Minolta 50mm f/1.7 + A900

[mastermind]

Vignetting should occur at the corners of a frame and theoretically shouldn't affect the centre. Not sure about the loss of contrast though. Another possibility is that this lens is actually f1.8 when wide opened instead of f1.7 so it affects the overall exposure.

Here's evidence that should darker centers when wide open in aperture priority and manual exposure. Note, there is a typo in one of the shutter speeds. No prizes if you manage to spot it.

 

[TME]

Looks like some algo in the camera's A priority mode.

 

[TME]

also, look here.

http://kurtmunger.com/minolta_af_50mm_f_1_7_reviewid114.html


seems like vignetting of the lens is the issue here. the F1.7 and F2 crops seemed darker.

If you check Mastermind's test, only the A mode seems to have this problem...

 

[TME]

Oh btw, EXIF indicates that my lens' max aperture is 1/6?!

 

[XkaOnslaught]

how about testing in shutter priority and P mode? maybe its not just A mode thats bugged.

 

[VisionTechnik]

From your posted bear picture the centre frame (bear nose area) is visually same exposure @1.7 as the rest. Try shooting on a clean less distracting wall and the you will see the effect clearly.

 

[TME]

From your posted bear picture the centre frame (bear nose area) is visually same exposure @1.7 as the rest. Try shooting on a clean less distracting wall and the you will see the effect clearly.

The white snout is clearly brighter on the f2 or f/2.8 shot... if you look at Mastermind's shots, the central area is also much darker for f/1.7... it's not just a vignetting effect... in fact, I don't care for simple test shots since they aren't what I would shoot in real life... but the bear (in place of a person) is something that I would use f/1.7 for in real life... and the significant darkening is quite disconcerting... it would mean I have to compensate either software wise or overexpose... a bit unpredictable I might add... also was just wondering if it's an artifact of the lens design or there's something wrong with my lens... seems that most people own the 50mm f/1.7 but don't shoot wide open...

 

[XkaOnslaught]

im still going by my stand that its the lens vignetting problem. nothing to do with the camera at all.

 

[TME]

im still going by my stand that its the lens vignetting problem. nothing to do with the camera at all.

Definitely nothing wrong with the camera... my issue is whether the lens is malfunctioning... or just simply vignetting... it looks quite drastic no? Never seen such severe vignetting especially on a prime...

 

[VisionTechnik]

it's not vignetting, but light fall off due to the lense optical design when wide open.

 

[mastermind]

it's not vignetting, but light fall off due to the lense optical design when wide open.

in other words it's more of a 50mm f1.8 instead of f1.7... no big deal, just need to compensate for it when using it wide open... which is not very often for me.

 

[Galdor]

in other words it's more of a 50mm f1.8 instead of f1.7... no big deal, just need to compensate for it when using it wide open... which is not very often for me.

50mm f1.8 is a DT lens, so you will get vignetting if you mount it on a FF cam.

 

[XkaOnslaught]

50mm f1.8 is a DT lens, so you will get vignetting if you mount it on a FF cam.

thats not what mastermind was refering to lol.

 

[TME]

it's not vignetting, but light fall off due to the lense optical design when wide open.

I see... so it's a flaw in the design... okie lar... can use anyway... just shoot at f/2 lor... hahaha...

 

[MontoyaSG]

the beercan also suffers from vignetting if shot @ F4. probably most of the older minolta glass with smaller front element suffers from such an issue.