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APS-C lens on SL factor question


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#1 rafael_macia

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Posted 20 June 2017 - 00:12

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I am using a Sigma 8-16 APS-C lens on the SL to shoot 4K video. 

Is there a factor involved?

Does the Sigma 8-16 become a 12-24 when using it with the SL switched to APS-C.

 

I know when I use a full frame lens, and I am shooting 4K my frame is within the Super 35 area. I have a crop factor of 1.5, (or 1.6 ... I am not sure.)

 

The Sigma, by the way is a nice lens .... but I think I want the Canon 11-24 f4. I want a constant f stop. I don't like variable aperture.

 

thanks


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#2 LD_50

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Posted 20 June 2017 - 00:38

APS-C is 1.52 crop on the SL.

4K is shot at 4196x2180 max. This is Super 35, or slightly smaller than APS-C with about a 1.55 crop.

Edited by LD_50, 20 June 2017 - 00:47.


#3 rafael_macia

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Posted 20 June 2017 - 00:57

APS-C is 1.52 crop on the SL.

4K is shot at 4196x2180 max. This is Super 35, or slightly smaller than APS-C with about a 1.55 crop.

 

Thanks for the exacting specs!

I will rephrase my question so it is hopefully understood.

 

 

I am asking;   ......       if using an APS-C lens (like the Sigma 8-16, I mentioned) to shoot 4K (3840x2160).On an SL

Is there a factor....(or crop, as you say)?

 

The reason I ask is the Sigma, being an ASP-C lens, sort of has , by its coverage, an automatic factor. ..... When shooting on a full frame camera.

I am sorry, but it is difficult to explain further what I am asking, so you can understand.


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#4 LD_50

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Posted 20 June 2017 - 03:23

Sigma 8-16 (even if an APS-C lens) would still need to be multiplied by the crop factor. I don't know of any APS-C lens makers that label their lenses with the crop built into the focal length labels.
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#5 ramarren

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Posted 20 June 2017 - 03:49

I am asking;   ......       if using an APS-C lens (like the Sigma 8-16, I mentioned) to shoot 4K (3840x2160).On an SL

Is there a factor....(or crop, as you say)?

 

The reason I ask is the Sigma, being an ASP-C lens, sort of has , by its coverage, an automatic factor. ..... When shooting on a full frame camera.

I am sorry, but it is difficult to explain further what I am asking, so you can understand.

 

I think I understand your question (confusion... :) ). 

 

All interchangeable lenses are marked with their actual focal lengths, not some 'equivalent focal length.' For example, an 8-16mm zoom lens has the same focal length on whatever format you put behind it. The actual field of view depends on both the focal length and the format you're shooting. So an 8-16 zoom will have the same field of view on a Leica SL set to APS-C format as any other 1.5x crop APS-C format camera, and a very slightly tighter field of view results when set to 4K movie capture.

 

The APS-C format on the Leica SL (16x24 mm format, 1.52x crop) produces a little bit wider field of view than the typical Canon APS-C format (14.9 x 22.3 mm format, 1.6x crop). 

 

Set to its native FF format (24 x 36mm), the Leica SL will image a much wider field of view with that same lens, but corner and edge quality will suffer on the FF format most likely, never mind that there will likely be a good bit of light falloff at corners and edges. 


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#6 Irakly Shanidze

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Posted 20 June 2017 - 08:16

Your question was thoroughly answered. The only think that i will add is that you cannot force SL to shoot full frame with APS-C lenses. Moreover, 4K option is only possible on a cropped sensor. Forget about millimeters, just look in the viewfinder.



#7 Irakly Shanidze

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Posted 20 June 2017 - 08:17

also... you might want to consider using Leica T lenses for 4K video instead of Sigma. Just so you can actually get what Leica SL is really capable of :)



#8 rafael_macia

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Posted 20 June 2017 - 14:00

Thanks for the replies !

 

regarding;

"you might want to consider using Leica T lenses"

 

I look for a fixed aperture, in a zoom. Which leaves out T lenses.

The R zooms fit the bill, the 35-70 f4 and the 80-200 f4, (the latter I have, and it is great!)

I would like to find a nice 35-70 f4 Vario Elmar

but mostly I am looking for a fixed aperture really wide zoom.

Hence the flirtation with the Sigma.

 

anyway

thanks again !


Edited by rafael_macia, 20 June 2017 - 14:03.

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#9 ramarren

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Posted 20 June 2017 - 15:53

Thanks for the replies !

 

regarding;

"you might want to consider using Leica T lenses"

 

I look for a fixed aperture, in a zoom. Which leaves out T lenses.

The R zooms fit the bill, the 35-70 f4 and the 80-200 f4, (the latter I have, and it is great!)

I would like to find a nice 35-70 f4 Vario Elmar

but mostly I am looking for a fixed aperture really wide zoom.

Hence the flirtation with the Sigma.

 

anyway

thanks again !

 

 

The variable aperture limitation should only impact you if you are shooting at wide-open aperture setting. I can't imagine shooting wide open for video in any scene where I also need to do coordinated focal length changes with the motion ... that may be my own limitation. :D

 

The SL's 'floating ISO' setting accommodates nicely the situation of shooting wide open stills with manual exposure on dedicated lenses where you are zooming in and out a lot by raising ISO by up to one stop to accommodate the longer focal length's maximum aperture. That one stop change in ISO is virtually indistinguishable to the eye. 

 

Please don't consider this as some kind of defense of the dedicated lenses. :)


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#10 Irakly Shanidze

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Posted 20 June 2017 - 22:35

Thanks for the replies !

 

regarding;

"you might want to consider using Leica T lenses"

 

I look for a fixed aperture, in a zoom. Which leaves out T lenses.

The R zooms fit the bill, the 35-70 f4 and the 80-200 f4, (the latter I have, and it is great!)

I would like to find a nice 35-70 f4 Vario Elmar

but mostly I am looking for a fixed aperture really wide zoom.

Hence the flirtation with the Sigma.

 

anyway

thanks again !

 

It really makes more sense to look for lenses with good image quality. SL has a wonderful feature called floating ISO, which works wonderfully well within one f-stop range. R zooms are actually great, but I have some doubts that you can find an R lens as good as 55-135 APO for a price worth paying.


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#11 rafael_macia

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Posted 21 June 2017 - 01:52

I will have to investigate the floating ISO setting. Thank you for that ..

I shoot manual exposure and manual focus exclusively. Also,I am only shooting short 20-30 second clips, I should mention that.

 

On a recent shot, using the 21-35 Vario Elmar 3.5-4  (a blister sharp lens !) 

I began the shot static at 21mm then zoomed in to about 30mm The overall exposure darkened slightly.    Not much.      Probably the ½ stop of the variable aperture.

I don't care for the darkening effect, I find the uneven exposure of the clip distracting.

The next person might not notice the darkening ....  but believe me    it is there.

Hopefully the floating ISO can counteract the darkening ?

thanks guys!


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#12 LD_50

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Posted 21 June 2017 - 03:53

Floating ISO is for the native lenses to counteract exposure changes when you zoom and the variable aperture changes with focal length.

#13 Irakly Shanidze

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Posted 21 June 2017 - 06:34

Floating ISO is for the native lenses to counteract exposure changes when you zoom and the variable aperture changes with focal length.

 

It works with T lenses too. 



#14 earleygallery

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Posted 21 June 2017 - 08:05

also... you might want to consider using Leica T lenses for 4K video instead of Sigma. Just so you can actually get what Leica SL is really capable of :)


Sigma have made lenses for Leica. The T lenses are made by an unknown 3rd party for Leica.

#15 Irakly Shanidze

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Posted 21 June 2017 - 09:27

Sigma have made lenses for Leica. The T lenses are made by an unknown 3rd party for Leica.

 

It does not really matter who makes what. What matter is how pictures look. Apparently, Leica learned the lesson with Vario-Elmar-R 28-70/3.5~4.5



#16 rafael_macia

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Posted 21 June 2017 - 12:16

So the floating ISO will work in manual setting?

If it will, I would pick up the 11-23 T lens along with the other T lenses.

thanks !


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#17 ramarren

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Posted 21 June 2017 - 20:18

So the floating ISO will work in manual setting?

If it will, I would pick up the 11-23 T lens along with the other T lenses.

thanks !

 

 

Yes ... actually, Floating ISO is ONLY applicable to manual exposure using "wide open" aperture with native-mount zoom lenses. That's the only time the condition it is designed to correct can take place, and is most important for video work to eliminate the darkening as you do a zoom-in shot, specifically. Its whole purpose is to counteract the fact that "wide open" changes as you zoom between two set limits; Gloating ISO overrides a fixed ISO setting specifically for that situation. 

 

It can't work with R lenses, or any other adapted lens, because the SL body has limited information about or no control of the lens aperture, and also limited information about the zoom setting. 


Edited by ramarren, 21 June 2017 - 20:18.

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#18 rafael_macia

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Posted 22 June 2017 - 01:02

Ok. so in short it is only useful when shooting wide open,  ? .......(which I never do).

and it only works with Leica SL/T lenses?

 

thank you !


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#19 ramarren

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Posted 22 June 2017 - 02:00

Ok. so in short it is only useful when shooting wide open,  ? .......(which I never do).

and it only works with Leica SL/T lenses?

 

thank you !

 

 

Yes, it is a feature specific to the use of Leica SL and T lenses on the SL body, using them wide open and with manual exposure.

 

I only mentioned it because you dissed the T and SL lenses since they weren't 'constant aperture'. In post #9, I said, in part: "...The variable aperture limitation should only impact you if you are shooting at wide-open aperture setting. I can't imagine shooting wide open for video in any scene where I also need to do coordinated focal length changes with the motion ... "

 

Floating ISO takes care of the "manual exposure, shooting wide open in video" problem. If you set to any aperture at or smaller than the smallest 'wide open' setting for a given lens, you should see no exposure drift as you zoom anyway, with any variable-maximum-aperture lens. 



#20 Irakly Shanidze

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Posted 22 June 2017 - 04:10

Not necessarily wide open, but at any aperture that will be too wide for the longer focal lengths when zooming in. For instance, you set ISO to 200 and aperture of a 18-56 T zoom to f/4 on the wide end and then zoom in all the way to 56mm for which the maximum aperture is f/5.6. To compensate for one-stop loss, the camera will bump ISO to 400.

 

If you set your initial aperture to, say, f/8 and then zoom in, the camera will keep it at f/8, and no ISO change is necessary.


Edited by Irakly Shanidze, 22 June 2017 - 04:11.



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