I mostly do landscapes and more recently got into birding. My main gear has been Sony A7RV with 24 mm & 50 mm GM primes, along with a 70-200 F4 G.Now that I’m older (75) I find my Sony A7RV is getting heavy for a walk-around camera. I have a 200-600 G for birding which works fine on a tripod but now I find I can’t handhold it, and carrying the tripod + gimbal + big lens is too much for me. .
I recently bought an OM-1 II and 12-40 Pro kit as a travel/walk-around camera and loved it. I sold my Sony 200-600 G thinking I’d use the OM 100-400 II for birding but when I tried it out was disappointed - heavier and softer than I expected. I thought IQ wasn’t any better than my Sony A7RV + 70-200 F4 + TC 1.4, and cropping in on the 61 megapixels. And the weights of the two systems weren’t much different. So I returned the OM 100-400 II.
So now I don’t have a birding lens. I’ve been waiting for the new OM 50-200, which just came out and looks like a fantastic lens but…$3700?
I’m wondering if I’m better off buying a used Sony 100-400 GM, which I can get for about $1600 - half the price of the OM. Both the OM and the Sony take TCs for extra reach.
Sony A7RV + 100-400 GM weighs a bit more than the OM-1 II + 50-200, but is manageable. Both lenses take TCs. OM lens is brighter (2.8 vs 4.5-5.6), newer, probably crisper but…$3700. Sony isn’t as bright, is an older lens but used with a 61 megapixel sensor gives me lots of resolution and room to crop in. OM camera has higher fps but I’ve found the 15 fps on Sony is adequate for my needs.
I have used the a7rV and 200-600 extensively for certain wildlife. It's too slow in FPS and AF for some action subjects and the EVF has the lags, but IQ from the sensor is exemplary as you know.
The problem you will have is that the OM-1 II (common to a micro 4/3 body) has a very small sensor but only about 12% greater linear resolution (3.32µm-OM vs. 3.73µm-a7rV pixel pitch). Therefore a lens of about 534mm is needed on the OM-1 II sensor to produce the same resolution on the subject (pixels per duck). Even if you do have a 500mm lens on the OM the angle of view is very narrow and it is more difficult to frame and track many species.
I don't have any experience with Fuji cameras and lenses, but they have a 40MP camera with 3.02µm pixels in APS-C that you may want to consider.
Maybe the lens you received had an issue. I used to have the V1 of 100-400mm and it was pretty sharp.
Also the om-1 has its advantages. Having used stacked sensors in A1 and Z8, I can't go back to non stacked sensors. The speed and lag free evf advantage is night and day. I would rather get om-1 then a sony A7rV.
ISO 6400. Standard lightroom export, no noise reduction.
Sigma 500mm F5.6 DG DN OS makes more sense to me. You can use it on your Sony. It's less expensive then the OM lens new but you can likely find a used one for even less.
