Some crop factor maths

LuzArt · Jun 10, 2008

1.5x crop

31=46.5
43=64.5
77=115.5
21=31.5
35=52.5
40=60
50=75
70=105
85=127.5
16=24
45=67.5
10=15
17=25.5
100=150
135=202.5
60=90
250=375
200=300
300=450

1.2x crop

31=37.2
43=51.6
77=92.4
21=25.2
35=42
40=48
50=60
70=84
85=102
16=19.2
45=54
10=12
17=20.4
100=120
135=162
60=72
250=300
200=240
300=360

Interesting how some Pentax lenses would change their use. The FA43 Limited becomes much like it was on film, pretty darn close to a 'normal' view lens, while the FA31 Limited goes that much wider.

The FA77 Limited would be less tele, i wonder how much the appearance of it's bokeh would change?

The DA*35 Macro would be even more intriguing.

The DA16-45 would be handily wider, yet shorter at the long end when some feel it's already too short. So a DA17-70 would be an even better buy than it is soon to be.

The tele's are where it all get interesting/annoying/difficult. A 300mm focal length becomes even more necessary for everyday tele uses. Similarly tele macros like the DFA100 lose a considerable amount of reach.

We all just wonder don't we?

Ben

--

http://www.luzartphotography.com
http://luzart.blogspot.com

diomedian · Jun 10, 2008

Why are you providing 1.2x crop factors? Are there rumors of a 1.2x crop body?

Also, I don't think you could use the DA lenses on a 1.2x crop body without having the corners chopped off.

Jeremy

JensR · Jun 10, 2008

Hi Jeremy!

diomedian said:
Why are you providing 1.2x crop factors? Are there rumors of a 1.2x
crop body?

The argument goes like this:
FF is expensive
Pentax's trademark is in-body-SR
in-body-SR is expensive for FF
people want a larger capture area than APS-C
=> intermediate size gets chosen and Pentax might manage to provide SR with it.
Is this just a dodgy compromise? Or the best of both worlds?
We will see - or not.

diomedian said:
Also, I don't think you could use the DA lenses on a 1.2x crop body
without having the corners chopped off.

Depends on the lens and for zooms their zoom setting.
My 12-24 works from 16-24 on 24x36, for example.

Cheers
Jens

--

'Well, 'Zooming with your feet' is usually a stupid thing as zoom rings are designed for hands.' (Me, 2006)
My Homepage: http://www.JensRoesner.de

richardplondon · Jun 10, 2008

diomedian said:
Why are you providing 1.2x crop factors? Are there rumors of a 1.2x
crop body?

In the land of wishful rumour, all things are possible...

diomedian said:
Also, I don't think you could use the DA lenses on a 1.2x crop body
without having the corners chopped off.

I remember tests here of a 40mm DA lens on (1x) 35mm film, without any visible problem. Perhaps shorter lenses than that may still be OK. Longer lenses are optically no problem, AFAIK.

1.2x should work perfectly fine, except with the widest DA lenses.

RP

JimmyTheHand · Jun 10, 2008

Why would the bokeh change with crop? it might change a bit because of different sampling resolution and I suppose could look different on edge of photos compared to centre

LuzArt said:
The FA77 Limited would be less tele, i wonder how much the appearance
of it's bokeh would change?

--
J.

LuzArt · Jun 10, 2008

Think you answered you're own question there!

I don't actually know what would happen to bokeh, i'm just curious if anything would change.

Ben
--

http://www.luzartphotography.com
http://luzart.blogspot.com

bdery · Jun 10, 2008

LuzArt said:
The FA77 Limited would be less tele, i wonder how much the appearance
of it's bokeh would change?

It wouldn't.

The lens properties do not change because of the crop factor.

The crop factor means that the sensor uses the center of the lens and not the extreme borders, nothing more. It's exactly the same as if you manually cropped a larger image.

--
bdery

Québec city, Canada

Pentaxian in the making
http://s108.photobucket.com/albums/n13/bdery/

Lance B · Jun 10, 2008

A 1.1 or 1.15 or 1.2 crop would suit me.

1.1 x

31=34.1
43=47.3
77=84.7
21=23.1
28=30.8
35=38.5
40=44
50=55
70=77
85=93.5
16=17.6
45=49.5
10=11
17=18.7
100=110
135=148.5
60=66
250=275
200=220
300=330

1.15 x is my preference.

31=35.7
43=49.5
77=88.6
21=24.2
28=32.2
35=40.3
40=46
50=57.5
70=80.5
85=97.8
16=18.4
45=51.8
10=11.5
17=19.6
100=115
135=155.3
60=69
250=288
200=230
300=345
--
Lance B
http://www.pbase.com/lance_b

robin0112358 · Jun 10, 2008

Unless there is a camera announced with a totally new sensor size I am not understanding this thread.

Why not just put your FA31 on a film body and get 1x crop?

SturmMD · Jun 10, 2008

If you're going to give answers with 3 decimal places, why not use the more correct 1.53x crop factor

.
Then again, the lens actual focal lengths are probably not exact as well.

--
'Sleeping too much makes you tired.' - Me

cycoj · Jun 10, 2008

I really don't understand the obsession people have with a FF sensor. They are expansive, and I don't think they are worth the price difference.

Their main advantage is better noise performance for the same resolution, however I believe that we haven't reached the end of the line yet with respect to noise behavior of DSLR sensors, and the money spent on developing a FF sensor is better spent on researching how to reduce sensor noise in general.

Assuming a 1.2 crop factor sensor, the difference in area between such a sensor and a APS-C sensor is about the same as between APS-C and 4/3rd. I don't think the differences in noise performance between Olympus and Pentax are really that big. Especially if Pentax would cost twice as much as Olympus (which would be a cheap FF camera), people would by Pentax if the price difference was that big.

You also need to take into account that because of the shallower depth of field camera shake becomes a bigger problem, so you again loose some of the advantages of less noise provided by the larger sensor.

The other thing to consider is, that it's generally more difficult thus more expansive to build the same quality lens for FF than for 1.5 crop.

My opinion is if you really want maximum quality and noise performance, go MF. That is a significant difference in sensor size.

FF is a marketing hype IMO

Jochen

LuzArt · Jun 10, 2008

--

http://www.luzartphotography.com
http://luzart.blogspot.com

LuzArt · Jun 10, 2008

Quite possibly Lance!

Ben
--

http://www.luzartphotography.com
http://luzart.blogspot.com

LuzArt · Jun 10, 2008

cycoj said:
I really don't understand the obsession people have with a FF sensor.
They are expansive, and I don't think they are worth the price
difference.

I guess you're not in the market that Pentax might be going for with a FF camera.

cycoj said:
Their main advantage is better noise performance for the same
resolution, however I believe that we haven't reached the end of the
line yet with respect to noise behavior of DSLR sensors, and the
money spent on developing a FF sensor is better spent on researching
how to reduce sensor noise in general.

We actually don't really know what Pensung are up to, do we??

cycoj said:
Assuming a 1.2 crop factor sensor, the difference in area between
such a sensor and a APS-C sensor is about the same as between APS-C
and 4/3rd. I don't think the differences in noise performance between
Olympus and Pentax are really that big. Especially if Pentax would
cost twice as much as Olympus (which would be a cheap FF camera),
people would by Pentax if the price difference was that big.

There's a whole lotta people out there who would love FF.

cycoj said:
You also need to take into account that because of the shallower
depth of field camera shake becomes a bigger problem, so you again
loose some of the advantages of less noise provided by the larger
sensor.

The other thing to consider is, that it's generally more difficult
thus more expansive to build the same quality lens for FF than for
1.5 crop.

But you see, many DA lenses won't be a problem in terms of vignetting on a FF sensor. Many show no signs of vignetting on film and since there is very little chance of an FF sensor being a 1.0x crop, they shouldn't cause issues on a 1.2x crop.

cycoj said:
My opinion is if you really want maximum quality and noise
performance, go MF. That is a significant difference in sensor size.

Again, who knows eh? The future is long, nothing is written in stone yet.

cycoj said:
FF is a marketing hype IMO

No it isn't, it's just not popular yet. There's many a market to be a part of and many a market yet to be created. Watch this space.

Ben
--

http://www.luzartphotography.com
http://luzart.blogspot.com

JensR · Jun 10, 2008

Hi Jochen!

cycoj said:
I really don't understand the obsession people have with a FF sensor.

It's not an obsession =)

Grab a 43/1.9, an MZ-5n and some film or rent a 5D and you'll understand. Or not.

cycoj said:
They are expansive, and I don't think they are worth the price
difference.

Fair enough. Other people don't need all the fancy "features" of APS-C cameras }:->

cycoj said:
Their main advantage is better noise performance for the same
resolution,

plus better viewfinder and better DOF control and being less dependent on high lens resolution plus wider views available.

cycoj said:
however I believe that we haven't reached the end of the
line yet with respect to noise behavior of DSLR sensors, and the
money spent on developing a FF sensor is better spent on researching
how to reduce sensor noise in general.

This isn't an either/or story. When APS-C sensors get better, FF sensors get better. If FF sensors get better, APS-C sensors get better. Most of the technology used for this one can be used on that one.

cycoj said:
Assuming a 1.2 crop factor sensor, the difference in area between
such a sensor and a APS-C sensor is about the same as between APS-C
and 4/3rd. I don't think the differences in noise performance between
Olympus and Pentax are really that big.

Well. I'm quite sure many here dislike Olympus for the noise reason. But I also think that 1.2 is not fish not flesh and 1.0 makes more sense.

cycoj said:
You also need to take into account that because of the shallower
depth of field camera shake becomes a bigger problem,

? Camera shake and DOF have no relation. You can't prevent camera shake or its showing by stopping down.

cycoj said:
The other thing to consider is, that it's generally more difficult
thus more expansive to build the same quality lens for FF than for
1.5 crop.

No, it is cheaper for FF. You should compare equivalent lenses, which means same angle of view and same depth of field. You will notice that generally FF lenses are cheaper than APS-C lenses, if there are equivalent lenses. Often there is no equivalence, because the FF lenses are "too fast" compared to the APS-C ones.

cycoj said:
My opinion is if you really want maximum quality and noise
performance, go MF. That is a significant difference in sensor size.

Compared to "FF", MF has huge bodies, limited lens selection, slow operation speed, comparatively bad high ISO performance.
It's specialised.
The jump from APS-C to dMF is way too big to drop "FF".

cycoj said:
FF is a marketing hype IMO

Which FF cameras do you have experience with?

Cheers
Jens

--

'Well, 'Zooming with your feet' is usually a stupid thing as zoom rings are designed for hands.' (Me, 2006)
My Homepage: http://www.JensRoesner.de

cycoj · Jun 10, 2008

LuzArt said:
cycoj said:

I really don't understand the obsession people have with a FF sensor.
They are expansive, and I don't think they are worth the price
difference.

Click to expand...

I guess you're not in the market that Pentax might be going for
with a FF camera.

LuzArt said:

Their main advantage is better noise performance for the same
resolution, however I believe that we haven't reached the end of the
line yet with respect to noise behavior of DSLR sensors, and the
money spent on developing a FF sensor is better spent on researching
how to reduce sensor noise in general.

Click to expand...

We actually don't really know what Pensung are up to, do we??

LuzArt said:

Assuming a 1.2 crop factor sensor, the difference in area between
such a sensor and a APS-C sensor is about the same as between APS-C
and 4/3rd. I don't think the differences in noise performance between
Olympus and Pentax are really that big. Especially if Pentax would
cost twice as much as Olympus (which would be a cheap FF camera),
people would by Pentax if the price difference was that big.

Click to expand...

There's a whole lotta people out there who would love FF.

Is there? Even if the camera costs $3000+. I think the "lotta people" gets a "lotta less" people at that price.

LuzArt said:
LuzArt said:

You also need to take into account that because of the shallower
depth of field camera shake becomes a bigger problem, so you again
loose some of the advantages of less noise provided by the larger
sensor.

The other thing to consider is, that it's generally more difficult
thus more expansive to build the same quality lens for FF than for
1.5 crop.

Click to expand...

But you see, many DA lenses won't be a problem in terms of vignetting
on a FF sensor. Many show no signs of vignetting on film and since
there is very little chance of an FF sensor being a 1.0x crop, they
shouldn't cause issues on a 1.2x crop.

But it's not only vignetting, all lens aberations will be stronger in the corners. That's the reason why you usually have less corner sharpness than centre sharpness. Sure it's possible to control this, but it's more difficult, thus more expansive.

LuzArt said:
LuzArt said:

My opinion is if you really want maximum quality and noise
performance, go MF. That is a significant difference in sensor size.

Click to expand...

Again, who knows eh? The future is long, nothing is written in stone
yet.

LuzArt said:

FF is a marketing hype IMO

Click to expand...

No it isn't, it's just not popular yet. There's many a market to be
a part of and many a market yet to be created. Watch this space.

I say yes. The thing is not many people are buying FF cameras, they are way too expansive. However people buy into the system because the maker has a FF camera. I don't understand the reasoning, but people think C/N are more serious makers because they have a FF camera. I'd call this marketing.

I would argue the actual market is marginally small. I don't think the Canon and Nikon FF cameras are sold by the bucket load. The 5D is just becoming more popular now because it's getting relatively cheap. And from what I've seen I don't find the IQ of the 5D that stellar. Not much if any better than the K20D or 450d.

Note I'm not criticising Canon, it's an almost 3 year old camera, what I'm saying is, that the price of the 5D is now coming into price ranges where people start buying it, but it actually does not perform much better than current APS-C cameras because technology has moved on.

Jochen

cycoj · Jun 10, 2008

Jens I actually started a detailed reply to you, however you have a lot more photography knowledge than I have so I just get myself into trouble

.

I agree that FF sensors have some desirable advantages. However my main point is most people here and otherwise would not be willing to pay the price, both in money and disadvantages. That's why the FF sensor cameras are an expansive niche, atm. And I think Pentax would be better off competing on other grounds.

Cheers
Jochen

Kanguru · Jun 10, 2008

Lance B said:
A 1.1 or 1.15 or 1.2 crop would suit me.

Thanks Lance & Ben. I've been wishing for 1.2 crop, 1.15 is even better.

It's 2/3rds of the way from 1.5x to FF for half the extent of problems manufacturing FF sensors.
Better yield => lower costs.

Extrapolate K20D sensor to 1.15x it's 24Mpix; that's quite plenty for a lot of us so it may be overkill to go all the way to FF.

RBroomall · Jun 10, 2008

There's a lot of market here...just because there are a couple of gorillas in the parlor dosen't mean Pentax couldn't give them a healthy run for their money... but is it the safe play?.

I had hoped that Pentax would have created a scanner back for the 645 and or 6x7 but they aren't looking at instruments of art rather instruments that will market easily.
That said, I would guess the FF is not the safe play for profitability.

--
Enjoying the new K20D

Lance B · Jun 10, 2008

rparmar said:
Unless there is a camera announced with a totally new sensor size I
am not understanding this thread.

This is part of the speculation.

Instead of a FF camera, Pentax might announce a 1.1x, or 1.15x, or 1.2x crop factor sensor due to the fact that SR may require room "around" the sensor for movement outside the image circle of the coverage of FF lenses. In other words, if Pentax do make a FF sensored camera, if SR is employed then SR may move the sensor outside of the image circle coverage of a FF lens.

robin0112358 said:
Why not just put your FA31 on a film body and get 1x crop?

--
Lance B
http://www.pbase.com/lance_b

Some crop factor maths

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