Can anyone work this out for me please (aperture equivalent )?

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Iiyama

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Ok, I try to write this as clearly as I can, to get across a calculation I cant find the answer for!


At present I use a 12-40 2.8 zoom on an Olympus EM-1 MFT camera. Im considering a move to Fuji that uses a APS-C size sensor. The Fuji XF 18-135mm f/3.5-5.6 lens has caught my eye. However it clearly has a different maximum aperture.


As its using a larger sensor which i understand has a crop factor of 1.5 what is its equivent aperture to my Oly 2.8?


Why do I ask? Well I love the Oly 2.8 DoF and low light capability. However, I fancy a system change and the longer focal length of this lens appeals. But I dont want to get it and find i need to use high ISO or a flash in situations where the Oly works fine.


Any guidance appreciated.
 
an f stop is an f stop. f/2.8 is f/2.8 if the lens is put on a crop sensor, a full frame sensor, or a 10x8" plate camera. (the f number is basically, the Ratio between the lens focal length and the diameter of the aperture - so if you've got a 50mm focal length lens, when it's set to f:2.0 the aperture is 25mm in diameter - 50:25 or 2:1. If the aperture is set to f:4.0 on the same lens, the hole will close up to 12.5mm diameter - 50:12.5 or 4:1. The reason that the aperture is expressed as a ratio, is so that the f:numbers ARE consistent across focal lengths and / or different sensor or film sizes... this used to be far more "interesting" before the digital era, and everyone started calling a sub-miniature form factor (35mm) as being "Full Frame" - whole plate used to be 6½"×8½" - and 10"x8" film and larger was not uncommon...

the only material difference between say a full frame and a crop sensor lens is the size of the "image circle" that the lens will project light onto at the rear.
 
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TheBigYin said:
an f stop is an f stop. f/2.8 is f/2.8 if the lens is put on a crop sensor, a full frame sensor, or a 10x8" plate camera.

the only material difference between say a full frame and a crop sensor lens is the size of the "image circle" that the lens will project light onto at the rear.
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Thanks for the reply. So it's the focal length equivalent that varies with sensor size not the aperture? I thought the aperture dof also changed.
 
f2.8 will always be f2.8, cropped or not. As also f/3.5-5.6 will always be f/3.5-5.6

The number is purely an expression of the ratio of focal length against 'hole' or aperture .... 25mm opening against 50mm focal gives f2.0

It only becomes an issue if you increase the barrel length or the distance from the film plane using extension tubes. There is also a compensation factor you need to recognise when using a converter.

ETA - slow typist! :)
 
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Aperture is aperture, so f2.8 will gather 4 x as much light as f5.6 whatever camera/system you use. In simple terms (without getting into the whole perspective/subject distance/effective focal length discussion) DOF does change depending on the sensor size, essentially the larger the sensor the smaller the DOF. With crop/APS-C you approximately lose 1 stop DOF compared to FF (so f2.8 on crop will more or less look like f4 on FF), and m4/3 you lose 2 stops DOF compared to FF (so f2.8 on m4/3 looks like f5.6 on FF). So when comparing Fuji to M4/3 there will be approximately 1 stop difference in DOF, so F2.8 on your Olly will look like F4 on the Fuji.

As I say this is a simplistic way of looking at things, and the difference isn't exactly a stop but if you think of it like this you won't go far wrong imo.
 
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Iiyama said:
I thought the aperture dof also changed.
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the Aperture DoF will be the same - AT THE SAME f:stop.... so, the Fuji XF 18-135mm f/3.5-5.6 will give the same DoF as your 12-40 2.8 - provided the 12-40 is set to the same f: stop as the 18-135 is. Obviously, a f/3.5-5.6 can't shoot at f:2.8... but if you stop your existing lens down to f3.5-f4.5 or so, it should be identical to the wider end of the new lens.
 
DoF changes, exposure doesn't. Simples.

Easiest to think about it in FF terms, multiply the m4/3 by 2 and the Fuji by 1.5 and compare them thus.

edit: and I assume you know enough to realise that the f/5.6 of the Fuji lens is slower than the Olympus from an exposure point of view so therefore you might have to bump up ISO.
 
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snerkler said:
So when comparing Fuji to M4/3 there will be approximately 1 stop difference in DOF, so F2.8 on your Olly will look like F4 on the Fuji.
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Thank you to all for the quick and very helpful replies. It is the point highlighted that I was really wondering but I was not clear in my original post. So I cancelled my lens order thinking the Fuji would be significantly slower.
 
Iiyama said:
Thank you to all for the quick and very helpful replies. It is the point highlighted that I was really wondering but I was not clear in my original post. So I cancelled my lens order thinking the Fuji would be significantly slower.
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Snerkler is right. Sensor size drives a lot of changes, including both the field-of-view ('effective' focal length, if you like) and also depth-of-field. Use the crop factor, that relates everything back to full-frame, ie 1.5x on Fuji, and 2x on M4/3. It applies to both focal length and f/number. Shooting from the same position, these focal lengths and apertures will all produce an image that is identical in terms of a) framing, b) perspective, and c) depth of field.

Full frame, 100mm f/5.6
Fuji 1.5x, 67mm f/3.7 (in round numbers, very close to f/4)
M4/3 2x, 50mm f/2.8

For exposure purposes though, the f/number remains constant so adjustments must be made to shutter speed or ISO for correct exposure.
 
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HoppyUK said:
Snerkler is right. Sensor size drives a lot of changes, including both the field-of-view ('effective' focal length, if you like) and also depth-of-field. Use the crop factor, that relates everything back to full-frame, ie 1.5x on Fuji, and 2x on M4/3. It applies to both focal length and f/number. Shooting from the same position, these focal lengths and apertures will all produce an image that is identical in terms of a) framing, b) perspective, and c) depth of field.

Full frame, 100mm f/5.6
Fuji 1.5x, 67mm f/3.7 (in round numbers, very close to f/4)
M4/3 2x, 50mm f/2.8

For exposure purposes though, the f/number remains constant so adjustments must be made to shutter speed or ISO for correct exposure.
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This^

It looks much more complicated than this if you start doing the full technical explanations, but this is all the info you need and simply explained.

Back to the original post, I think that lens looks less suitable both in IQ and DoF.
 
Phil V said:
Back to the original post, I think that lens looks less suitable both in IQ and DoF.
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Yes, the more I read the less convinced I am. I was considering changing systems and got offered a reasonable price to move to Fuji. I have no issues with the quality of the XT-1 but its making a comparative lens choice after being with MFT for so long. My main weapons of choice that suit my shooting style on MFT are the 45mm 1.8 and my 12-40 pro.
 
Iiyama said:
Yes, the more I read the less convinced I am. I was considering changing systems and got offered a reasonable price to move to Fuji. I have no issues with the quality of the XT-1 but its making a comparative lens choice after being with MFT for so long. My main weapons of choice that suit my shooting style on MFT are the 45mm 1.8 and my 12-40 pro.
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It is probably the form factor of the 4/3 system cameras that allows either relative small sized lenses or the relative large aperture in compact size that appeals to you, when compared to the APS fuji alternative. However there are advantages in the fuji offerings, it is not simply a matter of style.
If you find these differences unimportant to you, then a change is just an exercise in spending cash.
 
Terry, interesting point. One of the things that appeals to me with the Fuji is that the colours appeal and less noise at highr ISO.
 
Iiyama said:
Terry, interesting point. One of the things that appeals to me with the Fuji is that the colours appeal and less noise at highr ISO.
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Do you shoot raw?

I ask because I have MFT and have taken a look at Fuji a couple of times but have decided not to swap systems as I don't see a great image quality advantage for the Fuji. Fiddle with your images in the raw converter of you choice and surely you can get colours you like from MFT? And of course MFT has some very nice and very compact and light lenses.
 
woof woof said:
Do you shoot raw?

I ask because I have MFT and have taken a look at Fuji a couple of times but have decided not to swap systems as I don't see a great image quality advantage for the Fuji. Fiddle with your images in the raw converter of you choice and surely you can get colours you like from MFT? And of course MFT has some very nice and very compact and light lenses.
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Thanks Alan for the reply. I tend to shoot JPEG. However, this afternoon Im trying some Photoshop Tutorials to see what I can do and so far "proper" use of post processing appears to be helping improve my images. I shot my daughters wedding abroad in September and I was happy with most of the images apart from some strange skin artefacts that exaggerated poor skin or sunburn! However, when I looked at the Pro photographers images shot full frame they appeared to suffer a similar issue!

GAS is a terrible thing for us photographers.
 
The fuji lens you chose to compare with your oly 12-40 f2.8was the fuji 18-138 f3.5-5.6 these are entirely different comparable focal lengths.
in Ff terms it is 24-80 against 27-203mm
More equal would be the fuji 16-55 f2.8 which is the FF equivalent of 24-84.....almost identical.
or perhaps better for you the 18--55 f2.8 f4 FF equivalent 27-84 as this lens has OIS and f4 at the long end is no real problem.
 
Why did this become a discussion on FOV/DOF equivalence? That wasn't the question, and IMO it's a rather trivial concern unless you tend to do only one thing and want only one result/change.

The question was in regards to low light performance and avoiding higher ISO's. Putting it into "equivalence" makes it seem like the larger format will require a smaller aperture, a higher ISO, and have lower performance in low light; when that is actually backwards. In terms of the low light performance, aperture is aperture and a larger sensor will perform better.
 
sk66 said:
Why did this become a discussion on FOV/DOF equivalence? That wasn't the question, and IMO it's a rather trivial concern unless you tend to do only one thing and want only one result/change.

The question was in regards to low light performance and avoiding higher ISO's. Putting it into "equivalence" makes it seem like the larger format will require a smaller aperture, a higher ISO, and have lower performance in low light; when that is actually backwards. In terms of the low light performance, aperture is aperture and a larger sensor will perform better.
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Iiyama said:
As its using a larger sensor which i understand has a crop factor of 1.5 what is its equivent aperture to my Oly 2.8?

Why do I ask? Well I love the Oly 2.8 DoF and low light capability.
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sk66 said:
Why did this become a discussion on FOV/DOF equivalence? That wasn't the question, and IMO it's a rather trivial concern unless you tend to do only one thing and want only one result/change.

The question was in regards to low light performance and avoiding higher ISO's. Putting it into "equivalence" makes it seem like the larger format will require a smaller aperture, a higher ISO, and have lower performance in low light; when that is actually backwards. In terms of the low light performance, aperture is aperture and a larger sensor will perform better.
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The OP did make reference to DOF too, although appeared to prioritise the light gathering (y)
 
snerkler said:
The OP did make reference to DOF too, although appeared to prioritise the light gathering (y)
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It's a question worth asking but personally I find the sums easy enough to do using 35mm FF as a reference.

Exposure remains the same across formats (for the same aperture) so there's a possible advantage for the MFT and f2.8 there. I'm not sure how this will relate to image quality as you'd think that the Fuji would offer slightly better image quality but it may need a higher ISO which could negate any supposed advantage.

When looking at DoF, as the OP seems also to be doing...
MFT 2.8 x 2 (crop factor) = f5.6.
Fuji at the short end 3.5 - 5.6 = 3.5 x 1.5 = f5.25, at the long end 5.6 x 1.5 = f8.4.
So at the longer end the Fuji would lose out here a bit due to the variable aperture.

As I mentioned above, I've looked a Fuji a few times and have stared at raws on my screen and haven't seen a lot of clear water between Fuji and MFT. Also, a few of things do tend to put me off Fuji... the relatively low (these days...) max ISO available when shooting raw and the max mechanical shutter speed limit of 1/4,000. These things matter to me. In addition personally I think that the Fuji + lens package is leaving MFT behind (size wise) and challenging an A7 (depending what lens you fit) and IMO the A7 wins here on image quality.

So for me a Fuji +lens is probably going to be bigger than MFT whilst offering maybe only a slight if any image quality improvement and if going for a bigger than MFT CSC I'd rather reach for my A7 and see what is to me a more significant jump in image quality. On balance I think I'd only jump to Fuji if I thought I simply must have manual aperture and shutter dials above all else.
 
IMHO, DOF due to aperture is a fairly minor concern. What you are usually concerned with is not actually the DOF, but rather the treatment of the OOF sections. In that regards framing, FL, BG control/selection, and distances all matter a whole lot more than a couple of stops of aperture.
I can take two images with the same subject composition and DOF, and I can blur the BG to nothing in one or make it distracting in another.

I get that aperture is useful and a "creative choice." But IMO it shouldn't be the "first choice" for controlling the BG... it's the last choice when you have no other options.
 
sk66 said:
IMHO, DOF due to aperture is a fairly minor concern. What you are usually concerned with is not actually the DOF, but rather the treatment of the OOF sections. In that regards framing, FL, BG control/selection, and distances all matter a whole lot more than a couple of stops of aperture.
I can take two images with the same subject composition and DOF, and I can blur the BG to nothing in one or make it distracting in another.

I get that aperture is useful and a "creative choice." But IMO it shouldn't be the "first choice" for controlling the BG... it's the last choice when you have no other options.
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I assume you're referring to using different focal lengths and therefore camera to subject distances?
 
snerkler said:
I assume you're referring to using different focal lengths and therefore camera to subject distances?
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Yes, as well as choosing the BG and BG distance...

I think this is a very common mistake... *nothing* is as important as BG selection/control. You really can't blur a distracting BG effectively/easily w/ aperture (you just make the distractions larger). Granted, BG selection/control may not be an option... but it is a lot more often than many seem to consider.
 
sk66 said:
Yes, as well as choosing the BG and BG distance...

I think this is a very common mistake... *nothing* is as important as BG selection/control. You really can't blur a distracting BG effectively/easily w/ aperture (you just make the distractions larger). Granted, BG selection/control may not be an option... but it is a lot more often than many seem to consider.
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You could argue that you're altering composition by changing the background distance though :p Joking aside though you're right, there is a lot more to consider with subject isolation/background blur.
 
sk66 said:
IMHO, DOF due to aperture is a fairly minor concern. What you are usually concerned with is not actually the DOF, but rather the treatment of the OOF sections. In that regards framing, FL, BG control/selection, and distances all matter a whole lot more than a couple of stops of aperture.
I can take two images with the same subject composition and DOF, and I can blur the BG to nothing in one or make it distracting in another.

I get that aperture is useful and a "creative choice." But IMO it shouldn't be the "first choice" for controlling the BG... it's the last choice when you have no other options.
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Love the fact you say your not changing the composition when clearly that is the main thing your changing if your shifting the background! I see how this is an option if you are on a pro shoot but for most hobby photographers snapping away at friends and family it really isn't!
 
a1ex2001 said:
Love the fact you say your not changing the composition when clearly that is the main thing your changing if your shifting the background! I see how this is an option if you are on a pro shoot but for most hobby photographers snapping away at friends and family it really isn't!
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Depends on if the BG is important to the image... I was speaking of subject composition. The "option" doesn't depend on pro vs hobbyist, it's part of the difference between "making" a picture and "taking" one.
 
I thought it was a troll thread but I've met Iiyama in person in Marks & Spencer's carpark,
which puzzled me 'cos the question is about whether a 'travel zoom' on APS-C will give similar DOF to the short bright Pro zoom on m4/3rds.
At 40mm for example the Olympus will give a shallower DOF (wide-open) but the framing will be more similar to the Fuji at (off the cuff) 60mm-ish.
Still the restricted aperture of the travel zoom will give broader DOF and a lower quality image,
and in low light the contest is over : E-M1 wins.
In my opinion the Fuji X-series are best with their high-quality bright primes.
 
I've owned a Fuji APS-C camera alongside an M43 camera, and in real life usage the Fuji has a superior sensor if you need to do pp. At the time I was comparing an X-E1 with E-PL5. The Fuji had better dynamic range and lower / nicer noise in low light. Both systems have their merits though and the M43 gear is really very portable indeed :)
 
manualfocus-g said:
I've owned a Fuji APS-C camera alongside an M43 camera, and in real life usage the Fuji has a superior sensor if you need to do pp. At the time I was comparing an X-E1 with E-PL5. The Fuji had better dynamic range and lower / nicer noise in low light. Both systems have their merits though and the M43 gear is really very portable indeed :)
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Useful info. Unfortunately when I was looking DXOmark had no sensor scores for the XE1 but I found this which said DR wasn't as good as Olympus RAW files (EM5 essentially the same sensor as the EPL-5)

http://www.techradar.com/reviews/ca...gital-slrs-hybrids/fuji-x-e1-1094565/review/5


What were you comparing JPEG or RAW?
 
manualfocus-g said:
Those techradar results don't look right to me. Check out the nex-7 and e-m5 results at Dxomark to see what I mean. I always shoot raw by the way :)
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DXO does look slightly different yeah, but the Olly holds its own still. Wonder why DXO mark don't score Fuji?

Screen%20Shot%202016-01-18%20at%2008.47.01_zpshgarwnlr.png
 
It's an x trans thing. The sensor is likely to be the same as that of the Nex-6 though. I think!

The Oly does have a very good sensor BTW, which is way better than the previous generation of sensor. Everything is relative though, and I found it easier to work with the Fuji files.
 
manualfocus-g said:
It's an x trans thing. The sensor is likely to be the same as that of the Nex-6 though. I think!

The Oly does have a very good sensor BTW, which is way better than the previous generation of sensor. Everything is relative though, and I found it easier to work with the Fuji files.
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Thanks. I think I'm going to have to have a Fuji one day, they have a certain lure ;)
 
Ulfric M Douglas said:
I thought it was a troll thread but I've met Iiyama in person in Marks & Spencer's carpark,
which puzzled me 'cos the question is about whether a 'travel zoom' on APS-C will give similar DOF to the short bright Pro zoom on m4/3rds.
At 40mm for example the Olympus will give a shallower DOF (wide-open) but the framing will be more similar to the Fuji at (off the cuff) 60mm-ish.
Still the restricted aperture of the travel zoom will give broader DOF and a lower quality image,
and in low light the contest is over : E-M1 wins.
In my opinion the Fuji X-series are best with their high-quality bright primes.
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Hi Ulfric :)
My initial question was not clear or badly written. It came about because I was confusing myself (or trying to convince myself) that the travel zoom would be adequate for my needs. Not my brightest photography moment once I read the comments and thought about it more. Im still very tempted to move to Fuji but.....
 
Ulfric M Douglas said:
and in low light the contest is over : E-M1 wins.
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Having owned both an EM-1, X-Pro1 & XT-1 I can confirm with certainty that your talking a load of charlie horrocks, The Em-1 is way worse for noise at even moderate ISO's than the X-Pro1, in fact I limited myself to up to ISO 800 only as after that the iQ became unusable for me, with the X-Pro1 I can comfortably shoot at ISO 3200 without issue so the slight advantage of the lens aperture on the Oly 12-40 is negated by the poorer iQ of the EM-1 when compared to the Fuji's.
Yes you've guessed it, the EM-1 was sold, the X-Pro1 kept and I've never regretted it for a second. I'm not a fanboy and not brand loyal, but if something works for me I'll stick with it.

Iiyama said:
Hi Ulfric :)
My initial question was not clear or badly written. It came about because I was confusing myself (or trying to convince myself) that the travel zoom would be adequate for my needs. Not my brightest photography moment once I read the comments and thought about it more. Im still very tempted to move to Fuji but.....
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I think your getting yourself too wrapped up in technical details my friend, Lets look at the lenses first, so currently your using a 12-40mm F2.8 so its FF equivalent including DOF equivalency would be a 24-80mm F5.6, now I think the ideal lens from the fuji range would be a 18-55 f2.8-f4 so in FF terms thats a 27 - 82.5mm f3.2 - F4.5 (I think) so in real terms its slightly faster/shallower depth of field than the 12-40mm.
Now please don't make the mistake of thinking the 18-55 is just a cheapo kit lens, its not, its a very sharp and capable lens in its own right.

My advice would be to find someone near you who will let you try the camera/lens you want and see how you feel about the results.
 
Jeeze I hate these equivalence discussions... In what world is a 55/4 lens "faster" than a 40/2.8 lens?

Make everything as equivalent as you want/can and the net result is; when you double the sensor size (4/3 > APS > FF) you get ~ 1 stop less DOF... for better or worse.
Probably 70% of the time one stop is negligible, and 90+% of the time one stop won't make/break an image. And if it is enough to ruin an image, you were already on the ragged edge to start with.
 
Ulfric M Douglas said:
I thought it was a troll thread but I've met Iiyama in person in Marks & Spencer's carpark,
which puzzled me 'cos the question is about whether a 'travel zoom' on APS-C will give similar DOF to the short bright Pro zoom on m4/3rds.
At 40mm for example the Olympus will give a shallower DOF (wide-open) but the framing will be more similar to the Fuji at (off the cuff) 60mm-ish.
Still the restricted aperture of the travel zoom will give broader DOF and a lower quality image,
and in low light the contest is over : E-M1 wins.
In my opinion the Fuji X-series are best with their high-quality bright primes.
Click to expand...
The EM1 suffers a bit with noise, the EM10 and EM5 are better, and I would expect any newish APS sensor to be better than these two. Granted it's pretty negligible depending on which you're comparing.
 
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