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02-23-2015, 11:08 PM   #181
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QuoteOriginally posted by Class A Quote
An FF sensor has a larger surface to collect light with, but unless you use a faster lens, the same total amount of light that would have hit the APS-C sensor has to be spread over the larger FF area. This reduces the light intensity, i.e. light per square mm, or in other words the exposure..

Bizarre thinking.

02-24-2015, 12:16 AM   #182
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QuoteOriginally posted by clackers Quote
Bizarre thinking.
No, just the plain truth.

If you dig into the topic, you'll see it for yourself.

Note (see below) that I'm of course assuming an "apples to apples" comparison and hence different lenses must be used on different formats. Perhaps that comment alone resolves the "bizarreness"?

If not, maybe this helps: Falk Lumo: LumoLabs: Camera equivalence
Or this: Equivalence

Last edited by Class A; 02-24-2015 at 01:15 AM.
02-24-2015, 12:19 AM   #183
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QuoteOriginally posted by jhmos Quote
Did you mean with different lenses?
Yes.

I implied "comparing the same images", which implies different lenses for the different formats. To make a meaningful comparison, you need to capture the same scene (same AOV) but also from the same distance to the subject. This enforces, that the larger format camera uses a longer lens (which makes sense because when you blow up the sensor, you have to "blow up" the lens as well to keep things equivalent).

With " If I try the same full frame lens on a APS-C body or a full frame one, the light intensity at any point on the frame is going to be the same (apart for vignetting). " you are absolutely correct, but using the same lens on two different formats will always produce different images -- even if you try to account for the different framing by changing the distance to the subject -- so in order to make meaningful comparisons between different formats, the focal lengths used must always be different (by the crop factor between the formats).

Last edited by Class A; 02-24-2015 at 01:13 AM.
02-24-2015, 12:25 AM   #184
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QuoteOriginally posted by starjedi Quote
If there is an aps-c only K mount, the apps-c lens you mentioned should be possible to make with a similar size and weight.
I did not say that the listed lenses were impossible on APS-C. I said they don't exist, which is undeniably true.

QuoteOriginally posted by starjedi Quote
Theoretically if there is a high quality speed booster with proper aps-c mount, you can even use the ff lens to achieve the goal. No magic.
Yes, you could use a speed booster with the respective loss in quality.

And, yes, there is no magic.

But there are economics at play and it would be prohibitively expensive to produce a 21mm f/1.2 for APS-C (with the low tolerances required for the smaller format). A 31mm f/1.8 for FF, on the other hand, can be manufactured for reasonable money. The FA 31/1.8 isn't cheap, but for instance the Sigma 28/1.8 is very affordable. It is an FF lens and its APS-C equivalent -- a 19mm f/1.2 -- would also be very expensive.

02-24-2015, 12:36 AM   #185
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QuoteOriginally posted by jsherman999 Quote
Hi Class A, Either you have this swapped or I'm simply confused by your wording (possible.)
Hi jsherman999,

sorry for the confusion.

I mistakenly read normhead's "narrower" as "deeper" because I'm used to the term "shallower" (as opposed to "narrower") and hence thought he meant to express the opposite of "shallower".

That was clearly my mistake and if you read "narrower" as "shallower" then my post doesn't make sense. I edited my post, replacing all "narrower"s with "deeper"s and now it says exactly what you are saying. I meant to say "deeper" all along, just used the wrong word, because I tripped over normhead's use of "narrower". Still completely my fault, though.
02-24-2015, 01:01 AM   #186
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QuoteOriginally posted by normhead Quote
Funny, I once shot a small flower with a ruler, a 50mm lens to represent the FF camera and a 35 on 16 a K-5, to represent the APS-c, at the same settings and used the same framing, and got twice as much DoF with the 35 from exactly the same tripod mount position and ƒ-stop.
First, apologies for using "narrower" when I meant "deeper". Since you didn't use the common "shallower" I thought you meant the opposite of "shallower", which is deeper. Sorry, for getting mixed up.

However, your example does not make sense.
  1. You cannot "represent the FF camera" by just sticking a longer lens on an APS-C camera. The sensor size must grow as well. You could have simulated a four-thirds camera (to compare it to APS-C), by cropping a four-thirds portion out of the APS-C frame.
  2. Changing the distance to achieve the same framing is not a basis for a good comparison. By changing the distance, you also change perspective, i.e., you create a different image with different foreground/background proportions, and different DOF properties. The proper way to achieve the same framing is by using different focal lengths (and different sensor sizes).
  3. Why don't you visit a DOF calculator some time and change the sensor size in addition to the focal length (the equivalent APS-C focal length is closer to 33mm than to 35mm, BTW) and verify the "claims" that jsherman999 and I are making?

QuoteOriginally posted by normhead Quote
So, I'm not sure what you just said up there but it doesn't apply to my experience with real world shooting.
What I said -- which is much easier to read after I replaced "narrower" with "deeper" (which it always was intended to mean) -- is in accordance with physics, DOF calculators, and properly conducted experiments.

QuoteOriginally posted by normhead Quote
And why would you do that?
I would never use the same lens on two different formats with the same settings, unless I wanted to produce two completely different images.

So I agree with you, the thought experiment does not have much merit. The only reason I did it, was to make sense of your statement "Shooting FF means narrower depth of field" while misreading "narrower" as the opposite of "shallower".

Indeed, there is a situation when FF yields a deeper DOF, which is when you use the same lens on both formats and keep the same settings. That's the only reason as to why I brought this scenario up. My bad for not catching your true intent.

BTW, the statement "Shooting FF means shallower depth of field" (which is what you meant) is not true either. You can always stop down an FF lens, so that you get the same DOF as with an APS-C camera. The only exception to this rule is when you run out of f-ratios, say at "f/22" or so. You cannot replicate the DOF of a 33mm f/22 shot on APS-C with a 50mm f/33 shot on FF, because there is no 50mm lens that can be stopped down to f/33. However, such high f-ratios are not useful anyhow, as they dramatically limit resolution due to diffraction. You don't need more than ~2MP to capture the resolution of an f/22 image on APS-C. Such images are typically not worth taking, AFAIC.

QuoteOriginally posted by normhead Quote
You go for the shot you want with the equipment you have, and you pick the right lens for that format.
Sure, I 100% agree.

However, if you want to know whether it is worth spending money on FF equipment, it is good to have ways to make proper (fair) comparisons. That's when equivalent settings come in handy, otherwise you are just comparing apples to oranges.

QuoteOriginally posted by normhead Quote
It sounds an awful lot like..." if you don't agree with what I say , I can think of some stupid scenario where I'm right and you're wrong."
With all due respect, it was you who used that tactic when you grabbed "ISO 1600" out of thin air for the FF camera and then argued that high ISO values decrease dynamic range, etc. Clearly, the correct value to pick was "ISO 225" and picking anything higher only serves to drive home a point (for which no proper argumentation exists).

I never manufactured any examples to make APS-C look bad. I only state facts supported by physics and practice.

Last edited by Class A; 02-24-2015 at 01:08 AM.
02-24-2015, 04:49 AM - 2 Likes   #187
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I know folks who bring equivalence into arguments believe they are shedding light on the subject, but my experience is that they end up confusing everybody, but themselves.

In the end, each person needs to ask the question whether the format they are shooting allows them to get the framing they need and the depth of field they desire. If you have never thought to yourself: "I wish that my 50mm lens was f1," than that tells you something. Full frame is a trade off. You trade less depth of field for better high iso and dynamic range. If you can't deal with less depth of field, than you have to bump your iso to the point that it doesn't make a difference.

To me, a lot of the talk about the lack of faster lenses on APS-C is a red herring. Yes, they don't exist, but they don't exist because they aren't particularly needed by the average photographer. The things I shoot with my DA 15 don't really require f1.8 or f2. Even f4 doesn't give adequate depth of field for most landscapes. If you are shooting a lot of portraits at 16mm on APS-C, then you may feel differently.

I will just say again that I have seen many more photos spoiled by lack of depth of field, than ones in which a little extra depth of field destroyed the photo. Yes, you can stop down on full frame and yes, you can choose to shoot slower lenses as well, but then what's the point? You might just as well have stuck with APS-C.
02-24-2015, 06:01 AM   #188
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QuoteOriginally posted by Rondec Quote
I know folks who bring equivalence into arguments believe they are shedding light on the subject, but my experience is that they end up confusing everybody, but themselves.
Guilty! I confess, equivalency confuses me... Just another reason to go FF, so my 50 1.4 actually is a 50 1.4.


QuoteOriginally posted by Rondec Quote
To me, a lot of the talk about the lack of faster lenses on APS-C is a red herring. Yes, they don't exist, but they don't exist because they aren't particularly needed by the average photographer. The things I shoot with my DA 15 don't really require f1.8 or f2. Even f4 doesn't give adequate depth of field for most landscapes. If you are shooting a lot of portraits at 16mm on APS-C, then you may feel differently.

I will just say again that I have seen many more photos spoiled by lack of depth of field, than ones in which a little extra depth of field destroyed the photo. Yes, you can stop down on full frame and yes, you can choose to shoot slower lenses as well, but then what's the point? You might just as well have stuck with APS-C.
Funny that you take the DA 15 ltd as an example. I agree with you on the DOF part, no doubt. But 15mm + APS-C = horrible distortions. It's ok for landscapes, as long nothing resides in the far corners. As soon as any object is in there, it gets stretched. That problem is greatly reduced by using a ~21mm on an FF format camera...

02-24-2015, 06:08 AM   #189
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QuoteOriginally posted by Clavius Quote
Guilty! I confess, equivalency confuses me... Just another reason to go FF, so my 50 1.4 actually is a 50 1.4.



Funny that you take the DA 15 ltd as an example. I agree with you on the DOF part, no doubt. But 15mm + APS-C = horrible distortions. It's ok for landscapes, as long nothing resides in the far corners. As soon as any object is in there, it gets stretched. That problem is greatly reduced by using a ~21mm on an FF format camera...
Sure. But I shoot landscapes with 15mm and I don't shoot portraits with it. And 20mm isn't great for portraits on full frame by any means, either. For environmental stuff with people in the middle of the frame, both are probably OK, but it isn't their strong points. Beyond which, your "horrible distortions" aren't that bad. Photozone measures it at 1.4 percent, while the Canon 24mm f1.4 lens is measured at 1.35 percent distortion. How much difference is that .05 percent? Hard for me to say, but based on what you say, it is clearly visible in most real world situations.
02-24-2015, 06:14 AM   #190
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QuoteOriginally posted by Class A Quote
Changing the distance to achieve the same framing is not a basis for a good comparison. By changing the distance, you also change perspective, i.e., you create a different image with different foreground/background proportions, and different DOF properties. The proper way to achieve the same framing is by using different focal lengths (and different sensor sizes).
C'mon, this sort of thing is just breeding antagonism. Moving distances to get the same framing of the subject will be common practice and it's useful to understand what happens. I use a 100mm all the time for candid head shots, if I came upon a k-mount dslr tomorrow, I'm much more likely to use the same 100mm on it for head shots (from closer, so less candid unless I wear a cunning disguise) than I am to go out and find a 150mm lens.

Nether comparison is better than the other, they're just different (though I also don't understand how Norm's example is supposed to simulate a ff/aps-c DoF comparison). I beg of you to stop trying to enforce an 'apples to apples' comparison as you call it, it's A way to compare, not THE way.
02-24-2015, 06:52 AM   #191
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QuoteOriginally posted by Rondec Quote
Sure. But I shoot landscapes with 15mm and I don't shoot portraits with it. And 20mm isn't great for portraits on full frame by any means, either.
I wasn't talking about shooting portraits with 15 or 20mm. It's not just people that get stretched. You never have any objects in the corners? Trees that suddenly look chubby? Cars that look like stretch limo's? I always instantly notice it and it bothers me a lot.


QuoteOriginally posted by Rondec Quote
For environmental stuff with people in the middle of the frame, both are probably OK, but it isn't their strong points. Beyond which, your "horrible distortions" aren't that bad. Photozone measures it at 1.4 percent, while the Canon 24mm f1.4 lens is measured at 1.35 percent distortion. How much difference is that .05 percent? Hard for me to say, but based on what you say, it is clearly visible in most real world situations.
For me the noticable difference between UWA performance on APS-C and FF was the very reason to desire FF over APS-C.
02-24-2015, 07:02 AM   #192
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QuoteOriginally posted by Rondec Quote
I know folks who bring equivalence into arguments believe they are shedding light on the subject, but my experience is that they end up confusing everybody, but themselves.
If you pay attention though, 80% of the time equivalence has already been brought in to the discussion - and used incorrectly.

Nothing is more confusing (and potentially harmful to the wallet) than presenting it incorrectly.

.
QuoteQuote:
In the end, each person needs to ask the question whether the format they are shooting allows them to get the framing they need and the depth of field they desire.
Or the level of noise and DR they find acceptable.

QuoteQuote:

To me, a lot of the talk about the lack of faster lenses on APS-C is a red herring. Yes, they don't exist, but they don't exist because they aren't particularly needed by the average photographer.
Anyone who shoots an f/2.8 zoom a lot would disagree with you.

Or anyone who shoots any fast prime to squeak out the best SNR/DR available. That covers a lot of photography, and it's just a start

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02-24-2015, 08:08 AM   #193
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02-24-2015, 08:31 AM   #194
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QuoteOriginally posted by Clavius Quote
I wasn't talking about shooting portraits with 15 or 20mm. It's not just people that get stretched. You never have any objects in the corners? Trees that suddenly look chubby? Cars that look like stretch limo's? I always instantly notice it and it bothers me a lot.




For me the noticable difference between UWA performance on APS-C and FF was the very reason to desire FF over APS-C.
What lenses contributed to this decision? It's definitely something of interest.... but conclusive comparisons are hard to come by.
Since I picked up my Sigma 8-16 I haven't given this a thought.
02-24-2015, 08:38 AM   #195
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maybe the use of speed to mean physical aperture is the problem

QuoteOriginally posted by clackers Quote
Bizarre thinking.
It isn't bizarre, it just may be a different way of phrasing it than you're used to. Class A said:

"...An FF sensor has a larger surface to collect light with, but unless you use a faster lens, the same total amount of light that would have hit the APS-C sensor has to be spread over the larger FF area. This reduces the light intensity, i.e. light per square mm, or in other words the exposure.."

Using his 'faster' usage above, what this means is that if you shoot the following combos:

50mm f/2.8 FF
35mm f/2.8 aps-c

They have the same exposure (light intensity), but the FF lens in this case is 'faster' because it actually is using a larger physical aperture: 50 / 2.8 = 17.8mm, vs 35 / 2.8 = 12.5mm.

If you don't shoot the lens faster, i.e. maybe you wanted to get the same DOF as the aps-c combo, then your lenses will have the same physical aperture (speed) but the exposure will be less with the FF combo:

50mm f/4 FF
35mm f/2.8 aps-c

both = 12.5mm physical aperture



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