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10-09-2014, 06:04 AM - 3 Likes   #16
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QuoteOriginally posted by marcusBMG Quote
Tony Northrup got similar responses. I (and he) never said that the focal length or aperture of the lens changes. I (and he) are saying that if you want to think in terms of full frame equivalence then its both aperture and focal length that need to be multiplied by the crop factor. And the fact is that many do - only yesterday I pm'ed a fellow forum member who had written that a classic 135mm f2.8 would give 200mm!! at f2.8!! And the fact is that many don't appreciate the effect on DoF..
Several flaws in the argumentation:
1) Insisting that different formats should have the same output and/or collect the same amount of light. This is wrong according to the theory of exposure. If it was correct a Pentax 645 should be compared to a cell phone. The theory of exposure is based on exposure (surprise). DOF doesn't enter into it.
2) Using one format as benchmark; usually FF, and directly or indirectly indicating at whatever DOF you get on that format at whatever aperture is the correct one or desired one which any other format must comply with. This is cheating. By this method only the properties of the reference format is used as benchmark. Whatever properties the smaller format has is ignored.This is only a one-sided biased opinion. Obviously, in order for two lenses to be DOF equivalent they both have to do the same. Ie an equivalent FF lens must be able to do what the smaller format lens does as well DOF-wise to be "equal". Such lenses do not exist. DOF equivalency between formats is a pipe-dream. And why only wide open at a certain focus distance? Why not compare DOF range and maximum DOF as well?
3) Pretending that DOF is only depending on aperture and equivalent focal lenghts. It isn't. It is dependent on aperture, focal lenght, focusing distances, and subject magnification. Ie lenses claimed to be DOF equivalent are patently not. Not even wide open.
Some may be surprised if they put "equivalent" lenses into a DOF calculator. For comperable lenses (eg prime vs prime, zoom vs zoom) you'll find that the smaller format lens usually has thinner minimum DOF than the larger. This is because it has larger maximum magnification.

In reality you loose one stop with FF compared to APS cause you have to shoot at one stop longer shutterspeed with FF at the same ISO for the same DOF.

Defining aperture form DOF is equally sensible as defining shutterspeed from motion blur.

The claim that thin DOF is the holy goal of photography is nonsense. In fact, 99,999% of all photograph ever taken, and I'm not even exaggregating, has DOF achievable with APS.
Insising that thin DOF is sole purpose of high speed in a lens is equally misguided.


Last edited by Pål Jensen; 10-09-2014 at 06:12 AM.
10-09-2014, 06:08 AM   #17
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In my opinion, it is maths that is applied wrong, and thus the result is not sound. Lets look at the example that was posted - 135mm f2.8. Put it on a crop sensor camera and you get the same field of view that a 200mm would give on a film camera. You switch to Av mode and f2.8. Both cameras, crop and film, will give you the same ISO and shutter speed. And if the bird is 10m away, the DoF will be the same depth in both cases. The difference is only the field of view, you get the same DoF, and the same brightness. Now, if the photographer goes mad and decides that "hey, I want to take this photo of the bird that is 10m away in such a manner, that the depth of field and field of view will be exactly the same as if I were using a film camera" then all sorts of settings will have to be changed. Aperture, focal length, ISO, shutter speed, distance from subject. And once you get the same depth of field and the same field of view, suddenly everything else will be different and the photo will look very different, even though it might have the same field of view and depth of field. The rendering, the blur, the noise will be different. But here is the kicker, it works both ways! If you take a full frame an try to imitate a crop sensor, you would again need to make all sorts of sacrifices and still end up with different final output! And if the photo we are imitating was taken with optimal settings, then the imitation will be sub-optimal.

Equivalence should be used only so that people switching between formats can understand things more easily. I know what 35mm looks like on crop, but I don't know what 55mm looks like on 645Z or 10mm on Q7. But if I do the equivalence multiplication, I can understand the approximate field of view with that focal length on that camera format. And I doubt I would ever need to know the equivalent DoF, and I doubt even more I would need the equivalent DoF and at the same time also equivalent FoV. This means the equivalence, as proposed in the original video, has a use only.. well, actually I don't know when it could be used in real world photography. A specific subgenre of portraiture? But even then, I am sure good portraits can be taken with formats other than full frame

Last edited by Na Horuk; 10-09-2014 at 06:17 AM.
10-09-2014, 06:11 AM   #18
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QuoteOriginally posted by Pål Jensen Quote
In reality you loose one stop with FF compared to APS cause you have to shoot at one stop longer shutterspeed with FF at the same ISO for the same DOF.
thank you
(and your other points are all good, except you imply I said against them which I didn't!!)

---------- Post added 9th Oct 2014 at 14:13 ----------

QuoteOriginally posted by Na Horuk Quote
Both cameras, crop and film, will give you the same ISO and shutter speed
Are you sure about that? See this Tony Northrup video from around the 8 minutes mark:

Last edited by marcusBMG; 10-09-2014 at 06:54 AM.
10-09-2014, 06:21 AM   #19
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While the math is correct, this only matters if you care about shooting wide apertures, in that case yes FF is cheaper. For light gathering purposes, a 70-200/2.8 in APSC really does act like 105-300/f2.8. There are alot of photographers that shoot mostly stopped down, they dont care if the DOF of 70-200/2.8 on APSC is like 105-300/4 on FF, since they dont shoot it wide open anyway.

If you shoot stopped down, APSC still has its advantages, it's smaller, gives you more DOF, and cheaper in the longer tele and extreme wide. Both format has its advantages so it's not as clear cut as you think it is. I love FF for the DOF control but it's not something all photographers appreciate.

QuoteQuote:
The claim that thin DOF is the holy goal of photography is nonsense. In fact, 99,999% of all photograph ever taken, and I'm not even exaggregating, has DOF achievable with APS.
+1, I shoot wide open alot but that's just because I prefer it, it doesnt mean it's necessary to make good photos.

QuoteQuote:
The assertion that, say, a 50mm f/2.0 lens on "full frame" would become a 75mm f/3.5 lens on APS-C is just plain wrong.
For the purposes of DOF control, this is actually true. Only that it's more like 2.8 rather than 3.5. Mounting a 28-75/2.8 on FF is like shooting an (nonexistent) 18-50/2 on APSC for DOF purposes only.. This is why lots of FF people aren't so hot on the Sigma 18-35, we already have lots of 28-70/2.8 for the longest time at the same price or cheaper.


Last edited by Andi Lo; 10-09-2014 at 06:43 AM.
10-09-2014, 06:40 AM - 1 Like   #20
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QuoteOriginally posted by Na Horuk Quote
The difference is only the field of view, you get the same DoF
No, you don't.


QuoteOriginally posted by Na Horuk Quote
Like Sigma with 18-35mm f1.8, or Fuji with 56mm f1.2, 23mm f1.4 and similar lenses.
THIS.

Exactly the point when people talk about equivalence - a smaller sensor *should* afford you some creative options for lens design. Pentax has some success with this in designing great pancake primes by the way.


It isn't irrelevant to talk about equivalence since it is universally understood that there is a "crop factor". Even Pentax implicitly acknowledges this with their zooms - the 50-135mm is curiously close to the old 80-200mm zooms. They fail to mention that 50-135 f/2.8 (a lens likely to be used wide open by the way) is more like a 75-200mm f/4, which isn't nearly as attractive a spec for the price.
10-09-2014, 06:47 AM - 1 Like   #21
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QuoteOriginally posted by carpents Quote
It isn't irrelevant to talk about equivalence since it is universally understood that there is a "crop factor". Even Pentax implicitly acknowledges this with their zooms - the 50-135mm is curiously close to the old 80-200mm zooms. They fail to mention that 50-135 f/2.8 (a lens likely to be used wide open by the way) is more like a 75-200mm f/4, which isn't nearly as attractive a spec for the price.
Only that fuji has outpentaxed pentax in that department (creative lens designs) in recent days :/ I think the last exciting one we got was DA 15. But I think pentax is on a good streak at the moment, and it can only get better I have hope.

Yeah I agree with that on DA 50-135. I don't think Pentax ever claimed that it's equivalent to 70-200/2.8 in DOF though, only that it's FOV equivalent to a 70-200. Also, for $1300 in FF you can only buy a f/4 version with SR, so it's not like the price is not competitive. I think it's a missed opportunity though because body SR is supposed to make the price of lenses cheaper!

If you decide to forgo SR you have more options though: (Tamron 70-200, Sigma 70-200, Nikon 70-200/2.8 v1/v2) for $700-800!! You can also pay some more dough and get 70-200/2.8 with SR Options are good

Last edited by Andi Lo; 10-09-2014 at 06:55 AM.
10-09-2014, 06:47 AM - 1 Like   #22
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QuoteOriginally posted by Andi Lo Quote
A 70-200/2.8 in APSC really does act like 105-300/f2.8 for light gathering purposes
No it doesn't. This is the deeper point.
How can a smaller sensor catch the same amount of light as a larger sensor. it can't and it doesn't.
I just went and took two pics at 200ASA with my 50mm f1.4 at f1.4 on my lumix g1 (2x crop factor) and my K-r, same shutter speed. pics came out the same. But the cameras are cheating. They are both set up internally to match the familiar ASA scale of brightness. In fact the G1 is producing a matching image off the smaller number of photons that are hitting the smaller sensor, in effect it is using a more sensitive ie a "faster" setting.

This is explained clearly by Northrup in this video: see from around 8 minutes on


UPDATE: NOT explained clearly see my later post (#109) commenting on his video, where I remark specifically on his failure to clarify the different consequences of less/more total light vs light intensity.

Sorry - confusion on this point was mine

Last edited by marcusBMG; 10-11-2014 at 06:39 AM.
10-09-2014, 07:01 AM - 1 Like   #23
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I've been thinking about this video. he does a little add for the manufacturers who support this nonsense Guess who i pushing this agenda? Nikon an Canon, probably the two biggest companies pushing full frame camera. Of course they want Full Frame to be the centre of the universe. Of course they don't want MF mentioned in the video. OF course they want to subvert the definitions of Aerture or ISO to fit their sales strategy. This man is a shameless shill and nothing more. Ever piece of good information he presents is polluted by his relentless Full Frame ideology.

After the trashing this video has received in other threads, the OP should be embarrassed he even posted it.

But since he didn't

Aperture is not defined by DoF. Read the wiki definition, I posted it in the last thread where this was posted. DoF is about DoF, and it's not measured in stops, it's measured in measures of linear units, anyone who wants to measure DoF in stops is trying to do a con job on you.

ISO is not about total light collected. The man in the video is simply lying. There was more difference in the amount of light collected by the "sensor" in film days when there were 8x10 film cameras and milota minoxs that were completely tiny, yet the ISO standard was adopted.. ISO hasn't been made obsolete by digital. The total amount of light captured by the film was never part of ISO. Again read the wiki entry. SO once again the author claims a term is irrelevant, that is still completely irrelevant. The brainwashing continues with his diagram where FF is the biggest sensor. What happened to MF? Oh, well that doesn't fit with the Full Frame superiority mindset so, it's conveniently left off.

This man is lying through his teeth. I just hope no one gets sucked in by this nonsense.

If you believe this stuff, I have to ask, how many of those Dr. Ho home therapy units do you own?

Since this is the third time this infomercial has been posted, it makes you wonder, are these guys stupid or is this some kind of willful campaign? Northrup is no better than Dr. Ho. He uses sensational statements that are clever manipulations of various bits of information to make a case. ISO is about film sensitivity. The intensity of light it takes to expose an image on a light sensitive material. The amount of light captured has nothing to do with it, nor should it. ISO is not a standard of noise, noise has it's own formula.

The only thing relevant about noise is, you need to determine what the highest amount of noise your work flow will tolerate is, and shoot at less than that. For APS-c for me I top out at 400 for comfort, 800 in a stretch, 1600 under duress. The differences are so small between 100 and 400, it doesn't matter that FF is better. The one stop difference between 100 and 350 is minuscule and you can see that in the IR swatches. Mr. Serous with his dead pan tone would have you believe what he's talking about is a big deal. It's not. You get useful images on MF at higher ISOs than you do on 4/3. APS-c and FF are just stops along the way, and if ISO 100-400 works for you, going to an FF for noise reduction is a waste of money.


Last edited by normhead; 10-09-2014 at 07:23 AM.
10-09-2014, 07:02 AM - 1 Like   #24
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This is a screen shot from Northrups video discussing the relative difference between the formats in respect of light gathering capacity.
Attached Images
 
10-09-2014, 07:02 AM - 1 Like   #25
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QuoteOriginally posted by marcusBMG Quote
No it doesn't. This is the deeper point.
How can a smaller sensor catch the same amount of light as a larger sensor. it can't and it doesn't.
I just went and took two pics at 200ASA with my 50mm f1.4 at f1.4 on my lumix g1 (2x crop factor) and my K-r, same shutter speed. pics came out the same. But the cameras are cheating. They are both set up internally to match the familiar ASA scale of brightness. In fact the G1 is producing a matching image off the smaller number of photons that are hitting the smaller sensor, in effect it is using a more sensitive ie a "faster" setting.

This is explained clearly by Northrup in this video: see from around 8 minutes on

Crop Factor with ISO & Aperture: How Sony, Olympus, Panasonic, Canon, Nikon & Fuji Cheat You - YouTube
Haven't had time to watch the video yet (at work now), but what I get from your post is that the ISO of crop cameras generally reported lower than it actually is, in order to produce a brighter image? Even if this is true, in practical means it just means the APSC sensor has a work harder to match the FF sensor. That actually makes the comparison easier, rather than if they were honest with it. Imagine if your table is true, and ISO 100 in FF doesnt produce the same brightness as ISO 100 in APSC? Would be so chaotic trying to compare then. Unintended benefit

If 70-200/2.8, ISO 100 on FF and 50-135/2.8 ISO 100 on APSC = same shutter speed, then I'd say they have equal light gathering capability for practical purposes

Last edited by Andi Lo; 10-09-2014 at 07:10 AM.
10-09-2014, 07:07 AM   #26
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QuoteOriginally posted by Andi Lo Quote
Mounting a 28-75/2.8 on FF is like shooting an (nonexistent) 18-50/2 on APSC for DOF purposes only
Only if you change the subject distance to get the same coverage. Of course the DoF will change, because you have changed the subject distance, which amongst other factors determines the DoF.
10-09-2014, 07:08 AM   #27
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QuoteOriginally posted by Andi Lo Quote
Haven't had time to watch the video yet (at work now), but what I get from your post is that the ISO of crop cameras generally reported lower than it actually is, in order to produce a brighter image? Even if this is true, in practical means it just means the APSC sensor has a work a bit harder to match the FF sensor. That actually makes the comparison easier, rather than if they were honest with it Unintended benefit
They don't. He's comparing sensors from different brands and different manufacturers. If he was doing it correctly, he would have taken a Nikon D800 and a Nikon D7000 and put the same lens and shot to see the result.

Or even just take a Nikon D800 and put it into crop mode. I assure you, putting the sensor into crop mode will not change your shutter speed/aperture/ISO given a specific exposure.
10-09-2014, 07:08 AM - 1 Like   #28
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QuoteOriginally posted by normhead Quote
I've been thinking about this video. he does a little add for the manufacturers who support this nonsense Guess who i pushing this agenda? Nikon an Canon, probably the two biggest companies pushing full frame camera. Of course they want Full Frame to be the centre of the universe. Of course they don't want MF mentioned in the video. OF course they want to subvert the definitions of Aerture or ISO to fit their sales strategy. This man is a shameless shill and nothing more. Ever piece of good information he presents is polluted by his relentless Full Frame ideology.

After the trashing this video has received in other threads, the OP should be embarrassed he even posted it.

But since he didn't

Aperture is not defined by DoF. Read the wiki definition, I posted it in the last thread where this was posted. DoF is about DoF, and it's not measured in stops, it's measured in measures of linear units, anyone who wants to measure DoF in stops is trying to do a con job on you.

ISO is not about total light collected. The man in the video is simply lying. There was more difference in the amount of light collected by the "sensor" in dil days when there were 8x10 film cameras and milota minoxs that were completely tiny. ISO hasn't been made obsolete by digital. The total amount of light captured by the film was never part of ISO. Again read the wiki entry. SO once again the author claims a term is irrelevant, that is still completely irrelevant. The brainwashing continues with his diagram where FF is the biggest sense. What happened to MF? Oh, well that doesn't fit with the Full Frame superiority mindset so, it's conveniently left off.

This man is lying through his teeth. I just hope no one gets sucked in by this nonsense.

If you believe this stuff, I have to ask, how many of those Dr. Ho home therapy units do you own?
I would like to respond to what you are saying Normhead but you are not making any sense at all. if you want to enage with the discussion then dicuss the points raised. I don't know why you are calling Northrup a liar, I suspect you haven't seen the video or don't understand it.
10-09-2014, 07:11 AM   #29
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QuoteOriginally posted by marcusBMG Quote
No it doesn't. This is the deeper point.
How can a smaller sensor catch the same amount of light as a larger sensor. it can't and it doesn't.
I just went and took two pics at 200ASA with my 50mm f1.4 at f1.4 on my lumix g1 (2x crop factor) and my K-r, same shutter speed. pics came out the same. But the cameras are cheating. They are both set up internally to match the familiar ASA scale of brightness. In fact the G1 is producing a matching image off the smaller number of photons that are hitting the smaller sensor, in effect it is using a more sensitive ie a "faster" setting.
I don't say that full frame doesn't have an advantage -- it generally does. You can stop down on full frame and get the same depth of field and just push the iso one stop up and get the same noise/dynamic range (assuming similar sensor tech). But the only "benefit" to full frame is if you are willing to accept less depth of field than you can get with APS-C if you want/need an APS-C equivalent photo, then by definition, you will get the same noise/SNR/dynamic range as on your crop camera.
10-09-2014, 07:12 AM   #30
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QuoteOriginally posted by kh1234567890 Quote
Only if you change the subject distance to get the same coverage. Of course the DoF will change, because you have changed the subject distance, which amongst other factors determines the DoF.
I tested this myself, shooting 75mm/2.8 on FF yields a virtually identical image (DOF wise) to 50/2 on APSC. I'd assume the rest of the focal range is the same as well. Had both cameras side by side and I didnt change my distance (its a half body portrait). I dont think I bothered to make the ISO / shutterspeed the same, was only concerned with DOF when I did the tryout. I can post the images later if you want

QuoteQuote:
he would have taken a Nikon D800 and a Nikon D7000 and put the same lens and shot to see the result.
I can do it with D600/D7000, I'm pretty sure the exposure values between the two will be the same though... I use both cameras side by side alot so I'm pretty sure I'd notice if they report different exposure values

QuoteOriginally posted by Rondec Quote
But the only "benefit" to full frame is if you are willing to accept less depth of field than you can get with APS-C if you want/need an APS-C equivalent photo, then by definition, you will get the same noise/SNR/dynamic range as on your crop camera.
Some photographers (me included) thinks less DOF is a real benefit (I can use a zoom on FF to do the job of a prime on APSC!) although I understand it's not for everyone

Last edited by Andi Lo; 10-09-2014 at 07:30 AM.
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