I obtained the Nikon D610 specifically for the better sensitivity of a more modern sensor. I almost went with the 7000 series, but in the end decided the FX format made more sense.
Hmmm what about the D800?
I looked at the D800. Drool did and continues to run down my chin at such a thing. I came to me senses though and decided, for now, it was more than I needed to solve my sports light sensitivity issues.
Hmmm what about the D600?
I heard about the D600 oil spot problems and wasn't pleased with Nikon's handling of the issue. Fortunately, the 610 came out in the nick of time for the 2013 football season and was available at Best Buy with zero interest. This got me off the fence and to the nearest Best Buy stocking the 610. Home I went with one for the big game... THAT NIGHT!
UPGRADE FROM D3000
Our previous camera is the D3000 with two kit lenses. It is a wonderful, albeit somewhat delicate, starter set. Many great pics continue to emerge from this camera. However, light challenged sports photography pushes this camera well beyond reasonable limits. With some hard work, and twiddling of image files, I obtained some good football photos with a later purchased 300mm f/4 lens. Many were published in the local news outlets.
FOOTBALL - ENTER THE D610
Into this situation I put the 610 with instant and amazing results. The sensor sensitivity is astounding. The ISO settings beyond the top end, H+, are, of course, noisy, but provide quite usable images with quick action-stopping shutter speeds. Eureka. Quite suddenly sensor sensitivity is no longer a worry on the football field. Understand I went from the worst case CCD sensor D3000 to a modern CMOS FX sensor so my wow factor incorporates a very very wide swing in technology. YMMV.
Recall this D610 went from box to field in less than 11 hours after a good battery charge at work. I literally entered the field with a camera I had never touched before. I fumbled with the menus and settings. Sports mode works pretty well and lots of good images came forth. Sometimes I like to set things manually for the field lighting and so I did with this new camera. That worked quite well, but I could not, for the life of me, turn off the autofocus assist light. I felt like, and looked like, a complete dork with the autofocus light flashing despite the big 300mm lens. I didn't have time to fuss with it so I simply continued to take shots and good ones at that. Later I finally researched the manual to find the setting to turn off that light.
The point to take away from this is not every option is obvious in the menu system when you are in a rush. Don't fret though... gadget hounds, like you all, well learn the menus quick enough.
BASKETBALL AND DX LENSES
Later work for basketball was a bit more difficult. Gyms vary in brightness (as do football fields), but the real problem is my faster 300mm lens, despite the larger image in the FX sensor, was too much magnification for many of the circumstances. Thus, I fell back to the telezoom from the D3000 starter kit. The 610 handles DX lenses just fine by reducing the field of view automatically (I think you can force it to use the whole sensor with DX lenses if you want). This slower lens combined with the incredible ISO sensitivity solved the problem of how to make motion freezing basketball images with "good enough" color, etc. DX lenses on FX cameras are not something you really want to live with and I've ordered a Nikon 80-200mm f/2.8 AFD FX lens (a bargain lens - check it out) to address this for spring baseball season and beyond. That said, I very much appreciate the D610 providing some way to use just about any Nikon lens even if a compromise.
The cycle rate is quick. Turning a knob to set single fire, slow continuous or fast continuous is very nice and a welcome feature.
The D610 focus points are, apparently, just like the 70XX DX and are crowded in the middle of the FX frame. This is a little weird, but I've gotten use to it.
Autofocus can be a little off at times, but I have more good images than bad so the scorecard of the D610 is in good shape. The D3000 focus system works a little better IMO.
Yes this camera has video capability. It works with both FX and DX lenses. Video files for DX are smaller, I think, than with FX. Regardless, this thing will choke your card with amazingly large HD videos with the flip of a few camera settings. I didn't really care about this until I used it a time or two. It's nice, but isn't why I bought the camera.
An observation while videoing is the auto focus doesn't seem to work like you've likely come to know in a real video camera. I press the shutter button to initiate a refocus. It's clumsy. There is likely a better method I haven't found yet to take better videos.
Video straight to digital files is a great thing, but the D610 doesn't make me want to stop using my 2002 vintage Sony mini-DV SD video camera which functions much better. The D610 is clearly designed for taking pictures with video as a nice side capability.
I've nothing bad to say about the D610 battery life. I'll be ordering a spare battery simply because I should, but the one that came with the camera easily yields 700+ images with a big heavy auto-focus zoom. I do wish the D3000 and D610 would use the same battery, but that's life and I understand why they differ.
I specifically avoid CF cards and I don't regret it one bit. I like SD and the D610 supports two with a variety of redundancy modes. I'm quite pleased with this arrangement.
GOOD, BUT NOT GREAT VALUE
Laying down the coin for something like this can cause one to pause. The upgrade to a modern FX sensor has solved my particular ISO issues. A D7100 DX or equiv. would have likely done so as well and at quite a bit less cost. I just had to have FX so that's my own fault.
Getting a perfect score from me requires a... perfect score. The D610 comes close. The small DX focusing system on an FX sensor is a bit odd. Given the D600 goes for $1500 or so suggests the $2000 price tag for a D610 may be a bit high. I see the price came down to $1900 so perhaps we are seeing a reality check in play. If this FX camera had an FX focusing system, I'd say five stars. I bought it though so I guess it is worth it to me. I admit part of me simply wanted an FX to say I have an FX. Sigh.
The D610 is a good camera with great sensitivity that I'm glad to own. Time will tell about it's long term ruggedness. Despite the few issues, for the moment it is doing exactly what I need it to do... and I can't ask much more from my equipment.