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24mm lens comparison (Minolta/Pentax/Tokina)
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PostPosted: Mon Feb 13, 2017 5:31 pm    Post subject: 24mm lens comparison (Minolta/Pentax/Tokina) Reply with quote
Today I've compared my 24mm/F2.8 SLR lenses on my Ricoh GXR-M:

Minolta AF / Tokina RMC / Minolta MD (version MD III) / Pentax K SMC

All pictures shot WO at F2.8 in order to show the worst case performance and each picture is followed by a 100% crop from the very right side.

Minolta AF





Tokina RMC





Minolta MD





Pentax SMC





IMHO the Minolta MD is best, the Tokina is a positive surprise and the Pentax is worst.
However, if stopped down the differences disappear and latest at F8 you won't be able to differentiate those lenses; i.e. they are all very nice and sharp performers from edge to edge.


PostPosted: Mon Feb 13, 2017 6:05 pm    Post subject: Reply with quote
Like 1


PostPosted: Mon Feb 13, 2017 7:26 pm    Post subject: Reply with quote
I am very pleased to see this test as I have a Hoya HMC 2.8/24 in as new condition except that it's aperture blades are stuck open. I believe this lens was manufactured by Tokina and is the same lens as their RMC 24mm. I will put it to the top of my repair list.


PostPosted: Mon Feb 13, 2017 8:16 pm    Post subject: Reply with quote
Very nice performance from Tokina. Question remains, would it perform so good on a FF too? Smile


PostPosted: Mon Feb 13, 2017 8:35 pm    Post subject: Reply with quote
Excellent! Thanks


PostPosted: Mon Feb 13, 2017 8:51 pm    Post subject: Reply with quote
y wrote:
Very nice performance from Tokina. Question remains, would it perform so good on a FF too? Smile


On film it was always excellent (I bought it already in the early 1980's). I am not able to test it on my FF digital camera due to mount incompatibility.


PostPosted: Mon Feb 13, 2017 8:56 pm    Post subject: Reply with quote
tb_a wrote:
I am not able to test it on my FF digital camera due to mount incompatibility.


I will when I repair my Hoya branded Tokina as it has a M42 mount.


PostPosted: Mon Feb 13, 2017 9:02 pm    Post subject: Reply with quote
DigiChromeEd wrote:
tb_a wrote:
I am not able to test it on my FF digital camera due to mount incompatibility.


I will when I repair my Hoya branded Tokina as it has a M42 mount.


OK, I will instead use my Minolta AF lens which isn't bad either. Wink


PostPosted: Mon Feb 13, 2017 9:55 pm    Post subject: Reply with quote
Thanks for this.

IMHO all wide angle comparison tests are flawed. Smile

Please, how was in-focus determined?

My own wide angle tests show field curvature can greatly magnify the slightest focus error. There can be quite a large range of "exact" focus at the center of the lens; edge focus will be worst at the ends of that focus range.

I have since wondered if a more accurate edge-focus comparison can be obtained by using the edge to focus, rather than the center?


PostPosted: Tue Feb 14, 2017 12:02 am    Post subject: Reply with quote
visualopsins wrote:
Please, how was in-focus determined?


The focus was set to the buildings in the center of the images.

visualopsins wrote:
My own wide angle tests show field curvature can greatly magnify the slightest focus error. There can be quite a large range of "exact" focus at the center of the lens; edge focus will be worst at the ends of that focus range.
I have since wondered if a more accurate edge-focus comparison can be obtained by using the edge to focus, rather than the center


If you set the focus by using the edge then the center may be out of focus. That's at least my experience. However, if a lens fails due to strong field curvature then I don't need it anyway.


PostPosted: Tue Feb 14, 2017 8:59 am    Post subject: Reply with quote
Very impressive performance by the Tokina and Minolta MD. I have the MD-II version of the Minolta (different optics) and I think it's not as good. Perhaps sharpness itself is not worse but there is much more field curvature, I think.


PostPosted: Tue Feb 14, 2017 9:20 am    Post subject: Reply with quote
miran wrote:
Very impressive performance by the Tokina and Minolta MD. I have the MD-II version of the Minolta (different optics) and I think it's not as good. Perhaps sharpness itself is not worse but there is much more field curvature, I think.


Well, the Tokina was my only 24mm lens for decades as I couldn't afford to buy the Minolta one those times.
When I finally got my Minolta MD lens a couple of years ago I've tried to sell the Tokina one and I didn't get even 30 Euros then. So I kept it till date. Nowadays the average selling price is already almost 100 Euro for that lens (Ebay). So actually I'm lucky that I didn't sell it those days. Wink

Indeed, the MD III is an outstanding lens. I'm really happy to have it.


PostPosted: Fri Feb 17, 2017 1:53 am    Post subject: Reply with quote
tb_a wrote:
visualopsins wrote:
Please, how was in-focus determined?


The focus was set to the buildings in the center of the images.


I was asking how that was accomplished, ie, optical viewfinder, digital viewfinder, digital viewfinder magnified, cued by focus indicators or using eyesight, etc.. And, if lens focus ring was turned to bring from infinity to closer, or vice versa, was that same method used for each lens.

tb_a wrote:
visualopsins wrote:
My own wide angle tests show field curvature can greatly magnify the slightest focus error. There can be quite a large range of "exact" focus at the center of the lens; edge focus will be worst at the ends of that focus range.
I have since wondered if a more accurate edge-focus comparison can be obtained by using the edge to focus, rather than the center


If you set the focus by using the edge then the center may be out of focus. That's at least my experience. However, if a lens fails due to strong field curvature then I don't need it anyway.


Yes, my experience also. Of course usual to stop down to increase dof to bring both into best focus at once.

Lens curvature not due to too shallow dof?


PostPosted: Fri Feb 17, 2017 3:57 am    Post subject: Reply with quote
visualopsins wrote:
I was asking how that was accomplished, ie, optical viewfinder, digital viewfinder, digital viewfinder magnified, cued by focus indicators or using eyesight, etc.. And, if lens focus ring was turned to bring from infinity to closer, or vice versa, was that same method used for each lens.


OK, I used the optional digital viewfinder of my Ricoh GXR-M. The camera has a fantastic focus aid (magnification and "sparkling" edges) as the M-module was developed for the exclusive use of manual focus lenses. It was done manually for each and every shot at the same point within the picture (building in the center). This must be done like this because some of the lenses/adapter combinations tend to focus beyond infinity. Only when using genuine Leica M-mount (or M39/LTM) lenses I can trust the scale on the lens; i.e. I would be able to set to infinity without further control. However, in this test only adapted lenses have been used. And yes, the same method was used for every lens.

visualopsins wrote:
Yes, my experience also. Of course usual to stop down to increase dof to bring both into best focus at once.
Lens curvature not due to too shallow dof?


Well, therefore I mentioned that this test shows the worst case scenario with open aperture and relatively shallow DOF. In other words: If stopped down the corners would improve. I would not recommend to use open aperture for infinity landscape pictures anyway. I never do this myself for normal landscape shooting in order to get maximum DOF and quality.

Therefore my conclusion was that all of the used lenses of this test case are capable to deliver good and sharp picture in real practice:
Quote:
... if stopped down the differences disappear and latest at F8 you won't be able to differentiate those lenses...

I simply skipped the step to show all of those stopped down pictures. You have to trust me a little bit in that respect. Wink
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