Xjyuk

I currently have a Nikon D70 that I purchased back when it was the "bees knees" and it has served me well for a long time. I get some great shots from it, but I really struggle in low-light situations. I hesitate to push it past 1000 ISO due to excessive graininess, but then need to fight with excessive flash (the cave effect), low shutter speeds, or unforgiving DoF. I think it may be time to upgrade...on a budget, of course.

I've been considering a D700, since it seems to be the cheapest way to upgrade to a solid camera with a larger sensor (and compatible lens mount). I feel like this will help me where I need it most; low-noise low-light imagery. However, even used it's a big purchase for me. Especially since my zoom lens is DX so I'll need a new one. I'm having trouble justifying the purchase unless I can really be sure of a substantial improvement.

I have seen a lot of comparisons online from automated camera database sites. What I'd really like to know is how these two cameras compare in sharpness and noise in low-light situations, though. This would be best seen through comparison photos (photos of the same subject taken with both cameras), especially with comparison crops, but surprisingly Google has failed to show me any...I guess because the D70 was more often compared to the D7000.

Can someone provide comparison photos with full resolution crops between these two cameras?

This may end up being closed as 'opinion-based' but before that, my own opinion.

Unless you're picking it up for pence, I wouldn't trade up from a DX 6mp camera from 2004 to a 12mp camera from 2008.

10 years is a long time in electronics.

I'd be looking at a 24mp camera - the 3xxx or 5xxx - where focus speed & low light performance will literally be years ahead.

Both also DX so you can bring your lenses with you.

In my opinion, the best tool to do such a comparison is DpReview.com. Here is a link for the tool, you need to invest some time to find similar cameras.

https://www.dpreview.com/reviews/nikon-d7500-review-speed-and-capability/8

If you want to see the specs, use this other comparison page

https://www.dpreview.com/products/compare/cameras

The problem is that the D70 is too old for these tests. But you probably can dig in to find the old comparison test page.

For your specific case, you need to take into account if you really need or want to go for a larger sensor, because any DX lens you have will not be usable on an FX format.

If you only have one DX lens, there is not much to lose there.

But I would not go for an oldie full frame camera, in my opinion, a newer DX camera will have better features. You probably do not think you want or need video, or better battery performance or more megapixels.

I love Nikon, my first camera was an FM2. But as you seem not having a lot of already purchased Nikon gear (lenses) you might consider other brands to suit your specific needs. Canon, Sony, Fuji?

Reading the comments you posted, probably the real issue is low light performance. Remember that you can go for a faster lens, a noise reduction software. But in any case, still, a newer sensor will perform better in low light than an old one.

In some other cases, having a 24 Mpx image with good enough low noise will be a heck more smooth if you resample to your mentioned 6Mpx. This way, with a 24Mpx sensor you can push your maximum ISO you are normally willing to accept.