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08-27-2014, 01:28 PM   #151
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QuoteOriginally posted by Nicolas06 Quote
The 50-135 f/2.8 on APSC would be equivalent to an 75-202 f/4.5 in term of deph of field and framing.

As apparently the subject isolation was not said to be a big problem I didn't mention it (using "close" term).

On my side I own this 50-135. Honestly my feeling is the focal lens range is well suited for headshoots and portraiture in general of one person and not especially a full body shoot. Otherwise you need to be too far away. You would prefer a focal lens like 28-35mm on APSC and so 35-50 on FF...

But if you do an headshoot with this 50-135 using f/2.8 you really isolate your subject, in particular as the focal lens grows. It even begin to be a real problem, past 100mm, I'd rather stop down to f/4 or f/5.6 to have all the subject in focus... And still the background will be pleasantly blurred.

Wider apperture than f/2.8 for me are usefull but not that mandatory for long focal lenses, even on APSC. Of course everyone is free to have it's own opinion on this topic.
Regarding focal lengths past apsc 100mm (150mm FF eq.) I have to agree: I don't really see much use in an aperture faster than f2.8 (f4 FF eq.). The new mirrorless FF system shows that a 70-200 lens does not háve to be big and bulky, see the new Sony G FE 70-200 f4.
However, what I dó find lacking in the Pentax apsc lens offerings, is the apsc eq. of FF 28/2 and 35/2, where the subject isolation/blending at f2 (FF) is a sore miss when being limited to Pentax apsc.
Hence my belief that for apsc lenses like a 18/1.4 or 24/f1.4 are far more desireable than they are realistic for a Dslr apsc system like Pentax. Alas, only Fuji seems to be able to provide a true FF eq. apsc system.
Which leaves no other option for Ricoh to promote a compact Pentax FF Dslr, or see those like myself partly migrate to another system, which is very well as far as I am concerned, but is it what Pentax really wants?
Once switched, and investing in lenses and cameras of one of the other brands, it becomes less likely to return.
So let's not deny that the Pentax apsc system, good as it is, can not replace an FF system.

Chris


Last edited by Chris Mak; 08-27-2014 at 01:40 PM.
08-27-2014, 02:38 PM   #152
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QuoteOriginally posted by stevebrot Quote
Is this where the great cry of sensor equivalence is raised?
Apparently!!! The very next comment!

QuoteOriginally posted by ElJamoquio Quote
f/4.5 sensor quality (ISO 1000 on APS-C has the same performance as FF with ISO 2200)
As I said...It as so counter intuitive...

QuoteOriginally posted by jsherman999 Quote
It's only f/2.8 for exposure, not Total Light, so your f/2.8 is going to be noisier on aps-c (sensor dependent of course.)
?????? If you say so, Jay. Remember, I am one of those guys who is firmly in the "would really like a FF" camp.

This is where the discussion goes into stuff like "flux per pixel site" or something like that.

I personally believe that photographic film offers the highest potential return on a per photon basis. What could be more atomic than individual atoms?


Steve

(... is there a physicist in the room? The smoke is getting (predictably) thick in here...)
08-27-2014, 04:18 PM   #153
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QuoteOriginally posted by Chris Mak Quote
Hence my belief that for apsc lenses like a 18/1.4 or 24/f1.4 are far more desireable than they are realistic for a Dslr apsc system like Pentax. Alas, only Fuji seems to be able to provide a true FF eq. apsc system.
Which leaves no other option for Ricoh to promote a compact Pentax FF Dslr, or see those like myself partly migrate to another system, which is very well as far as I am concerned, but is it what Pentax really wants?
Once switched, and investing in lenses and cameras of one of the other brands, it becomes less likely to return.
So let's not deny that the Pentax apsc system, good as it is, can not replace an FF system.

Chris
I agree with you on this even through there are some 24mm f/1.4 is you are interrested. I think of the Samyang. Me, I'am not really interrested because even through this is quite interresting rendering I'am not sure it is usefull so often in practice... And this kind of lens is big. But you can buy it, no problem.
08-27-2014, 04:41 PM   #154
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QuoteOriginally posted by ElJamoquio Quote
f/4.5 sensor quality (ISO 1000 on APS-C has the same performance as FF with ISO 2200)
QuoteQuote:
As I said...It as so counter intuitive...
I should elaborate. As one of my more arcane practices, I shoot 4x5 large format. I own a Rodenstock 150mm f/5.6, which is considered a "normal" lens for that format. Are my images taken at f/5.6 with that lens magically transformed to be an equivalent to a FF (36x24mm) image taken with a 50mm f/2?*

Put another way, assuming that a 4x5 digital sensor with the same pixel density as used by the Sony A7s existed (~170 Megapickles), would the two lenses and systems be fully equivalent image-wise?

In less theoretical terms, say I scanned a fine-grained ISO 100 negative at 94 pixels/mm* to yield a 108 Megapickle image (12000 x 9000 pixel dimension). At 94 pixels/mm, digital noise on the scanner is negligible (linear array). Additionally, visible film grain at that resolution is similarly negligible. I know we are talking apples and oranges here since what I just described is a signal to noise ratio that is pretty high. Given that the A7s has an approximate linear pixel density of 119 pixel/mm would you consider the two systems to be equivalent with the Sony at ISO 100? If not, how many stops penalty are we going to assess the 50/2 in this comparison.

Is it possible that the notion of equivalence is not so well-defined outside the APS-C/FF debate and is based on a very narrow set of assumptions regarding sensor performance characteristics? Is it also possible that my 4x5 with the 150/5.6 offers little benefit over 24x36 FF other than capture resolution and dismally narrow DOF? Oh, I also forgot the cameras movements.


Steve

(...continues to wonder how the word "stop" came to be assigned to so many things photographic...the 4x5 is two stops larger format than FF?)

* Similar DOF and FOV (cropped on the short axis to 3:2 ratio). Absolute aperture size is the same for both lenses meaning that the same amount of light will pass through both lenses for a given amount of time. I might mention that the 150/5.6 has an image circle somewhat larger than the 4x5 frame cropped to 3:2 ratio.

** The real world max resolution for my scanner. I never scan that high for 4x5; the files are too big.


Last edited by stevebrot; 08-27-2014 at 05:04 PM.
08-27-2014, 05:34 PM   #155
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QuoteOriginally posted by Rondec Quote
I think a 55mm works pretty well on APS-C, as does the 77mm for portraits, but there is no doubt that full frame has an advantage when it comes to portraiture and subject isolation. It is not a miraculous thing -- particularly not in the 70 to 200mm range.

But the OP seemed to be talking about landscape photography, where I really don't see much of an advantage for full frame except when it comes to printing large.
Agreed, it's what I use today - either the 50mm 1.7 or 1.2, depending on how much of a rush I'm in (AF vs not), sometimes stopped down just a bit. I get results that are technically great, with the exception that it doesn't look like 85mm would in terms of facial distortion. I shoot the same subjects with the 70-200 in a slightly different way of course, so I see a difference. I really dig that Sigma 70-200!

For comparisons sake, here is a link that sums it up ( I think I've posted this before, but what the heck... )
http://www.stepheneastwood.com

The posing and framing with those two lenses/situations is quite different, and it's a practical impossibility for me to shoot the headshots I use the 50mm for @ 85mm (say with the 70-200) on APS-C, because I would need a ladder! Maybe with the 85mm on a FF I'd have to adjust a little bit, but at least within the realm of the possible. Let me explain...

I typically only have 5 or 10 minutes to shoot 8-10 portraits, often at the least opportune time & place during a wedding, so it's 'set exposure, pose subject, dial up focus, lay on the shutter while talking/directing'. Of the 10-20 shots per person, there is always a perfect shot. Since these are weddings there is no going back, and for consistency everyone has to be shot at the same time... so no ladder. These are shot from just above the subject; no double chins, shrinks away the body while still giving idea of how everyone was dressed, and it gives me great control of the background.

Is that too specific a use-case? Maybe. Probably for this discussion. But now that I have a crate of Pentax glass I'd rather they just gave me a dang FF, rather than try to unload most of it to pay for a CaNikon body. Or maybe a 645Z, but that's not ideal either.

Bringing this back to 'can you tell the difference?' - for landscapes, probably not. I'd rather shoot those big at f/64 anyway.

But do clients see a difference in their own image, or image of friends / family? I think so, even if subconsciously. But it may have more to do with things other than just DoF.

Last edited by noser; 08-27-2014 at 05:40 PM.
08-27-2014, 11:43 PM   #156
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QuoteOriginally posted by noser Quote
Agreed, it's what I use today - either the 50mm 1.7 or 1.2, depending on how much of a rush I'm in (AF vs not), sometimes stopped down just a bit. I get results that are technically great, with the exception that it doesn't look like 85mm would in terms of facial distortion. I shoot the same subjects with the 70-200 in a slightly different way of course, so I see a difference. I really dig that Sigma 70-200!

For comparisons sake, here is a link that sums it up ( I think I've posted this before, but what the heck... )
http://www.stepheneastwood.com

The posing and framing with those two lenses/situations is quite different, and it's a practical impossibility for me to shoot the headshots I use the 50mm for @ 85mm (say with the 70-200) on APS-C, because I would need a ladder! Maybe with the 85mm on a FF I'd have to adjust a little bit, but at least within the realm of the possible. Let me explain...

I typically only have 5 or 10 minutes to shoot 8-10 portraits, often at the least opportune time & place during a wedding, so it's 'set exposure, pose subject, dial up focus, lay on the shutter while talking/directing'. Of the 10-20 shots per person, there is always a perfect shot. Since these are weddings there is no going back, and for consistency everyone has to be shot at the same time... so no ladder. These are shot from just above the subject; no double chins, shrinks away the body while still giving idea of how everyone was dressed, and it gives me great control of the background.

Is that too specific a use-case? Maybe. Probably for this discussion. But now that I have a crate of Pentax glass I'd rather they just gave me a dang FF, rather than try to unload most of it to pay for a CaNikon body. Or maybe a 645Z, but that's not ideal either.

Bringing this back to 'can you tell the difference?' - for landscapes, probably not. I'd rather shoot those big at f/64 anyway.

But do clients see a difference in their own image, or image of friends / family? I think so, even if subconsciously. But it may have more to do with things other than just DoF.
If you think you need 85mm on APSC for the compressed rendering it provide, you'd need 127mm to get the same compressed rendering on FF. The 85mm shoot on FF would look like the 55mm shoot in term of perspectives. This mean that it would not change your problem a little bit.

I agree that you might have better in focus - out of focus transitions, more shaprness down to fine details and less deph of field, but none of theses is what you ask for.
08-28-2014, 10:25 AM   #157
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Also, FWIW, on digital f/64 would be a horrible, horrible choice. You'd be so far past the sweet spot on almost any lens you would probably have been better off shooting the scene wide open. Even f/16 is pushing things with a digital setup.
08-28-2014, 10:55 AM   #158
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QuoteOriginally posted by chaza01 Quote
Why are FF images so much more pleasing than APS-C
Cos we can't yet do 'em on a Pentax DSLR.

08-28-2014, 11:11 AM   #159
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QuoteOriginally posted by Sagitta Quote
Also, FWIW, on digital f/64 would be a horrible, horrible choice. You'd be so far past the sweet spot on almost any lens you would probably have been better off shooting the scene wide open. Even f/16 is pushing things with a digital setup.
Just to elaborate...

On APS-C, I often consider f/16 the 'limit', beyond which I only press if I can't focus stack, or use a tilt-shift, or don't have an ND filter.
For FF that's F/25 or so.
For 645D that's F/32
For 645 that's F/40
For 67 that's F/48
For 4x5 that's F/93!!!

Let's claim that digital stops at 645D - in which case f/64 is going to be pretty diffraction limited.
08-28-2014, 11:22 AM   #160
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QuoteOriginally posted by ElJamoquio Quote
Just to elaborate...

On APS-C, I often consider f/16 the 'limit', beyond which I only press if I can't focus stack, or use a tilt-shift, or don't have an ND filter.
For FF that's F/25 or so.
For 645D that's F/32
For 645 that's F/40
For 67 that's F/48
For 4x5 that's F/93!!!

Let's claim that digital stops at 645D - in which case f/64 is going to be pretty diffraction limited.
This is counting the same total number of pixels...

Diffraction begin to alter the image with the 16MP K-5 at f/11.. f/16 is already far worse and f/8 tend to be better except for very low end lenses and macros. For the K3 it is something like f/9 or f/10 then.

For an 16MP FF that's f/16. But for a 36MP FF that's obviously f/11 again.

For 16MP 645 that would be f/22. Now for an 51MP 645 sensor that between 3-4 time more pixels and so it will start to show at something like f/13.
08-28-2014, 12:43 PM   #161
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QuoteOriginally posted by Nicolas06 Quote
This is counting the same total number of pixels...
Kinda, but really, it's assuming the same final image display.

If you compare a 16MP at say 15x10" and a 36MP image at say 22.5"x15", and stand the same distance from both, you would observe equal diffraction 'softness' when they're both at F/16.
If you compare a 16MP at say 15x10" and a 36MP image at say 15"x10", and stand the same distance from both, they will be equally diffraction limited when the APS-C is at F/16 and the FF is at F/25.
08-28-2014, 03:09 PM   #162
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QuoteOriginally posted by ElJamoquio Quote
Kinda, but really, it's assuming the same final image display.

If you compare a 16MP at say 15x10" and a 36MP image at say 22.5"x15", and stand the same distance from both, you would observe equal diffraction 'softness' when they're both at F/16.
If you compare a 16MP at say 15x10" and a 36MP image at say 15"x10", and stand the same distance from both, they will be equally diffraction limited when the APS-C is at F/16 and the FF is at F/25.
I typically don't decide to print 1.5x time larger just because it is 36MP intead of 16MP or because it is an APSC or an FF. While theoretically sound I see no practical use for your comparisons. Reality is that if you expected to get some use of your pixelized sensor but didn't use a sensible apperture, you will get sub par results. Be it because you crop, because you print large or whatever.

I checked for the fun actual lenses performances (so not only diffraction) on some FF tests at photozone:

Already at f/11 on a 24MP FF (so not even this D810 that would be even more diffraction limited)
- Nikkor 35mm f/1.4 decrease it's MTF score by 15% at f/11 compared to f/4
- Nikkor 85mm f/1.4 decrease it's MTF score by 10% at f/11 compared to f/4
- Nikkor 70-200 f/2.8 zoom versionII, see a 20% decrease in MTF score by 20% at f/11 compared to f/4
- Nikkor 24mm f/1.4 also has a 15% decrease at f/11 compared to f/4

I saw similar figures on Zeiss lenses too. And all of the time the perf charts are limited to f/11.

But if I check for a macro lens where it is expected to stop down more and I look the Zeiss macro I still see a 18% decrease by f/11 a 25% decrease by f/16 and a 40% decrease by f/22.

The performance start to decrease in practice at f/11 for both FF and APSC. Actually the decrease in performance at f/22 is not as visible on the APSC sensor than on the MF sensor. At least on the Nikkor 85mm macro.

The more room to stop down with FF argument is just unfounded at least on modern highly pixelized sensors.
08-28-2014, 03:27 PM   #163
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QuoteOriginally posted by Nicolas06 Quote
The more room to stop down with FF argument is just unfounded at least on modern highly pixelized sensors.
It's completely 'founded'. It's based on the fact that the image won't be magnified as much, so the airy disk diameter can be larger before it impacts the image.

When you compare at a pixel level, you're enlarging the image on FF more than on APS-C. You're looking closer. That's why it doesn't matter in a practical sense.
08-28-2014, 04:14 PM   #164
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QuoteOriginally posted by ElJamoquio Quote
It's completely 'founded'. It's based on the fact that the image won't be magnified as much, so the airy disk diameter can be larger before it impacts the image.

When you compare at a pixel level, you're enlarging the image on FF more than on APS-C. You're looking closer. That's why it doesn't matter in a practical sense.

Nicolas is correct. Resolution is ultimately diffraction limited by aperture. For the same DoF, APS-C and FF will have the same theoretical max resolution. For example, APS-C at f/8 and FF at f/11 will both max out at 15Mp approximately. It means that the 36Mp D800 at f/11 will resolve no more detail than a 16Mp K5 at f/8.

You do not even have to pixel peep. You could just blow up the 16Mp image to 36Mp to achieve the same print size and detail as the original D800 shot. The D800 ultimately is just wasting space at f8 and smaller.
08-28-2014, 04:42 PM   #165
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QuoteOriginally posted by dtmateojr Quote
For the same DoF, APS-C and FF will have the same theoretical max resolution.
Yes, that is another way to state what I have said.



QuoteOriginally posted by dtmateojr Quote
It means that the 36Mp D800 at f/11 will resolve no more detail than a 16Mp K5 at f/8.
That's wrong though.
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