So I totally get the struggle... I remember when I first got my a7R IV and realized my bank account was basically crying lol. I spent so much on the body that I really had to hunt for a deal on glass! Respectfully, I'd consider another option if youre worried about budget. While the Sigma mentioned earlier is fantastic, you can get insane sharpness for way less: * Laowa 100mm f/2.8 2X Ultra Macro APO for Sony E-mount - Tbh, this lens is around $450 and the 2:1 magnification is literally a game changer for insects!
* Tokina FiRIN 100mm f/2.8 FE Macro for Sony E - Usually around $350 and it's highkey sharp enough for that 61MP sensor. Anyway, I learned the hard way that for insect macro, I'm almost always using manual focus anyway... so spending $1k+ for AF felt kinda pointless. Value is king!! peace 👍

In my experience, picking glass for that Sony Alpha a7R IV Mirrorless Camera is actually kinda stressful cuz that sensor shows EVERYTHING. Honestly, I would suggest the Sigma 105mm f/2.8 DG DN Macro Art for Sony E-mount over the Sony FE 90mm f/2.8 Macro G OSS. I tried both and the Sigma is basically way sharper... it literally resolves those tiny details on bug wings better than my old lenses ever did. But yeah, a quick tip: you gotta be CAREFUL with your aperture. Even with the best lens, once you hit f/11, diffraction starts kicking in and ur gonna lose that 61MP crispness. Idk, maybe try focus stacking instead of just stopping down? It’s a bit more work but it's way safer for your images. The Sony is a decent option if you need the OSS, but the Sigma works better for resolution. gl!

Facts.

In my experience, feeding that 61MP sensor is a whole different ballgame. I've used the Sony FE 90mm f/2.8 Macro G OSS a ton, and it's a solid workhorse, but honestly, it starts showing its age when youre pixel peeping on the a7R IV. If you're serious about insect macro and want to avoid that 'mushy' look at smaller apertures, you gotta be careful with diffraction. It hits pretty early on high-res bodies, usually around f/8... kinda sucks tbh. If you dont mind manual focus (better for bugs anyway lol), the Voigtlander MACRO APO-LANTHAR 110mm f/2.5 Lens for Sony E is lowkey the sharpest thing I've ever used. Its APO design basically kills color fringing, which is HUGE for fine details. But yeah, focus stacking is definitely gonna be your best friend to keep that *bite* on the sensor—basically just take multiple shots at f/5.6 and merge 'em. gl!

tbh i've been doing a lot of reading lately because i'm also worried about that 61MP sensor showing every little flaw. from what i can see looking at the market research and recent comparisons: 1. Honestly, you should just look at the high-end third-party brands like Tamron. They've *realy* stepped up their game lately and most of their modern glass is basically designed to handle these huge files now without costing a fortune.
2. If you want the most reliable autofocus, going with any first-party lens from the manufacturer is usually the safest bet. It might cost more, but the way they talk to the camera body just seems smoother for tracking moving insects compared to others.
3. Basically, just make sure whatever brand you pick, you look for their "premium" labels. The budget lines might struggle with that resolution, but the top-tier stuff from almost any major brand is gonna be *insanely* sharp on an a7R IV. Does anyone know if the third-party ones still have slower focus? I'm still learning how all this works lol, but it seems like a big factor.

Late to the party but if youre chasing every single pixel on that 61mp sensor you might wanna look past the usual suspects. I've been shooting with the a7R IV for a few years and most glass just crumbles when you start cropping in. If you dont mind manual focus—which lets be real, for serious insect macro you usually want that anyway—the Voigtlander MACRO APO-LANTHAR 110mm f/2.5 Sony E is basically the gold standard for resolution. It is an apochromatic design so you get zero color fringing which is a life saver when you have that much detail to look at. If you need autofocus for moving bugs tho, check out the Tamron 90mm f/2.8 Di III MACRO VXD Sony E-mount. It came out pretty recently and was specifically designed to handle these newer high-res sensors better than the older Sony G. Its super light compared to the Sigma Art and the bokeh is buttery smooth. Just watch your apertures... diffraction starts killing your sharpness around f/8 or f/9 on that body so dont think stopping down to f/22 is gonna save your depth of field without making everything look mushy. Better to focus stack if the bug stays still long enough.

Would love to know this too