgraded to N90s for the improved ruggedness and weather-proving. (The F5 dawns a new era of color metering, but it is reported that the AF is quite the same as the N90s, except that the motor in F5 is more powerful to achieve a better performance.)
After the N90s, two new cameras, the N50 and the N70, were introduced, signaling the end of the Nx00x series: the N50 replaces the N4004s, the N70 replaces the N6006, and the N90(s) replaces the N8008(s). In spring 1995, Nikon planned to discontinue the N6006 and dropped its price from $400 to $350. But later that year, the price came back to $400, indicating that Nikon had changed its mind. In irony, one year later, Nikon USA started to offer $35 rebate for the N50 during September to December of 1996, and dropped the price of the N70 by about $100. Later, the rebate was increased to $75 from January 1997, and extended to the N70, indicating that both cameras are going away. And N6006 stays and outlives its successor.
The N90s has been a hot-selling (if not the best-selling) SLR camera ever since its introduction, and remains the technologically most advanced Nikon camera until the F5. The introduction of F5 in June 1996 did not significantly affect the sale of N90s. In a sense, the N90s represents yet another classic of Nikon camera, the pre- color metering era that perfects the D-technology and cross-type wide-area AF. I'd predict that the N90s will also stay for a while even after its successor model is introduced (in 1998?).
Hand-holding:
Both feel very solid and substantial (compared with the N70 and the N50). The N90s is a little heavier, and also felt more rugged. The N6006 appears slimmer. I like the N6006's hand grip a little better, as it has a little more depth. Nikon's handgrip size is definitely better than Canon's I tried (A2: slightly too thin and not enough grip; Rebel: too small; Elan: too squarish).
The battery holder for the N90s seems do not fit well with the opening of the battery chamber, thus my hand often makes little squeaking sound by deforming the chamber, which is a part of the hand grip.
I cannot justify the price for the vertical grip MB-10 ($150) for the N90s.
User Interface:
The layouts on both cameras are very similar: 4 main buttons in the left and the command dial on the right, a few smaller buttons placed nearby. This implies that the layout is kind of "proven classic". I believe the reason that the N70 failed to replace the N6006 is due to its radically different layout, which looks, to many but not all people, too much like an idiot's camera and turns away many serious amateurs whom the camera was designed to target at.
The N90s layout is simpler since fewer features reside in the body, thus eliminates the second function for each button. All settings are done by either 1 button + command dial or 2 buttons.
The illuminated top LCD on N90s is really a good idea. Better if Nikon puts an illumination for the MF-26 LCD panel.
Buttons and Switches: The plastic buttons on the N90s look better than the rubber buttons on N6006. The AF-L button on the N90s is a little too far away from the handgrip.
The AF switch (the "M-S-C" switch) on N90s does not have enough "click" at the "S" position. I often switched directly from M to C with the intention switching only to "S". This is a little bit annoying. The N6006's is a little better, but the switch looks not as nice.
Viewfinder: The viewfinder in the N90s is much much better. In the N90s, the display in viewfinder is dark lettering against illuminated background, which is further brightened by the illumination window on the prism housing. This makes the displays clearly visible under any lighting condition. On the other hand, the viewfinder display on the N6006 is lit lettering against dark background, which tends to be difficult to see in bright lighting such as in an open area in a sunny day.
As for the viewfinder information, I really miss the metering mode display on the N90s, and the AF mode display is not that important for me. Otherwise, both are quite similar.
Camera Back: I use MF-26 multi-control back for N90s. I found that making a setting is quite cumbersome, buttons are generally too small and not responsive. I often have to use my finger nail to press buttons, and it takes too many steps to accomplish a setting. Nikon could have done a better job. I can't justify the price ($250) for the features, since so many features are already built-in the N6006 body. I got mine for $140, a much sensible price.
I can't comment on the MF-25 and the N6006QD model since I've never used them. Neither have I used the data-imprinting feature of MF-26.
Auto Focusing:
I never mind the AF speed since I shot mostly landscapes. My philosophy toward AF is: when there is enough time, use AF. The N6006 is my first AF camera. Maybe this has said enough about the AF of the N6006. I hope that the AF on the N90s could change that.
This philosophy is developed from using the N6006 in several occasions. One was a snow fighting of my friends, they were all running around me about 10 to 15 ft away. The N6006 could not keep up with them. My manual focusing did a much better job. Another occasion is during an MIT commencement. One of my long-time-no-see friends suddenly marched pass me, but the AF was not quick enough to lock on, and since it was in focus-priority, I didn't get any shot at all.
Despite this negative feeling, I often do find that the camera's AF does a better job than my manual focusing, especially with some AF lenses, since my hand simply cannot turn that small amount before I run out of patience. After a long day staring through the viewfinder, as least, the AF is a great relief for my eyes.
The major shortcoming of the AF in the N6006 is that its AF area is too small that a moving object too quickly moves out of the AF area. I haven't put the N90s' AF to a field-test yet. My general feeling is that the AF on the N90s is very responsive. I've mounted the Nikkor AF 80-200 f/2.8 (non-D) on both. This lens is probably the worst nightmare for AF cameras. On the N6006, the AF speed seems helpless, and on the N90s, I am still skeptical.
For the N90s, I haven't really tried on films. I tried the N90s and the 80-200/2.8 combo by following leaves on the ground. It was a windy day, a small group of leaves was rolling/flying on the ground about 10 ft/sec. I stood 15ft away, using C mode and wide area AF to follow them. From the viewfinder, the camera was doing a very good job, and I was quite impressed. I think the speed of N90s' AF system is not that dramatically faster then the N6006. But, the real advantage of the N90s' AF over N6006 is its wide focusing area.
In difficult situations, such as low light without AF assisting light, the N90s' AF system is determined to abandon the AF attempt after it has tried the lens in one direction, returned to the other direction for a full range; that is, a little more than once of the full focusing range. If the camera missed the only time it passes the correct focusing position, it misses it. For the N6006, it just keeps trying back and forth, and may eventually get it right.
Exposure Metering:
I've never used the center-weighted metering in both cameras. Generally, I use spot metering. When in a hurry I use matrix metering.Nikon's matrix metering is quite impressive. In the technical side, the N90s has only theoretically slight improvement over the N6006. The N6006 uses a 5-segment pattern. The N90s uses almost the same pattern but splits the center segment into 4 smaller segments thus makes it an 8-segment pattern, but is heavily inclined to the 5-segment pattern. (See Nikon's explanation for details.) I have yet to observed any significant difference in the results of the two matrix metering systems.
In my opinion, Nikon's matrix metering is very reliable in most situations. In sunny days, I particularly enjoy taking backlit photos, and the exposure is just perfect to my taste. However, if the details in the shadow area in such a sunny day are of interest, they will be underexposed.
I've taken some snow scenes. I tried the old "meter the scene and open up 1-2 stop" trick. I dialed in +1.3 stops of compensation, and then let the camera handle the exposure setting. It turns out that the slides are slightly overexposed by this compensation, even with the scene that is mostly snow with features (such as buildings and trees) take only about 5% of the frame. This means the camera's metering system is doing quite a descent job in such situations if no compensation is dialed in at all.
The spots for the spot metering in both cameras are very small (the N6006 has 3.5 mm diameter circle, the N90s has 3 mm diameter circle, both are less than 1% of the entire image area), and works great for normal to tele lenses. And, best of all, the spot meter works with any lens and any exposure mode.
Flash:
The TTL flash is probably the most significant technical advance represented by electronic cameras that even the die-hard all-manual traditionalists have to envy. And Nikon's TTL flash technology is so far unsurpassed.Using a flash has become so easy these days: simply pop up the flash and shoot. No figuring of the guide number, the distance, and the aperture etc. This makes the variable-aperture zoom an economical choice. And it handles so well that the photo looks like no flash is used at all.
The difference in the flash metering between the N90s and the N6006 is the D- metering technology. This is where the D-metering could really show the advantage. Without the D advantage, I feel the incorporating the idea of matrix metering into flash metering (note: flash metering and the ambient light metering is done by separate meter systems) is good enough for casual party shootings. With the N6006, I've shot hundreds of party shots. Within the reach of the flash, all shots are really great in terms of exposure. (Once I had a badly overexposed photo, taken by forgetting to turn on the "Matrix Balanced Flash" feature and used the standard TTL lash metering.) Surprisingly, the build-in flash for N6006 did not cause any red-eyes in all my shots made within the reach of the flash. (Only one shot , at 135mm FL, subject about 7m away, showed red-eyes, but this is out of the reach and the shot is underexposed anyway.)
With the N90s, I don't know how to compare, since I am already very happy with the N6006's flash metering capability. My major "shoot-out" (;-)) with the N90s+SB- 26 combo is at a friend's wedding, all great. However, I've heard reports that the "3-D Multi-Sensor Matrix Balanced Fill Flash" could cause slight underexposure. But, I always use negative films when I use flash, so that slight underexposure, if true, does not matter much for me: I simply didn't see it.
Other Features:
Canned Program: The vari-program on the N90s is really an insult to photographers. It wastes a precious button space on the camera top. If Nikon insists on putting on such a canned program, they should have switched the button location with the AF area selection button, which is much more important and is currently located awkwardly.
The only canned-program I see feasible for such a high-end camera is a real hyperfocal program, if not Canon's "depth-of-the-field program". Pathetically, the so- called "hyperfocal program" in the N90s is not really a hyperfocal program --- it simply sets a small aperture.
The N6006 is clean on this regard --- no canned program. On the other hand, it has two program modes: P and Pm, and the P mode is really redundant. It seems Nikon is always overdoing something.
Self-Timer: I was surprised to find that the N90s does not provide two-shot self-timer, whereas the N6006 does. The self-timer indicator lights on both camera are too close to the rim of the body, make it hard to see in bright lights, especially when the sun is in the back of the camera, which is unfortunately the most common situation when self-timer is need: group shots. I remedy the situation by placing an empty film canister on the camera top to provide a little shade.
Shutter and Aperture Steps: It is really nice to be able to adjust the shutter in 1/3 stop on N90s. But it takes too long to get to the "bulb" setting. Could have a better way to do this automatically when used with the "long- time exposure" setting. Both cameras only show aperture value in full stops. I don't known why they do not show the continuous step, or, at least in 1/3 stop as the shutter. Maybe the camera is just showing what the lens passes on. No aperture value is shown for MF lens.
DOF preview: Why not an electronic one? (The N6006 does not have DOF preview). But admittedly, the button works better than the lever on FM series. Chances are, you have to recompose after the preview.
Film Rewind: The N90s' film rewind (a 2-button operation) buttons work much easier since both buttons are on the top of the camera. On the N6006, I have to turn the camera over since the buttons are located on the bottom of the camera, a classical location of most manual cameras. When the camera is on the tripod, I have to take it off the tripod first. But why Nikon does not make the camera automatically rewind after the end is reached? BTW, the N6006's film rewind is very slow and noisy.
End-of-Roll: On the N6006, the end-of-roll is indicated in several different ways. The most annoying one is that the camera indicates "End" only when I fully press the shutter to shoot. So far the N90s has been consistent on this regard: either before or after the frame advance. I've heard of reports the N90s would sometimes show an "End" in the middle of the a roll and lock up. I've never had such a problem so far.
Mirror Lock Up: Both do not have, period. Not even the pre-fire mirror lock up, in which the camera flips the mirror at the beginning of a self-timer operation. I can't understand why. The mechanical amateur line FM, which is comparable to the N6006 in my opinion, has the mirror pre-fire lockup, which I prefer over the true mirror lockup.
Noise and Camera Shake: The N6006 is very noisy! Probably the N6006 is the noisiest camera in Nikon line, and the camera shake due to mirror flipping is pretty bad. The N90s is much better. I heard people reporting that the camera shake in N90s is minimal, so small to justify the lack of mirror-lock-up feature in such a pro-body.
I've done the following tests, just for observing the camera shake. For the N6006: Sigma AF 70-300mm f/4.5-5.6 APO at 300mm plus a Vivitar 3X teleconverter (This is 900mm f/16!) on a tripod. With a great patient, I was able to get this combo sharply focused. Tested several shots, all came out terribly blurred. (On a 4"x6" print, sharp images move a distance of 3-10mm!). With N90s: Nikkor 80-200mm f/2.8 at 200mm plus a Kiron 2X teleconverter (So 400mm f/5.6). I only took one shot and it is very clear (I'd blame the lost of sharpness to the optical degradation.) This is not a fair comparison for the two cameras. But I think I have a rough idea. The former has a much longer focal length, but also much lighter, the later is much heavier, and I supported the whole rig on my camera's tripod socket, as neither lens provides tripod support. Maybe I'll also try to 900mm f/16 combo for the N90s some day :-)
Camera Lockup: I used the N6006 for over 2 years. The camera only locks up when battery is exhausted, and the LCD displays exactly what the manual says. If I am lucky, turn off the camera for a few seconds and turn on again, I might manage to get few more shots. Replacing the battery gets everything back to normal.
On the other hand, the N90s has locked up twice on me (use AA alkaline batteries) in a mere few months of courtship. In both cases, the camera did not recognize insufficient power and fired the shutter, but could not finish the shot and left me with a dimmed viewfinder and an "Err" on LCD! Afterwards, the camera still indicated to me "full battery power"! It has wasted several frames of the film. Yuck! (I believe the problem is due to insufficient power in the batteries. Probably the N90s needs quite a large current draw from the battery, which the AA’s lack, although the battery has sufficiently high voltage. In case of such lockups, change the battery and fire the shutter should bring every think back to normal.)
A New Frontier:
The computer interface on the N90s opens a new frontier of camera technology. This opens the access to the inside of the camera. In some sense, it becomes a computer. So far, the most sensible feature is the DataView software, which allowed the user to store and later download the shooting data from the camera. With the N90s, the computer's capacity is quite amazing, and the data in the memory remain even the batteries are taken out.
Actually, this is the main reason lurked me to stretch my budget and buy an N90s. I think this is very useful tool for amateurs mastering exposure and for professional keeping accurate shooting data. However, when I was ready to buy the software, I was informed that a new software, called Photo Secretary, had just been released in February 1997, Nikon said the DateView was obsolete, and the new software should be available imminently. So far I'm still waiting.
Nikon probably has regretted (at least they should) its initial choice to be associated with Sharp by offering AC-2E card which only works with Sharp's electronic organizer, which, alas, has been discontinued by Sharp.