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10-04-2014, 01:39 PM   #1
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A case for mirror lenses (Samyang 500mm f6.3 samples)

Nowadays when people hear about mirror lenses either they don't know what's that or they think it's crap quality.
I learned about mirror lenses while searching for cheap telephoto lenses and yea' they can get quite cheap!

What I think it's nice about them is:
- price: cheap
- size: small and light
- no Chromatic aberration
- nice bokeh (some people take this as a con)

What I think it's more of a drawback:
- very hard to focus - even after getting used to my Samyang I still get many improperly focused photos so I compensate by taking more
- not many choices in terms of settings: the minimum ISO i can use is 400 and I don't want to go above 3200. The exposures generally vary then between 1/200(very rarely) through 1/500(most common) and rarely below to 1/1000. Keep in mind that aperture is FIXED.
- usually bad contrast / washed out colors

So, there are drawbacks! Sometimes it can get really frustrating and I tell myself that I need a proper lens. But then I remember that I don't have those 2000 euros for the Pentax DA* 300mm and the teleconverter. Or the money for the Sigma telephoto tanks (which I wouldn't want to carry anyway, except if I'd work as a photographer which isn't the case).

Here are some photos that I took with the lens. Although I'm pretty sure that Sigma or Pentax 1500$ telephoto would've achieved much better than this, I'm pretty happy with what I've got. Thinking about the money I paid for it (115 euros for the new lens + hood + adapter + shipping) I think it was worth it.

I recently ordered the 3M-5CA 500mm f8 and it should arrive in a few days. I expect much more from that one in terms of sharpness and colors/contrast. From what I've seen on the net it is the best 500mm mirror lens. This is why I felt I should write this - A sort of an epilogue for my Samyang 500mm. The 2nd picture with the blue tit was done just a few hours ago in what was probably its last shooting with me.
For more of these photos show with the Samyang, you can visit my gallery in the birds category.
#1


#2


#3


#4


Last edited by misomosi; 05-11-2015 at 01:48 PM. Reason: removed links
10-04-2014, 02:41 PM   #2
dms
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The 2nd one also shows what it is capable of--that particular rendering would not likely be as good on a non-mirror lens.
10-04-2014, 04:09 PM   #3
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Nice results! I agree the bokeh on the second one is pleasing and unique, but they all are good.
10-04-2014, 04:41 PM   #4
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I personally also like the bokeh in the 3rd one - looks like some post processing effect but no, it's just sun lit leaveless branches from some farther tree.
Here's one with a similar feel as the 2nd one.


Last edited by misomosi; 05-11-2015 at 01:48 PM.
10-04-2014, 05:10 PM   #5
Des
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Thanks for posting these photos and comments.

You make the case for this mirror lens well. But against that I would argue that for most people on a tight budget (say, less than $US200) a consumer telephoto such as the Pentax DA-L 55-300 (or Sigma or Tamron 70-300) would be a better choice:
- Lighter weight (Pentax 55-300 weighs about 440g against about 700g for the Samyang, or 620g + adapter for the Russian one)
- autofocus
- variable aperture (Pentax is f5.8 at 300mm)
- zoom range
- better bokeh (I know this is a matter of taste, but I would surely tire of the donuts from the mirror lens)

The manual focus on the Pentax 55-300 is not great, but it doesn't seem the Samyang is either!

The big question is whether the IQ of the mirror lens is so far superior as to overcome these disadvantages. The consumer tele zoom would certainly be more prone to CA (the Tamron 70-300 is notorious for it), but that could be improved a lot in PP. I note your comment in your review that the Samyang is not good for a subject more than 20m away. I suspect that a photo of a subject 20m away taken with the 55-300 at 300mm f6.3 (using a 16Mp camera) cropped to the equivalent field of view would be no worse, and in fact possibly better, than ones from the Samyang posted above.

If the Russian lens is the best of the mirror lenses the equation might be different - will be interesting to see your experience.
10-04-2014, 08:44 PM   #6
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I have the Sigma 600/8, which is touted as better than the rest of the crowd there. I bought it used from a Toronto Professor for just CAD 120 in Pentax mount - mint condition with hood, filters and the original caps. it certainly takes better photo than the ones with the Samyang shown here. I compensate for the color and contrast in LR 5.6 to equal the photo taken with a Sigma 150 - 500 mm lens.
But at 800 grams it is not a light lens. Solid metal, built like a tank. A good buy. The Russian lens is heavier and requires adapters. Wish I was in birding/wildlife /nature to use it more often.
Regards.
10-05-2014, 02:23 AM   #7
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Des, you point is good but there's something missing from the picture. Even at 500mm I need to crop. Out of the 4 pictures 1 & 4 are just slightly cropped because the birds are big enough - but for the small birds, apart from the fact that I try to get as close as 4-6m, I still need to crop: no2. is 9MP, no.3 is 10MP out of 16 original so roughly 0.6 the original size.

Out of curiosity, I made a small calculus and deduced the area ratio knowing that for 500mm the angle is 5deg. and 300mm is 8deg. The final formula is A300 / A500 = ( tan(2.5) / tan(4) ) ^ 2. The ratio is 0.625. Now with a 300mm lens a typical area for a small bird would be 0.625 * 0.6 = 0.375 the size of the sensor which gives 6MPX instead of the ~10MP I got with the 500mm.

I remembered i thought about this when I initially bought the lens and came to the conclusion that I need at least a 24Mp sensor to be able to use that (say) Tamron xx-300 lens,

But I agree, for a few dollars more one might get zoom and variable aperture.

I'm really curious about the 3M-5CA now - I'll probably do some comparative tests with the Samyang and post them someday.

10-05-2014, 05:04 AM   #8
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Des

I think you are forgetting that people who get mirrors are looking to go well beyond 300mm. Shooting wildlife is always about cropping. So there is another way. Get a Q. A Q turns a 200mm lens into a 1000 mm equivelent. So even cropping you have more pixels to work with.

I want to look again at my celesta on C90 because I think it will have less CA than most lenses and that is critical on the Q.
10-05-2014, 05:22 AM - 1 Like   #9
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QuoteOriginally posted by misomosi Quote
I recently ordered the 3M-5CA 500mm f8 and it should arrive in a few days.
I use a Sigma 170-500mm lens bought after trying out an MTO 500mm lens; I have tried a few mirror lenses and the MTO was the best of these. I was frustrated by the lack of iris control, autofocus and the doughnut effect. But certainly the MTO gave very nice results and was worthwhile as a cheapish way to see if a 500mm lens is for you before splashing out a significant amount of cash.
10-05-2014, 06:22 AM   #10
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QuoteOriginally posted by Lowell Goudge Quote
Des
I think you are forgetting that people who get mirrors are looking to go well beyond 300mm. Shooting wildlife is always about cropping. So there is another way. Get a Q. A Q turns a 200mm lens into a 1000 mm equivelent. So even cropping you have more pixels to work with.
Good point Lowell.

There seem to be several schools of thought about photographing wildlife in Pentax. In roughly descending order of cost:
1. A high quality long AF prime (400mm or more).
2. High quality 300mm prime (or premium zoom, like the Sigma 100-300 f4) and teleconverter (near $2,000 for the DA*300 + new Pentax 1.4x TC).
3. Long zoom, such as the Bigma (50-500) or maybe the forthcoming Pentax long tele zoom.
4. Small sensor Q with a sharp medium telephoto lens (e.g. DFA 100).
5. MF prime with TC or cropping. This would include mirror lenses.
6. Consumer 300mm zoom (e.g. Pentax 55-300) with TC or cropping.
I considered all of these and went with options 3 and 6. Not sure that I would make the same choice again.

---------- Post added 10-06-14 at 12:31 AM ----------

QuoteOriginally posted by misomosi Quote
Des, you point is good but there's something missing from the picture. Even at 500mm I need to crop. Out of the 4 pictures 1 & 4 are just slightly cropped because the birds are big enough - but for the small birds, apart from the fact that I try to get as close as 4-6m, I still need to crop:
I know what you mean. I have a zoom that runs to 500mm and I still need to crop unless it is a large bird or very close. 300mm requires a lot more cropping. More reach is good, but it usually comes with compromises (e.g. weight and price of the lens, need for tripod, etc).

In terms of the scope for cropping, the 16mp K-30 was a big improvement for me over my old 6mp K100D Super; I guess the 24mp K-3 would be another leap again.
10-12-2014, 07:15 AM - 1 Like   #11
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As promised, the comparision between the Samyang and 3M-5CA.
10-12-2014, 09:12 AM   #12
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Nice report and pretty comprehensive.
10-12-2014, 02:11 PM   #13
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Well done Darius. Excellent report.

As a footnote, Minolta used to make an autofocus mirror lens (500mm f8), so it can be done.
Minolta AF 500mm Reflex lens - Wikipedia, the free encyclopedia

Anyone considering a mirror lens will also find this article useful:
http://advancedphototech.wordpress.com/lenses/mirror-mirror-a-guide-to-choos...mirror-lenses/

Last edited by Des; 10-12-2014 at 02:21 PM.
10-13-2014, 12:13 AM   #14
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Thank you.

Now putting things into perspective - an AutoFocus, variable aperture, optically improved mirror lens would be an awesome idea for a startup company, if the big guys don't want to do this.
10-13-2014, 10:19 AM   #15
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If you want a variable aperture for the mirror lens I recall simply blocking part of the front objective will do it. With high ISO now available the gain in DOF should be usable.

Anyway I did a quick Google search and the first reference I found talks about a circular cutout. Mirror lenses

But as I recalled that is not needed--and continued and found the second (more desirable?) approach. Improving A Samyang 800mm With A Tuning Key And Some Cardboard - DIY Photography

There are probably other better sources/discussion as I only did a quick search for mirror lens and cardboard aperture.

Last edited by dms; 10-13-2014 at 10:26 AM.
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