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Sigma 30mm 2.8 or Minolta MC/MD+Focal reducer???
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PostPosted: Fri Nov 18, 2016 2:42 pm    Post subject: Sigma 30mm 2.8 or Minolta MC/MD+Focal reducer??? Reply with quote

Dear Experts,
I am using a Sony A6000 body with both the Sony SEL50/1.8 and a Minolta 50/1.7. I am happy with the results of both lenses, but I am looking for a bit of wider angle to be used for indoor family shots (low light).
Which one you suggest me to go with:
- Sigma E mount AF 30mm 2.8 DN ($150 USD, used).
- A Focal reducer for my Minolta 50 mm (1.7 & 1.4) ($100-150 USD).
The ease of Sigma AF is quite interesting, specially for taking photos of kids playing and for some people who are not patient enough. However, with the focal reducer, I was wondering of having a faster lens and shallower DOF with creamy bokeh for portraits, and more fun to play with.

Which one do you find better for indoor shots?
Any general advice will be much appreciated.


PostPosted: Fri Nov 18, 2016 3:13 pm    Post subject: Reply with quote

go for the sigma, is a great small lens! I regret to have sold mine when i switched to a7


PostPosted: Fri Nov 18, 2016 3:24 pm    Post subject: Reply with quote

Rick1779 wrote:
go for the sigma, is a great small lens! I regret to have sold mine when i switched to a7


So, you believe that it's a good performer for my application?? (indoor group shots).


PostPosted: Fri Nov 18, 2016 3:40 pm    Post subject: Reply with quote

Rick1779 wrote:
go for the sigma, is a great small lens! I regret to have sold mine when i switched to a7


I agree, a great little lens for little money. So too are the 19mm and 60mm from the same series.


PostPosted: Fri Nov 18, 2016 7:05 pm    Post subject: Reply with quote

If you're after sharpness and contrast and generally top image quality, go for the Sigma. However autofocus performance will be so-so and for manual focus it can't even begin to compare to any old manual focus lens. And the difference in DOF and light gathering ability will be huge. A 50/1.4 with a 0.7 focal reducer will be close to 35/1.0, so around 3 stops faster than the 30/2.8. That's the difference between ISO400 and ISO3200 for example. But then again using the 50/1.4 wide open will only work for individual portraits and even then DOF will be tiny. For group shots you'll be better served with the 30/2.8 and a flash. Bottom line: Sigma 30/2.8 for general purpose shooting and top image quality, 50/1.4 + focal reducer for special purposes (min DOF individual portraits) and "artistic" image quality.


PostPosted: Wed May 15, 2019 4:27 pm    Post subject: Reply with quote

miran wrote:
A 50/1.4 with a 0.7 focal reducer will be close to 35/1.0, so around 3 stops faster than the 30/2.8.


I know it's old thread but I cannot help myself after reading such nonsense Miran Very Happy.

If you use 50/1.4 on Aps-c with obvious x 1.5 crop factor. So this lens will be equivalent of 75/2.1 on FF (50 x 1.5 and f stop as well so 1. 4 x 1.5)

Then if you use 0.7 focal reducer it's 75 x 0.7 and 2.1 x 0.7 making the lens 52.5/1.47 Smile

There's no magic in it, simple math. And focal reducers don't 'give' extra light or DOF in comparison with using the same lens on FF Wink. I don't know why, but people tend to multiply only focal length and forgot to multiply f-stop as well. If you then want to take focal reducer into your equation you always need to multiply your equivalent of Aps-c crop factor first.

Very simple test is to see it yourself - take A6000 or other APS-C with focal reducer take a photo and then use the same lens and settings (shutter, ISO, aperture) without focal reducer on FF camera.
It'll be the same exposure (+/- variation of particular ISO sensitivity on both cameras as they're never exactly the same)

Granted this 50/1.4 with focal reducer will still be a lot 'faster' than this Sigma 30/2.8 which is lens optimised for APS-C and is equivalent of 45/4.2 on FF (remember - multiplying both focal length and f-stop)


Edit:
I just have read my post and noticed it might have sounded a bit rough. I'm terribly sorry Miran as it wasn't my intent to be rude to you, as I'm sure you know all that, but simply messed something up by mistake or quick writing Smile.
I just wanted that future readers, who are new to the topic won't be mislead.
Cheers


PostPosted: Wed May 15, 2019 9:00 pm    Post subject: Reply with quote

PhantomLord wrote:
I know it's old thread but I cannot help myself after reading such nonsense Miran Very Happy.

If you use 50/1.4 on Aps-c with obvious x 1.5 crop factor. So this lens will be equivalent of 75/2.1 on FF (50 x 1.5 and f stop as well so 1. 4 x 1.5)

Then if you use 0.7 focal reducer it's 75 x 0.7 and 2.1 x 0.7 making the lens 52.5/1.47 Smile

You are wrong on every calculation regarding how focal reducer works.
I think you fooled yourself when you began using "equivalents", which is a sure way to confuse anyone, starting with yourself.

50/1.4 stays 50/1.4 no matter which sensor is behind it.
It even stays 50/1.4 while sitting in box, not attached to a camera.
It continues to stay that way sitting on a focal reducer too, but the whole system now acts as a ~36/1.0.

PhantomLord wrote:
There's no magic in it, simple math. And focal reducers don't 'give' extra light or DOF in comparison with using the same lens on FF Wink.

They very much do give an increase in light intensity.
If you reduce your image circle, what would you think will happen with the light intensity per surface area?
Finally, your last point is the single correct one so far: the DOF will be close to the original one as found on the FF.



PhantomLord wrote:
Very simple test is to see it yourself - take A6000 or other APS-C with focal reducer take a photo and then use the same lens and settings (shutter, ISO, aperture) without focal reducer on FF camera.
It'll be the same exposure (+/- variation of particular ISO sensitivity on both cameras as they're never exactly the same)

I have two focal reducers, and an FF body.
It's clear to me you have not bothered with performing your own experiment.
Why should anyone then?

PhantomLord wrote:

Granted this 50/1.4 with focal reducer will still be a lot 'faster' than this Sigma 30/2.8 which is lens optimised for APS-C and is equivalent of 45/4.2 on FF (remember - multiplying both focal length and f-stop)

Real-world outstanding low-light capabilities with fast lenses and focal reducers are very much true.
You will gain three full stops on Sigma 30/2.8 and it will make certain impossible shots to be well within camera performance profile.

Here are couple shots made with focal reducer which are impossible, or at the very lest, are extremely unlikely with any native lens without stabilization:




PhantomLord wrote:
I just wanted that future readers, who are new to the topic won't be mislead. Cheers

I wasn't about to grill you, but you sort of triggered me here.


PostPosted: Wed May 15, 2019 10:48 pm    Post subject: Reply with quote

aidaho wrote:

I think you fooled yourself when you began using "equivalents", which is a sure way to confuse anyone, starting with yourself.


Could you please elaborate on that. Maybe I'm wrong, I won't be saying that I'm infallible Smile. However, calculating focal length and f-stop as an equivalent to the 35 mm film frame is nothing that I've invented. It's being used for some time now as a common denominator.

aidaho wrote:

50/1.4 stays 50/1.4 no matter which sensor is behind it.
It even stays 50/1.4 while sitting in box, not attached to a camera.


There's nothing to add here Smile, I totally agree. However it'll be acting differently if you put in front of different sensors and of course sitting in box it may not be all that useful.

aidaho wrote:
but the whole system now acts as a ~36/1.0.


Do you mean that in situation when we put 50/1.4 on APS-C+focal reducer we will achieve roughly the same DOF and FOV as if you put ~36/1.0 lens on this sensor without focal reducer?
If so, I totally agree, but there's no contradiction to what I wrote, or maybe I'm not seeing it Smile.

Well... putting this 36/1.0 lens in equivalent of FF sensor 36*1,5=54 1,0x1,5=1,5 is almost 50/1.4. I don't understand why you don't like equivalents Very Happy.


aidaho wrote:

PhantomLord wrote:
There's no magic in it, simple math. And focal reducers don't 'give' extra light or DOF in comparison with using the same lens on FF Wink.

They very much do give an extra light. If you reduce your image circle, what would you think will happen with the light intensity per surface area?
Finally, your last point it the single correct one so far: the DOF will be close to the original one as found on the FF.

PhantomLord wrote:
Very simple test is to see it yourself - take A6000 or other APS-C with focal reducer take a photo and then use the same lens and settings (shutter, ISO, aperture) without focal reducer on FF camera.
It'll be the same exposure (+/- variation of particular ISO sensitivity on both cameras as they're never exactly the same)

I have two focal reducers, and an FF body.
It's clear to me you have not bothered with performing your own experiment.
Why should anyone then?


I try to answer both of them if you don't mind.
I did try what I've wrote, just before writing it. Exactly because I don't like saying something without prior confirmation. I may be wrong, but still I did exactly what I've wrote.
I've put 50/1.4 on A7 and shoot the scene at ISO 200, 1.4, 1/50s. Then I've put focal reducer on X-E1, the same 50/1.4 and shoot the same scene from the same distance with the ISO 200, 1.4, 1/50s.
Result was quite visible - difference between exposure was negligible.

Now, as I'm writing this reply I've try a bit different approach: I've took only Fuji X-E1, Olympus Zuiko 50/1.4 and tested it with and without focal reducer, at the same time trying to achieve the same field of view in both shots and then A7 with same lens.
1) 50/1.4 on X-E1 without focal reducer
2) 50/1.4 on X-E1 with focal reducer (Lens Turbo II in this case).
3) 50/1.4 on Sony A7
I know the scenes are not perfectly aligned, but it's late and I wanted it to be close enough Wink

ISO 800 and f/1.4 in both situations and I was aiming at the same exposure, which gave me 1/50 (without focal reducer) and 1/70 (with focal reducer) and 1/80 on A7.

Sorry for my messy kitchen and AWB on A7 sucks in this LED light Very Happy, X-E1 managed better here. All photos are JPG's straight out of cameras, EXIF's are there if you would like to check.
#1


#2


#3


So am I missing something? DOF and FOV were almost the same and honestly exposure values are roughly the same - in the margin of 0.3EV.

aidaho wrote:

You will gain three full stops on Sigma 30/2.8 and it will make certain impossible shots to be well within camera performance profile.


Well... you've confused me here. It's obvious that combo APS-C+Focal reducer+50/1.4 will be about 3 stops faster than this Sigma 30/2.8 (plain on APS-C, without focal reducer of course). I wrote exactly that here:
PhantomLord wrote:
Granted this 50/1.4 with focal reducer will still be a lot 'faster' than this Sigma 30/2.8 which is lens optimised for APS-C and is equivalent of 45/4.2 on FF
difference between f/1.4 and f/4 is 3 stops, so it was clear in my previous post.
But putting this 50/1.4 on APS-C+Focal reducer won't give you 3 stops more light than the same 50/1.4 on FF sensor from what I see on my cameras.

aidaho wrote:

Here are couple shots made with focal reducer which are impossible, or at the very lest, are extremely unlikely with any native lens without stabilization:

I like the second - kid peeping Smile, nicely captured, girl is certainly trying hard Very Happy.
But honestly I'm not seeing those photos as impossible to capture on FF camera with the same lens you've used.

aidaho wrote:
I wasn't about to grill you, but you sort of triggered me here.

I suppose we all have our irks Very Happy.
No hard feelings obviously, as I've stated - I might be wrong, or I might be missing something, so please keep this discussion up and try to explain even further please.

All in all I see that we agree on some things, but maybe we're saying it differently.
The main difference is about those "3 more stops of light" that you're getting and I cannot find on my focal reducer Wink.


PostPosted: Thu May 16, 2019 8:31 am    Post subject: Reply with quote

PhantomLord wrote:
aidaho wrote:

I think you fooled yourself when you began using "equivalents", which is a sure way to confuse anyone, starting with yourself.


Could you please elaborate on that. Maybe I'm wrong, I won't be saying that I'm infallible Smile. However, calculating focal length and f-stop as an equivalent to the 35 mm film frame is nothing that I've invented. It's being used for some time now as a common denominator.


It is indeed a convenient way to get a point on FOV and DOF across.
It is just that however: a virtual substitute to roughly compare stuff.
Using them for anything else brings us to where we are now.


PhantomLord wrote:
Well... putting this 36/1.0 lens in equivalent of FF sensor 36*1,5=54 1,0x1,5=1,5 is almost 50/1.4. I don't understand why you don't like equivalents Very Happy.

Maybe if you start marking your units accordingly, as imff (imaginary FF milimiters) and imapsc, imfstop you'll be able to solve this.
In the meantime, I'm still for using real units in calculations as to avoid confusion.


PhantomLord wrote:
I did try what I've wrote, just before writing it.

I guess now I have to do the same:



One full stop gained by APS-C body on shutter speed.
In truth that's slightly lower that one T-stop, but my point stands: with the same scene and metering you will get a one stop advantage in iso or shutter speed over FF without fail.

PhantomLord wrote:

But putting this 50/1.4 on APS-C+Focal reducer won't give you 3 stops more light than the same 50/1.4 on FF sensor from what I see on my cameras.

We are in agreement here. You'll get one stop advantage compared to the same lens on FF. Three stops, if we are to put 50/1.4 on reducer and meter it against Sigma 30/2.8 on aps-c body.

PhantomLord wrote:

But honestly I'm not seeing those photos as impossible to capture on FF camera with the same lens you've used.

I continued talking about APS-C and it's native lenses. Perhaps I should've made this more clear.

PhantomLord wrote:

All in all I see that we agree on some things, but maybe we're saying it differently.
The main difference is about those "3 more stops of light" that you're getting and I cannot find on my focal reducer Wink.

I've scrolled up, and I believe no one made a statement you are trying to refute.
The comparison was between focal-reduced vintage 50/1.4 and Sigma 30/2.8.


PostPosted: Thu May 16, 2019 10:53 am    Post subject: Reply with quote

aidaho wrote:

It is indeed a convenient way to get a point on FOV and DOF across.
It is just that however: a virtual substitute to roughly compare stuff.
Using them for anything else brings us to where we are now.


Well, using equivalents to compare FOV and DOF is mathematically exact Wink, but I agree I'm not thinking about it when shooting. I just take lens, camera and other equipment which suits my needs.

aidaho wrote:

PhantomLord wrote:
Well... putting this 36/1.0 lens in equivalent of FF sensor 36*1,5=54 1,0x1,5=1,5 is almost 50/1.4. I don't understand why you don't like equivalents Very Happy.

Maybe if you start marking your units accordingly, as imff (imaginary FF milimiters) and imapsc, imfstop you'll be able to solve this.
In the meantime, I'm still for using real units in calculations as to avoid confusion.


There's nothing imaginary here Very Happy, I don't know why are you so much against it. It's really simple math in terms of DOF and FOV.
But of course, I'm not pushing you to use it or not. However as far as manufacturer's are concern I see they use equivalent to FF values on their products, even if those products cannot be used on FF and are designed for APS-C, m4/3 or anything other. This Sigma 30 mm 2.8 in threads tittle - it's a lens designed for APS-C, but it's focal range and f-stop is described as FF equivalent.
From Sigma site - description of said Sigma 30/2.8: "The high-performance standard lens has an angle of view equivalent to 60 mm on the Micro Four Thirds system and 45 mm on the E-mount system (35mm equivalent focal length)"
As I said, I haven't invented it Wink.


aidaho wrote:

I guess now I have to do the same:

One full stop gained by APS-C body on shutter speed.
In truth that's slightly lower that one T-stop, but my point stands: with the same scene and metering you will get a one stop advantage in iso or shutter speed over FF without fail.


And now we're getting somewhere. As you have showed (just as I did in previous post) - there is some EV difference when comparing APS-C + Focal Reducer with FF sensors. Granted, I stand corrected that there's a bit more light - in my comparison it was more like 0,3EV, in yours it was 1,0EV. All right. But it needs to be said clear, that we're not talking about f-stops, but about amount of light, so t-stops.

I should have wrote that more clearly in my previous post - I've understood Miran's and your's posts in a wrong way. I thought that you think you'll get 3 stops of light just by using focal reducer Smile. Mainly because of what you wrote:
aidaho wrote:
Real-world outstanding low-light capabilities with fast lenses and focal reducers are very much true.

And in my mind 0,3-1,0EV is nothing outstanding.
Certainly not much of a difference and honestly nowadays with cameras' ISO performance is almost negligible. One should not forget that you also loose sharpness and details and it's a loss that you can't "fix" by bumping up ISO a bit higher.
Anyway, even if you take 50/1.4 of four different manufacturers you'll measure different t-stops for each lens. One will need 1/60 and the other 1/125 to get proper exposure in the same conditions and camera/lens settings.
Good low-light capabilities are a bit more complex equation than just slapping focal reducer on APS-C camera and I'm pretty sure you are aware of it so there's no need to digress even more.

Don't get me wrong I'm not saying that Focal reducers are terrible idea. On the contrary, I've used one for several years and I was very pleased with the results (well maybe except some sharpness loss, usually noticeable at wide open). I only take into consideration this "you get more light" argument as not that striking (Although it's great marketing slogan Wink ).
That said, I agree that I was wrong - yours and my examples clearly showed faster shutter speed on camera with focal reducer. And I'm glad that you've corrected me.

I'm not sure, however, if both of us agree about multiplying focal length and f-stop for DOF and FOV comparison. You have your view, I have mine and you haven't presented any argument on the matter so we could either leave it as it is or try convince each other (which probably won't be easy Very Happy).

All in all, I've resurrected 2,5 year old thread and I wonder, what was the choice of author in the end Smile - Sigma or Focal reducer?


PostPosted: Thu May 16, 2019 1:35 pm    Post subject: Reply with quote

PhantomLord wrote:

There's nothing imaginary here Very Happy, I don't know why are you so much against it. It's really simple math in terms of DOF and FOV.

I'm trying to explain, but have trouble getting across.


PhantomLord wrote:

But of course, I'm not pushing you to use it or not. However as far as manufacturer's are concern I see they use equivalent to FF values on their products, even if those products cannot be used on FF and are designed for APS-C, m4/3 or anything other.

Could you list at least one? I have not come across a lens with parameters inscribed in some equivalence units.


PhantomLord wrote:

This Sigma 30 mm 2.8 in threads tittle - it's a lens designed for APS-C, but it's focal range and f-stop is described as FF equivalent.

This is simply not true. Those are not "FF eqivalent", just plain old millimeters and maximum relative opening.
https://en.wikipedia.org/wiki/Focal_length
No such thing, as "full-frame millimetres".


PhantomLord wrote:

From Sigma site - description of said Sigma 30/2.8: "The high-performance standard lens has an angle of view equivalent to 60 mm on the Micro Four Thirds system and 45 mm on the E-mount system (35mm equivalent focal length)"
As I said, I haven't invented it Wink.

Yes, within rough comparison application, that's a widely acceptable convenience method, I've covered this above:
aidaho wrote:

It is indeed a convenient way to get a point on FOV and DOF across.
It is just that however: a virtual substitute to roughly compare stuff.

Thank heavens, no one yet thought of inscribing "equivalent millimeters" on the lenses themselves.
Or make calculations based on them.


PhantomLord wrote:
All right. But it needs to be said clear, that we're not talking about f-stops, but about amount of light, so t-stops.

I should have wrote that more clearly in my previous post - I've understood Miran's and your's posts in a wrong way.

This is exactly the point I'm trying to get across: your misunderstanding stems from your desire to use equivalence.
At no point in this discussion FF had any relevancy.
The ambiguity in what to do with the second value comes from introducing equivalence to FF.
Have you not brought FF into the equation, this misunderstanding would simply not happen.


PhantomLord wrote:
I thought that you think you'll get 3 stops of light just by using focal reducer Smile. Mainly because of what you wrote:
aidaho wrote:
Real-world outstanding low-light capabilities with fast lenses and focal reducers are very much true.

And in my mind 0,3-1,0EV is nothing outstanding.

I belive I left no room for such interpretation.
I can't be entirely sure, as English is not my native tongue, but I think I expressed myself very unambiguously:
aidaho wrote:
Real-world outstanding low-light capabilities with fast lenses and focal reducers are very much true.
You will gain three full stops on Sigma 30/2.8 and it will make certain impossible shots to be well within camera performance profile.

I can't see through which crack in my statement FF body, and comparison to it, entered the equation again.


PhantomLord wrote:

Certainly not much of a difference and honestly nowadays with cameras' ISO performance is almost negligible. One should not forget that you also loose sharpness and details and it's a loss that you can't "fix" by bumping up ISO a bit higher.

I disagree. I do want to trade my sharpness for T-stops at night.
Having "too soft 1.0 for a daytime" is a godsend at night.
Nothing affects sharpness more than a smeared picture, and noise reduction for high ISO chews up IQ better than some lenses do.


PhantomLord wrote:

I'm not sure, however, if both of us agree about multiplying focal length and f-stop for DOF and FOV comparison. You have your view, I have mine and you haven't presented any argument on the matter so we could either leave it as it is or try convince each other (which probably won't be easy Very Happy).

I believe I presented enough evidence to show how equivalence resulted in a systematic error of judgement.


I do call them imaginary, because they are just that.
Unfortunately this is far from the first case on the web, where I see them misused. To list a few:
Ever saw ebay sellers list a FF 50/2 lens with m4/3 adapter as "100mm F2"?
Ever heard of people trying to figure out why they should treat FF 50/2 as 75/2.8 on apsc, but not vice versa?
And so it goes.


I believe I have fully presented my case against using equivalence for anything but rough comparisons, while clearly stating so, like that Sigma quote.
Let other people be the judge though.


PostPosted: Thu May 16, 2019 1:44 pm    Post subject: Reply with quote

Very well Aidaho, you're really emotional about the subject, I don't know why, but that's OK. I won't be upsetting you any longer with my imaginations as you have kindly described them Wink.

I still, however can't see the problem with equivalences. But at the same time I leave some room for doubts and if at any time I learn my thinking to be absolute rubbish be sure that I'll come to you admitting that.

In the meantime I wish you best of luck and nice captures, as that's the most important, despite our differences.
Take care Aidaho.

Edit: About those 50/2 listed with m4/3 adapter as 100/2...we're totally in agreement here.
I would list it as 100/4 Very Happy (just kidding of course, seriously take care).