Minolta 5400 Scanner Lens and Laowa 25mm f/2.8 Comparison

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Macrero
Posts: 1170
Joined: Thu Sep 01, 2011 8:17 am
Location: Valladolid , Spain

Post by Macrero »

Pau,

I did more tests I don't keep, and to me, without a diaphragm there is less resolution/detail resolved, worse coverage (as is to be expected) and a pretty awful glare/fogginess.

100% center crops after adjusting levels.

Without diaphragm:

https://images2.imgbox.com/0e/da/vrczffq6_o.jpg

With diaphragm:

https://images2.imgbox.com/a2/1c/KWI8O3Rd_o.jpg

Also, coverage without diaphragm is worse at 2.1X than at 1.25X with diaphragm. At around 1X it is much worse.

But hey, I don't mind taking the lens back to the repair shop and get it with the diaphragm removed again :D When I have some free time I will make a proper comparison.

- Macrero
https://500px.com/macrero - Amateurs worry about equipment, Pros worry about money, Masters worry about Light

Pau
Site Admin
Posts: 6054
Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Post by Pau »

I wouldn't dismount the lens again, the glare shown is enough argument against doing it.

An interesting test will be to shoot the same subject at the same magnification with the stop in its place (I still see higher resolution at the subject in the higher magnification image, although comparing different magnifications is not a fair test)
Pau

Macrero
Posts: 1170
Joined: Thu Sep 01, 2011 8:17 am
Location: Valladolid , Spain

Post by Macrero »

Will do a test matching the M of the one without diaphragm. That will be a fair comparison.
https://500px.com/macrero - Amateurs worry about equipment, Pros worry about money, Masters worry about Light

Macrero
Posts: 1170
Joined: Thu Sep 01, 2011 8:17 am
Location: Valladolid , Spain

Post by Macrero »

Here is the test with the lens with the diaphragm re-inserted:

https://images2.imgbox.com/a9/a4/LmzsJbfj_o.jpg

100% crop without diaphragm:

https://images2.imgbox.com/90/4b/K0JBY3qG_o.jpg

100% crop with:

https://images2.imgbox.com/22/0e/eKoivKa1_o.jpg

I think it is pretty clear that designers have done well with putting that tiny ring between elements :P Wider aperture not necessarily translates to higher resolution. Not to mention the horrible glare and worse coverage.
https://500px.com/macrero - Amateurs worry about equipment, Pros worry about money, Masters worry about Light

Pau
Site Admin
Posts: 6054
Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Post by Pau »

Thank you for performing the test.
Now it's clear that the image with the stop has not only more contrast but also more resolution.
Pau

Macrero
Posts: 1170
Joined: Thu Sep 01, 2011 8:17 am
Location: Valladolid , Spain

Post by Macrero »

My pleasure. I was curious to see how removing the diaphragm would affect performance. It was logical to expect a negative impact, although I had the "remote hope" of getting a higher resolution. I had no luck, but hey, at least I tried...
https://500px.com/macrero - Amateurs worry about equipment, Pros worry about money, Masters worry about Light

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