Apeture affecte from fulframe too APSC ?

[ropo54]

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Let me approach this in a different way.

 

I have a Leica SL601 with Leica SL 50 1.4. I'm quite happy with it.

 

I also have a CL with apsc sensor.

 

If I am wanting to shoot at 75 mm would I be content simply using the SL 50 1.4 on the CL, as compared to using a SL601 with the new SL75 f2?  (Aside from perhaps losing 1 stop of ISO range sensitivity?  Or, does that not occur because the lens is a 1.4).  

 

In other words, what would be the reasons to also acquire the Leica SL 75?

Edited February 1, 2018 by ropo54

[jaapv]

No ISO value loss.

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[wizard]

Using your SL 50 1.4 lens on the CL will give you a resulting image comparable with what you would obtain from using a 75mm lens on your Leica SL. And you will not lose 1 stop of ISO range, as f1.4 remains f1.4 on your CL.

 

Reasons for buying the new SL75 f2? Well, if you want to shoot 75mm on the FF Leica SL, there is no other way than buying a 75mm lens. Depth of field at the same aperture will be less with the SL75 f2 on the SL compared to the SL 50 1.4 lens on your CL, which may or may not be an advantage, depending on what you shoot and your own preferences. You will, however, lose 1 stop with the SL75 f2 over the SL 50 1.4 lens.

Edited February 1, 2018 by wizard

[Alberti]

There have been several thousand words on this topic. (and we have had the same questions when the M8 came out).

A picture to clarify the things - such as Jareds good post #42 - would do wonders. Such a picture would be worth 1000 words (but will generate some again too  ). 

 

Same lens example (1): As a drawing convention out of my memory, I used to have optics class at physics and the icon was an arrow (upside down on the film/sensor side); with two 'enlargements/sensor sizes' to get the arrow all the way fitting the frame, the distance has to vary if the same lens is used (smaller sensor, back off). "Images that look the same" means in this picture: the arrow touches both sides of the sensor; so the image is exactly the same as regards that aspect.

Or (2) use a wider lens (the 35/50mm example) and keep the same 'distance'.

 

Next the DoF can be compounded into these pictures.

This clarifies the F-factor (1.4 vs 2) to get also the same effect (circle of confusion) in the images. (like Lct's nice pictures of post #55 show). What is it we see in those examples in a schematic picture?

 

And finally the enlargement. Viewing the two files in the same enlargement (say 10x15 cm) means more enlargement for the smaller sensor to get the same print (and that has sort of nothing to do with the pixel count) if we think of a film size. Funnily if the two sensors have the same pixel count (24MP, 4000x6000) both files will look the same in image size (full arrow from the example); and from that point onward only the 400 dots per cm of the printer determines that the output is 10x15cm and the arrow is 10cm.

 

I'm not able to condense this all into the drawings right now, but they must exist already  First of all, my words and ideas will with 95% of confidence be confusing, but anyway I hope I give a clear overview of the purpose of such pictures.

 

ps I did not even bother to look at the video.

[Jared]

I think we're on the same page here. My argument was a scientifc one so to speak, taking into account the laws of optics and physics. Your argument is based on everyday practice, and I fully agree with what you have said. However, when discussing DoF between various sensor or film formats, I believe it is essential for people to understand some basics in optics, otherwise confusion is inevitable (and I am not talking about the circle of confusion here   ). Turning back to the OP's question whether a f2 35mm Summicron-M is still a f2 35mm Summicron-M if used on an APSC camera or rather turns into an f? 50mm lens, the answer clearly is that the lens stays as it is, a f2 35mm Summicron-M, as mounting it to another camera body will not have any effect on the lens. If the question would have been along the lines 'when I use a f2 35mm Summicron-M on my FF camera, do I have to use a different lens on an APSC camera to obtain the same image', well, then the answer would have been 'Yes, you need a different focal length to capture the same image from the same position, and since you have to use a different (read smaller) focal length, there will be an effect on DoF, too'.

 

 

Yes, I agree with this.  We are on the same page.

[frame-it]

Edited February 2, 2018 by frame-it

[Jared]

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Let me approach this in a different way.

 

I have a Leica SL601 with Leica SL 50 1.4. I'm quite happy with it.

 

I also have a CL with apsc sensor.

 

If I am wanting to shoot at 75 mm would I be content simply using the SL 50 1.4 on the CL, as compared to using a SL601 with the new SL75 f2?  (Aside from perhaps losing 1 stop of ISO range sensitivity?  Or, does that not occur because the lens is a 1.4).  

 

In other words, what would be the reasons to also acquire the Leica SL 75?

 

 

As far as whether you would still need the SL 75... That would depend entirely on whether you wanted to have a 75mm lens for your larger body.  If you don't mind shooting the 50mm SL lens on the CL camera, it should be very similar to what you would get with the 75mm on the CL.  But you'd have to use the CL camera instead of the SL.  If 75mm were a focal length I used often, I don't think I would like what you are proposing.  Big heavy lens/small camera <> match made in heaven.  If it's for occasional use?  Sure.  Should work fine.  No real downsides aside from ergonomics.

 

By the way, you wouldn't be giving up anything with regard to ISO.  You could shoot the 50mm on the CL with the aperture opened one stop wider for any given photographic situation, lower the ISO one stop as a result, and get the same noise results as you would on the SL.  At least in theory.  In practice?  One detector may be a little better or worse so this may not be exact.  Plus, the CL will be more demanding of the lens in the middle of the frame since the pixels are smaller, but more forgiving in the corners of the image since the corners are actually nowhere near the edge of the image circle produced by the lens.  Net result?  No way to be for sure if there were any subtle differences without trying.  They would definitely be subtle, though.

[Lonescapes]

Your 50 1.4 on APS-C will have the exact same DOF. It will just be longer focally (75), causing you to step back to capture the same perspective. Which means it will have just a hair deeper DOF than 75 f2, but will be basically identical.

[ropo54]

Your 50 1.4 on APS-C will have the exact same DOF. It will just be longer focally (75), causing you to step back to capture the same perspective. Which means it will have just a hair deeper DOF than 75 f2, but will be basically identical.

 

Thanks, Wizard, Jared and Lonescapes.

 

Aside from the ergonomic issues suggested by Jared,  then, it would seem there would not be much of a reason to consider the SL 75 purchase if DOF is "basically identical".   (Though, re-reading Wizard's note above, I'm not sure whether his comment  and Lonescapes' -- regarding DOF-- are meant to connote the same thing).

Edited February 2, 2018 by ropo54

[wizard]

Thanks, Wizard, Jared and Lonescapes.

 

Aside from the ergonomic issues suggested by Jared,  then, it would seem there would not be much of a reason to consider the SL 75 purchase if DOF is "basically identical".   (Though, re-reading Wizard's note above, I'm not sure whether his comment  and Lonescapes' -- regarding DOF-- are meant to connote the same thing).

 

Lonescapes proceeds from the assumption that if - using your 50 f1.4 lens on both cameras - you want to obtain the same image with both you Leica SL and CL, this requires that you have to step back when using the CL, simply because the 50mm lens used on the CL gives you a result, due to the CL's smaller sensor, which is equivalent to using a 75mm lens on your SL. To regain the 'same image' you would obtain with the 50mm  lens on the SL you will therefore have to step back with the CL (and, to be exact, the image will then not be quite the same, as the perspective will change once you start stepping back from your original location).

 

I was referring to the fact that what you seem to want is the result that a 75mm lens would give you on your SL. Two ways to get there: i) use your 50mm SL lens on the CL, or ii) buy a 75mm lens for your SL. The difference between i) and ii) is that when comparing shots of a given object taken at the same aperture, DoF will be lower with the 75mm lens (because of its longer focal length). As a rule, longer focal length always results - as long as the same aperture and distance to object are compared - in smaller DoF, irrespective of sensor or film size. Accordingly, as you are contemplating using a 50mm lens on the CL versus a 75mm lens on the SL to obtain, in both cases, the 75mm 'effect', DoF will be less with the 75mm lens.

Edited February 2, 2018 by wizard

[scott kirkpatrick]

Did anyone notice, in the video posted by Frameit (from the red moon), the crop sensor shot was the more successful one?

[Lonescapes]

Just read this:

 

http://admiringlight.com/blog/full-frame-equivalence-and-why-it-doesnt-matter/

 

FYI, don't mind the title and the bias against full frame it implies. He's just responding to the marketing hype around the words 'full frame.'

 

It's a very concise and accurate explanation of how photographic perspective and depth of field interact with focal length.

 

Ropo: What I meant by basically identical was this:

 

If you take your 50 1.4, put it on an APS-C camera, and back up far enough to frame the shot as if you were shooting it at 50 (not 75, which is your effective focal length), then it will give you the same depth of field, at the distance necessary to obtain identical framing, as a 50mm F2.1. So, in DOF terms, pretty much the same as 50 F2.

 

In other terms it will change a bit (perspective compression, for instance). But the difference between 75 and 50 in this respect, in terms of things that are not related to the behavioral effect of shooting longer lenses (e.g. where you choose to stand in relation to your subject as a result of the focal length)--these differences are small enough you won't notice much between the 50 and 75.

Edited February 2, 2018 by Lonescapes

[ropo54]

Wizard and Lonescapes: 

 

Thank you, again. (Btw, superb article explaining the issues!)

 

I apologize for being so obtuse, but I wanted to understand this from the theoretical point of view. For my purposes the small differences will make little difference and as many have suggested, it is best to just experiment with the each of the systems to become familiar with the results from the differing lenses.

 

Regards,

Rob

Edited February 2, 2018 by ropo54

[jaapv]

Just read this:

 

http://admiringlight.com/blog/full-frame-equivalence-and-why-it-doesnt-matter/

 

FYI, don't mind the title and the bias against full frame it implies. He's just responding to the marketing hype around the words 'full frame.'

 

It's a very concise and accurate explanation of how photographic perspective and depth of field interact with focal length.

 

Ropo: What I meant by basically identical was this:

 

If you take your 50 1.4, put it on an APS-C camera, and back up far enough to frame the shot as if you were shooting it at 50 (not 75, which is your effective focal length), then it will give you the same depth of field, at the distance necessary to obtain identical framing, as a 50mm F2.1. So, in DOF terms, pretty much the same as 50 F2.

 

In other terms it will change a bit (perspective compression, for instance). But the difference between 75 and 50 in this respect, in terms of things that are not related to the behavioral effect of shooting longer lenses (e.g. where you choose to stand in relation to your subject as a result of the focal length)--these differences are small enough you won't notice much between the 50 and 75.

Thank you for linking to this most excellent article.

[wizard]

Just read this:

 

http://admiringlight.com/blog/full-frame-equivalence-and-why-it-doesnt-matter/

 

...

 

Yes, thanks so much for bringing this very good article to our attention. In the article one may find the following statement:

 

This makes sense because smaller format cameras use shorter focal lengths for the same field of view, and therefore similar f-stops mean a smaller physical aperture size: less blur.

 

which is what I had tried to explain above.

[Lonescapes]

By the same author on perspective and compression:

 

http://admiringlight.com/blog/perspective-correcting-myth/

[Jared]

There have been several thousand words on this topic. (and we have had the same questions when the M8 came out).

A picture to clarify the things - such as Jareds good post #42 - would do wonders. Such a picture would be worth 1000 words (but will generate some again too  ). 

 

 

 

 

Your wish is my command!

 

Background/Methodology

• Comparison between:  35mm lens, APS-C camera, f/1.4 aperture, 1/125s exposure, ISO 800; 50mm lens, full frame camera, f/2 aperture, 1/125s exposure, ISO 1600
• Two images taken within a few seconds of each other under static lighting conditions
• Images taken in DNG format (Raw)
• APS camera used was Leica CL; full frame camera used was Leica M10
• Lenses used were 35mm Summilux-TL at f/1.4 and 50mm APO Summicron-M at f/2
• Both images taken from the same physical location (hand held, though, so slight variations in point of view)
• Point of focus was the left lapel button hole; both cameras were focused using the center of the frame and recomposing
• Images were brought into Lightroom where white balance was set manually using the "silver" portion of the arm rest as a neutral tone
• All noise reduction and sharpening was nominally disabled in Lightroom; no other adjustments were made to the image
• Both images were exported to Photoshop for resizing/cropping and JPG creation using sRGB color space at 100% quality with no other adjustments

Intent

To help people form an opinion as to whether "equivalence" holds for these two cameras and lenses, that is, whether 50mm/full frame/f2 is equivalent to 35mm/APS-C/f1.4 with regard to field of view, resolution, depth of field, and signal-to-noise ratio.  Note that because the 50mm lens was slower, a higher ISO setting was used on the full frame camera to get the same exposure.

 

First, here is the overall frame with the point of focus indicated.  I chose a subject that had plenty of fine detail and was oriented at roughly 45 degrees to the plane of focus to allow an easy comparison of depth of field.  Obviously, I am not suggesting that the photograph is intrinsically interesting or good, but I believe it does illustrate the concept.

 

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[Jared]

Now, here is the full frame from the M10...

 

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[Jared]

And the full frame from the CL...

 

Sorry these are in separate posts, by the way, but I wanted to leave the image quality high and that means file sizes were relatively big.

 

 

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[Jared]

Not perfectly identical fields of view due to the limitations of handholding and composing with an EVF vs a rangefinder, but it's reasonably close.

 

Now, here is a 100% crop of the point of focus from the M10...

 

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