[popo]

For macro use, I never understood the often repeated claims that extension tubes don't degrade image quality like a front mounted "close up filter" does, since you are pushing the lens outside its design intent. Anyway, when using the 50mm f/1.8 II I had noticed you get massive field curvature when you use extension tubes. I didn't pay attention to what other nasties it may or may not have added too, but wouldn't be surprised if there's more.

[Brightcolours]

For macro use, I never understood the often repeated claims that extension tubes don't degrade image quality like a front mounted "close up filter" does, since you are pushing the lens outside its design intent. Anyway, when using the 50mm f/1.8 II I had noticed you get massive field curvature when you use extension tubes. I didn't pay attention to what other nasties it may or may not have added too, but wouldn't be surprised if there's more.

Extension tubes do not degrade "image quality" with well designed lenses. That a 50mm f1.8 is not optimal for certain uses is not the fault of extension tubes... Just the extension tubes show the shortcoming of that particular lens. There are lenses with which you can use extension tubes, with perform just fine. 

[popo]

Extension tubes must degrade quality, I would define as operating the lens outside its design intent. The only question is by how much. If kept in moderation, perhaps it is not significant.

Anyway, I fear we may be drifting off topic here. I still plan to try my proposed configuration to simulate the look of the Petzval once I got some other jobs around the home sorted. Got my box of random lens elements on standby

[Sylvain]

I don't mind the product but the price and the marketing are just too much here.

 

Some PR text was saying it was using "Russian" glass,

it's got this silly build,

Old mechanics,

price is exagerated...

 

Question : how easy would it be to do swirly bokeh in instagram ?