Budget macro lens with minimal field curvature?

[Fandyus]

I have been looking to find out if there are any cheapo macro lenses with minimal field curvature. I'm not really looking to buy one right now, just so that I know what to be on the lookout for. I like taking macros of flat planes, textures, perhaps in the future even developed film. Unfortunately, using extension tubes with normal lenses has proved bad for this, as those lenses are not optimized and the corners are usually soft at macro magnifications, even stopped down.
I don't really mind any other optical faults. I really just want a lens that would have little to no field curvature at 1:1 or so, could even be stopped down, f/5.6 or f/8 max, after that I would lose detail to diffraction.
I have a Sony a6000 and a Canon 6D. I'd be fine with a good suggestion for either.
I have considered the 7artisans 60mm F2.8, but I really don't know about any reviewers that test corner sharpness at macro levels. If you know of any or you have any recommendations yourself, please share.
Thanks!

[Himself]

By design any macro lens has a flat field.
Or it's advertised to have one.
Then it's a matter of parallelism between the subject and the lens.

[visualopsins]

M42 Asahi Super-Multi-Coated BELLOWS-TAKUMAR 1:4 / 100 (bellows needed to focus)
M42 Asahi Super-Multi-Coated MACRO-TAKUMAR 1:4 / 100 (max. 1:2, or use bellows/extension tube for 1:1 or better)

Th original M42 Macro-Takumar 1:4 / 50 (1:1 without use of bellows or tubes)

(We have seen faster macro lenses have more field curvature, likely due to dual-usage as portrait lenses http://forum.mflenses.com/zuiko-90mm-f-2-macro-vs-tokina-at-x-90mm-f-2-5-macro-t83417.html )

[cooltouch]

Based on recent eBay searches, one of the best deals to be had on one of the best macro lenses ever made, is for the Nikon 55mm f/3.5. I own three of these lenses (all pre-AI), and I'd be willing to part with one of them for $50. They all have varying amounts of wear, but the glass is perfect. But, by all means, check out the eBay listings first.

The Nikon 55/3.5 has a very flat field. I've taken thousands of slide duplicates with mine, and I used it to dupe slides because of its flat field.

[caspert79]

[eggplant]

Reversed enlarger lens.

<£35

http://extreme-macro.co.uk/reversed-enlarger-lenses/

My Minolta E.Rokkor 75mm f4.5, not reversed, at up to 1:1, for flat document work. On APS-C it's great to the edges.

It was 99p. For what it's worth these were made in the 80s, not all cheap enlarger lenses you can find are as recent though.

EDIT: My camera is an a6000, the same as yours.

The lens diagrams here were done with this lens and my a6000- https://www.flickr.com/gp/194408730@N08/74M61E

Ignore uneven lighting and document flatness issues.

I tried reversed 50mm lenses and even 50mm lenses in tandem, they absolutely suck for flat field even stopped down to f11, only a small center region is OK. This is great wide open at f4.5, I pretty much gain depth of field stopping down.


The options above are great but exponentially more expensive than even the better Schneider enlarger lenses.

[cooltouch]

[visualopsins]

[alex ph]

+1 for enlarger lenses, might be the cheapest option for this use.

[stevemark]

[Fandyus]

Thank you everyone for the recommendations so far.
I happen to own a Meopta Anaret 30mm f/4.5, my Sony a6000 is currently in transit as I'm having it converted to full spectrum but I'll definitely see about mounting it in reverse.

[kypfer]

My Russian LZOS 50mm f/2.8 N-61L/Z (not N-61L/D) works for me and wasn't expensive … when I want something a bit longer the Tamron Adaptall-2 90mm f/2.5 is hard to beat, but they've managed to retain their value over the years!

[eggplant]

Also, for consideration- I was amazed at this-

Stacking two low-cost enlarger lenses (coupling them in a 'tandem' configuration - https://scientificimaging.com/knowledge-base/tandem-lens-macroscope-configuration/)

out-performed a typical 1x macro lens at 1x:

https://www.closeuphotography.com/1x-low-cost-lens-test/2019/1/7/1x-lens-test-high-performance-and-low-cost

It's performing better at a faster effective aperture too, which is the bonus of this configuration.

Yes, only one 1x macro lens tested (Tamron AF 90mm f/2.8 SP Di) but its representative of the old suggestions mentioned here...

[martinsmith99]

+1 on enlarger lenses.

[D1N0]

Inverted tessar 50mm lens or on tubes (poor man's macro)

This is on a 25mm tube:
You can see the focus plain is pretty straight.

[jamaeolus]

Isn't part of the edge issues in lenses not attributable to field curvature but manufacturing?

[-rageQuit-]

If cheapness is the primary concern, I'd consider:
the Cosina / Vivitar AF 100mm f/3.5 Macro
(available under other brand-names as well, but I wouldn't know their prevalence in continental Europe (eg. Phoenix?))

UK auction ending price is approx 40GBP.
Comes in EF mount, potentially making control on your Canon camera easier and, depending on the adapter, the Sony also.
Look out for copies that come with the matched 1:1 screw-in adapter - otherwise it does 1:2 on it's own.

[nrparsons]

The Sigma 50mm f/2.8 Macro has good reviews and can be had for around $150. Even better is the Sigma 50mm f/2.8 EX DG, but it is at least $100 more. I have the plain vanilla version. I haven't used it much, so I can't speak to its flat-field capabilities, but it was a budget lens to me.