Just ordered a cheap Chinese Mirror lens - Pros and cons...

[Mike_9000]

It's 500mm f8, and I ordered direct from Ali Express - so nobody on ebay or Amazon (or anywhere else) gets to apply a markup

I understand:

• They are incredibly short, compared to the alternative design of 'lens elements at either end of a very long tube'
• Manual focus - which is going to be a challenge on my Panasonic mirrorless cameras (a G90 and a GX9)
• Contrast is inherently low, compared to conventional lenses (although you can turn that up a bit in post)
• Paper-thin depth of field, with 'donut rings' in out of focus areas (something people tend to either love or hate)
• Fixed aperture (f8 in this case, although there are some that go to f6.5)
• Filters fit in a curious 'drawer' at the 'wrong' end of the lens
• The cheap ones come with a screw thread, and you need need to specify an adaptor with a suitable bayonet fitting
• There's no electronic communication with the lens - but since the aperture is fixed, it's not got much to tell you

Relating to Micro four-thirds: 500mm gives an equivalent field of view to 1,000mm on full-frame. Also, the T3 lens adaptor is a lot longer than those for full-frame, and I wonder why. Do MFT cameras only use the centre of the image circle, suggesting that purpose-built lenses could be even more compact?

In summary: they aren't as sharp as conventional lenses, and the contrast is poor. However, I have in-camera stabilisation and want it to cover protests - specifically ones where those at whom protest is aimed tend to retire to a distance. Getting a picture that isn't perfect is infinitely better that not getting one at all.

Comments and advice, please...

 

[woof woof]

If you're using MF lenses I can't think of a better place to put them than on a mirrorless camera.

Yes, of course, if you're using a larger format lens MFT only uses the central area so lenses specifically designed for MFT could well be smaller than those designed for a larger format.

The length of the adapter is decided by where the sensor is mounted as it serves two purposes, to make it possible to physically mount the lens on the camera and to place the lens at the correct distance from the sensor.

 

[Mike_9000]

The length of the adapter is decided by where the sensor is mounted as it serves two purposes, to make it possible to physically mount the lens on the camera and to place the lens at the correct distance from the sensor.

So the adaptor is acting like an extension tube 'distancing' the lens from the sensor so the centre of the field is 'projected' onto the sensor with the correct 2x crop factor.

I suppose purpose-made MFT mirror lenses would cost a lot more, not be much smaller, and I can use this one on other cameras just by acquiring another T3 edaptor.

If you're using MF lenses I can't think of a better place to put them than on a mirrorless camera.

Is that because of the ability to 'enlarge' a little window in manual-focus mode. I've not used that much to date, but I suppose I will now

 

[ancient_mariner]

Mirrorless cameras can sometimes help manual focus through focus peaking in the viewfinder.

FWIW I have a 600 sigma mirror lens, and even on full frame, detail is low and contrast very soft. If you expect a poor performance then you might have a pleasant surprise, but if you hope it will be good then disappointment is likely.

 

[BillN_33]

It would (will) be interesting to see some images once you start to use the lens

 

[Mike_9000]

Mirrorless cameras can sometimes help manual focus through focus peaking in the viewfinder.

Is focus peaking where parts of the image seen highlighted, until you focus on that point? The only times I've used that is to shoot through chain-link fenced on manual.

FWIW I have a 600 sigma mirror lens, and even on full frame, detail is low and contrast very soft. If you expect a poor performance then you might have a pleasant surprise, but if you hope it will be good then disappointment is likely.

I'll likely only use it for fun, or to get pictures which could not be obtained otherwise, where quality less of an issue. I'm expecting quite poor... so I hope...

 

[Mike_9000]

It would (will) be interesting to see some images once you start to use the lens

When I get it (shipping from China is now painfully slow) I'll go to the park.
I'll take a 25mm (50mm full frame equivalent) lens and a tripod and compare the fields of view

 

[the black fox]

Think you will be pleasantly surprised , and Chinese lenses these days are far better than of old . I actually prefer Panasonic bodies/menus Over Olympus for m/f

 

[woof woof]

So the adaptor is acting like an extension tube 'distancing' the lens from the sensor so the centre of the field is 'projected' onto the sensor with the correct 2x crop factor.

I suppose purpose-made MFT mirror lenses would cost a lot more, not be much smaller, and I can use this one on other cameras just by acquiring another T3 edaptor.



Is that because of the ability to 'enlarge' a little window in manual-focus mode. I've not used that much to date, but I suppose I will now

Looks like you have a good grasp of what's going on but rather than think of the adapter as an extension tube (because I think that's a different thing) think of it as a "spacer" which allows the lens to be the correct distance from the sensor and so enable it to focus.

I think the magnified view is wonderful for MF.

 

[Mike_9000]

Can't wait to see the images you get from it.

The best approach is probably to go to the park, which nicely frames a view of the City Centre. This includes a very tall student accomodation building. I can set up a tripod, and just switch lenses until I get to the 500mm (equivalent to 1,000mm on full-frame) taking a shot each time.

There was another mirror lens at 900mm. Now that's a special-purpose device, specially on a small sensor.

Tracking says it hasn't left China yet, so watch this space.