P-45 Digital back

I tried to post this question in medium format forum, but I didn't get any

substantial answer. Since P-45 Phase One digital back is used both on medium

and large format cameras, and from my previous experience, I got really good

answers on this forum.

 

Here is the question.

 

new P-45 digital back is 39 mp RAW format back, generating 117 Mb TIFF file.

Nice and dandy, but does lens resolution supports the resolution of this back?

I didn't find tech specs for Schneider lenses I use, but, for example Mamiya

and Zeiss 6x4.5 lenses ( which covers that sensor fully) have at the center

resolution of 70 lines /mm, or 1778 lines/inch. In the corners, that

resolution is around 40-45 lines/mm. For P-45 to generate 117 Mb file,

resolution of this sensor is 7216x5412 pixels, which is 147 pixels/mm or 3734

pixels/inch, which, in my opinion, surpases resolution of the lenses.

 

So my question is, is there a benefit of having 39 mp back and can that

surpass 117 Mb drum scan of 4x5 chrome, Velvia 50 for example, which has

resolution of 125 lines/mm or 3175 lines/inch. Total resolution of 4x5 chromes

would be in that equation 12,700 x 15,875 lines.

 

I'm not sure what is eact ratio of lines/mm vs piexels/mm, but, I think,

numbers speak for itself either way you turn it around.

Many lenses designed for 4 x 5 cameras are capable of delivering performance comparable to medium format lenses. Also, since you are using a smaller format, you need not worry about fall off toward the periphery since you are not likely to be using that part of the lens field. Also, there are new lenses specifically designed for digital sensors which should do very well. Look for example at the Schneider Digitar series.

 

On the other hand, if you are going to use a smaller format, it would be better to use a camera designed for that format. For a smaller format, you need to use shorter focal length lenses for the same angle of view. Thus you will end up using a wide angle 4 x 5 lens as a normal lens for your setup and extremely short focal length lenses for wide angle lenses. The minimum bellows extension on a 4 x 5 camera may limit how short you can go. If you plan to do view camera photography with such a digital back, you should make sure your camera can handle it. There are of course medium format view cameras, but they are pretty expensive.

Hi Leonard,.. thank you for your help trying to answer my question, I'm sorry, but I know all that. You are missing the point of my question.

You have to understand that lens resolution is in line pairs, so 70 lines/mm would translate to 140 pixels/mm.

 

Schneider rates their LF lenses between 90-200 lp/mm which is 180-400 pixels/mm which would exceed (but not by much) the 150 p/mm of the P39.

 

Of course, if you look at film, T-Max 100 can resolve up to 200 lp/mm which is almost three times as much as the P39. (Even TMZ can resolve 125 lp/mm).

Thank you Remi,

 

that does answer my question, P-39 or P-45 still does not get close to what film can do, and it is still questionable if lenses can support that sensor

I think I'd want to see some apples to apples test results before jumping to any conclusions

based on the numbers.

 

If you are looking to absolutely outperform 4x5 film I'd look at a http://wwwbetterlight.com

scanning back. You'll get a significantly larger dynamic range too --about 15 stops -- and

more accurate color as well.

 

Hoiw big are you planning to print and at what resolution will you be printing ?

Here is a comparison article on P45 vs 4x5 which may help

http://www.luminous-landscape.com/essays/Cramer.shtml

Mario,

 

I think you are missing the point. Most landscape photographers would not buy a P45 because of the cost, and low volume use. If however you're a commercial guy doing lot of work, it pays for itself in one year for some photographers. You save on film/lab costs, man hours doing processing, or driving around to get the films done,instant results to confirm, ready for image to be sent to a art director, etc. Unless you need really big prints, film will still outperform. Your key question should be will it save me more money using the P45 or will 4x5 film suffice for the few jobs you have that need it. The issue is can your business afford the initial purchase (unless it is leased) of a P45, will it pay for itself fast (technology ages quickly), and I would worry less about minor differences in quality. They both are extremely good. It is like worrying is 4x5 or 5x7 better for quality when they both are very high end and better then 35mm. Minor quality differences shouldn't matter, what is important is will it save you money,time, get the job to the customer on time, and protect your business from high capital costs that put a financial burden on smaller businesses and force you to charge higher prices then you competitor. Analyze what benefits you will get, do you really need it, rather then minor differences in performance.

"Here is a comparison article on P45 vs 4x5 which may help http://www.luminous-landscape.com/essays/Cramer.shtml"

 

Look like 4x5 film won by large margin. I guess phaseone needs to build 39*2*2 = 156MP to match 4x5 film, and it will cost you a house. Long live film....

Seriously, shoot films, it's cheap, and you can buy the house with the change.

Sorry for not answering the question. Let me try again. I may not be successful, but it may be helpful anyway.

 

In making these comparisons, you have to first understand what the figures mean. 147 piexels per mm is the sampling frequency. According to digital sampling theory, the maximal obtainable resolution, in the usual sense is half that or about 73 lp/mm. (As was already noted, each line pair needs at least two pixels.) But in actuality, you are not going to achieve the theoretical maximum. How close you get depends on the quality of the sensor array.

 

Let's suppose you do get very close to say 70 lp/mm. When you combine two elements of an optical system, the resolution you get is going to be less than the resolution of either. To get an accurate result, you need to multiply at the MTFs of the components. (The MTF gives the response as a function of frequency.) that is involved and it is not usually done. But there are various rules of thumb to estimate the result. One way is to take the square root of the reciprocal of the sum of the squares of the reciprocals of the components. Using that rule, combining two systems with a resolution of 70 lp/mm would result in a resolution of about 50 lp/mm.

 

Ideally, if you want to get the most out of a lens which can resolve 70 lp/mm, you should choose a medium which can itself deliver much more than that. You still won't get 70 lp/mm from the combination, but you may get close.

 

Note that you aren't really any better off doing it with film. Modern films that you would be likely to use are probably not going to deliver even 70 lp/mm. If, in addition, you scan, you add one more step, and that reduces the resolution even more.

 

On the other hand, when comparing 4 x 5, i.e. about 95 x 120 mm, to a 49.1 x 36.8 sensor array, you have to keep in mind the almost 2 to 1 advantage the former has in the size of the image. It has to be enlarged less, so you can get away with lower resolution. If you use film and scan with a very high quality scanner, you are likely to do better than the Phase One back can deliver. That is considering only resoltion. It should also be kept in mind that digital backs don't collect separate R,G, and B values for each pixel as a scanner would. Each pixel is a single color, and the result is processed via the Bayer algorithm to produce an RGB image. That may not affect resolution, but it could affect the quality of a color image.

 

Is any of that relevant?

Dear Elis, thank you, but their web site is down,. David, that is great article, but I see what I have stated before, greens on digital are funky, as well blues, I don't pay attention to color chart, also, I understand that things weren't calibrated in this test. ,.

 

Dear Van, ,.on my last assigment, I spent 600+ rolls of 220 chrome film, and about 12 boxes of 4x5 ( 50 sheets) so there is no question of money ( clients pay for that ) question is the quality,. and bigger question is hassle of doing such a big job overseas, where there are no labs, no chance to restock and probability of film being ruined in X-Rays,

 

I use a lot 6x12, 6x17 and 6x24 Panoramic cameras, so digital backs, are not that great on wide angle, except 35 mm on 6x4.5,.. but the question still is, does 39 mb, is any better than 30 or 22 mb because of lens resolution?

Hi Leonard,.. Thank you, that really got lots of things answered, I'm appoligize if I was rude in my first answer to your post, I understand quite a bit what is going on in film/digital enviroment, but it is hard to make a decision to go digital, when you are master of film,. traveling makes really good PR for digital,..I'm questioning all those numbers being thrown at us,. ( and $$ figures), how much of that is real and beneficial, and how much is just marketing, bigger numbers don't impress me, quality does,. and that is root of my question on this forum

Hey Mario,

The Phase One reps are really glad to bring a back out to someone to test if you are really

interested in buying on. You could do some of your own tests on your own subjects and

decide for your self. The new plus backs are also supposed to allow for long time exposures

and better higher iso performance. I don't know where you are located Global Imaging in

Denver has reps through out the west.

Mike Collett at Betterlight has put together a great explanation of the difference between film resolution in lp/mm, and resolution limits due to film grain size. Turns out that while a rating of 125 lines/mm is technically correct for film, it is not really usable for decent photography. At that level of detail, the grain size overwhelms the image being captured. This is a hard to understand without the sample images Mike put together. I am sure he would make them available to those who really want to know.

 

regards,

Yatish

Mario,

 

I think the bottom line is that the P45 comes close (but doesn't quite match) the resolution of drum-scanned 4x5, and the few landscapers who do use it accept a slight resolution loss in exchange for the convenience of medium format. With regards to lens resolution, my understanding is that the Rodenstock HR series is the only digital view camera lens line which consistently provides sufficient resolution for 39 MP sensors (as well as next-generation 50-60MP sensors), albeit at a cost of reduced image circle. As for medium format lenses from Hasselblad, Mamiya, etc., my understanding is that some lenses may require redesign (particularly wide angle) to fully resolve high-end sensors. Hasselblad just introduced a high-resolution 28mm, and Mamiya will reportedly ship a 28mm next year IIRC.

 

Personally, I'm waiting for the next generation of MF digital sensors before I consider whether to go MF digital. The industry is in such a state of flux right now (the new Hy6 camera platform, new lenses for most of the various camera platforms, the continuing software maturation process, etc.) that I'd prefer to let the smoke clear before making any decisions. I just can't get excited about paying $50K for a 39MP camera system which can't outresolve my current LF equipment right now.

My error as I mis-typed the betterLight URL.

 

Try: http://www.betterlight.com

The Phase One P45 is quite awesome, both in terms of its resolution, and its price! As a

landscape photographer, I see compelling advantages in using a $100 4x5 Fuji quickload

holder, a $60 box of Fuji film, and drum scanning (at 2400 to 4800ppi - $80-$100 -

depending on the image) to obtain digital masters of my top select images that I am

actually going to make prints from.

 

It is a simple fact that a photographer working in the field is going to drop the camera

back, either on the ground, in a creek, or to the botton of the ocean. This autumn, I

dropped a pack of Velvia quickload film in a creek, dried it out, and it worked great. If I

had dropped the film and my quickload back into the bottom of a lake, I would have been

out only $160, and I have extra boxes of film and an easily affordable backup back. There

is no way that I am going to buy two $30,000 (much less $15,000) backs given the fact

that film beats it from my point of view on a variety of levels.

 

What are those levels? For one thing, lens selection and cost. I don't need to use

specialized and expensive lenses optimized for digital and unusable on 4x5 film, while I

can choose from several decades of excellent quality large format optics. Also, using a

larger film area makes for more forgiving focal plane alignment. Then there's the

practicality of operating costs (including buy-in cost and inevitable replacement cost). If

you're a typical large format landscape photographer, rather than a commercial

photographer shooting high volumes, expensive digital backs aren't going to save money.

As for resolution, the fact is that a properly executed film image and drumscan still beat

the P45. I also like the fact that with an original transparency, I have a fixed image to refer

to in order to keep me honest in doing the Photoshop work that results in my fine print

master files. It is much more difficult to stay true to the original situation when working

from a RAW file. It's much more like printing from a negative, relying on one's memory for

what the scene looked like. We all know that our memories can be overly optimistic.

 

The bottom line from my point of view, is that in practical terms, for landscape

photographers or other relatively low volume large format photographers, film still

delivers superlative results at relatively low cost, and offers the most practical solution.

That said, commercial shooters working day-in, day-out, and particularly those working

with a client's art director on site, should consider a P45, no question.

That chip is pretty high rez,like higher than some of the dslr chips.

 

More specifically around 73 lp/mm if every row of pixels represents a line.

 

Kodaks old formula for film is the lens should be 3x the film rez to fully resolve the film.

 

Digital is less demanding on rez but is more demanding in that it requires a more telecentric lens design than film.

 

A foveon type sensor maxes out with a lens that is around 1.7x but the sd10 is a 54lp/mm camera, so in that case it takes a 90lp/mm lens to fully resolve that particular caemra.

 

Bayer digital seems to take more, like maybe 1.8x-2.2x depending on the chip aa filter etc.

 

All of that above came from actual rez tests from me a couple of years back.

 

So in the case of the p45 chip at 73lp/mm its going to take a really good lens to fully resolve it. If it fully resolves at 1.8x you would need a lens that resolved 130lp/mm.

 

In that case diffraction also will start to limit resolution. The diffraction limit at F8 is around 94 lp/mm so even at F8 you will be a bit compromised.

 

If it were me, I think I would either set up a rollei with PQ lenses (if still supported),hassy or a contax or if you are headed towards large format use digitar lenses that are designed for digital.

 

That said sopposedly the digitar lenses past F8 or F11 are like most other modern LF lenses except they are telecentric.

Dear Troy,. thank you very much for your detailed answer, that does support my thinking that just throwing numbers and megapixels ( and attaching price accordingly) is not neccessary getting that much more than what lenses can deliver. Also, I thank all other people that gave me much better insight what is happening with digital backs vs traditional film, not mentioning colors etc,,. mainly focusing on resolution.

And...

 

To me the p45 would be a superb studio setup, but I am not sure I would want to drag a 40g camera setup around in the field.

 

The p45 sensor rez is 7216x5412. I have a drum scanner and E100G scanned at 2000 dpi is a dead ringer for digital. At 2000 dpi a 4x5 scan returns 7600x9600 and also has a 1-2 pixel edge and is very clean.

 

The p45 file might have slightly better edge sharpness and would interpolate up good to a certain point but past that and all digital gets that plastic look. IMO a 3000 dpi 4x5 drum scan would look better than a p45 file interpolated up 200%.

 

The comparisons I have seen are close, ie the p45 is very close to 4x5 film, but if you look really close the p45 file is missing some of the tiny fine detail. Of course its also missing the grain, good or bad.

 

All that said you can print the p45 on a lightjet at 204dpi at around 24x36. You can print an uninterpolated 2000 dpi drum scan at almost 40x50.

troy, i am regularly printing 50x40 inch TIFF files processed from P45 RAW files at above

200 dpi. it's all in how you process your RAW file. i have had extraordinary results from

iridient's raw developer, which beats capture one hands down at high-end raw processing.

(raw developer though has a very hokey interface compared with capture one and i

wouldn't recommend it for dealing with great numbers of images at once).

 

is there any difference in a 2000 dpi print and a 200 dpi print? not really. there is,

however, a difference between digital and film when it comes to grain. as you say yourself,

digital is grainless. that means that you can manipulate and sharpen a digital file far more

than you can touch a scan from film. and the bigger you process the file, and the harder

you sharpen a digital image, the more noise you'll begin to see in the details. with a little

care, extreme scaling and manipulation with a P45 image file results in grain that only

begins to approach film grain.

 

mario's original question is very technical. from what i've seen, i would say that a digitar

schneider lens at f11 is sharper than a traditional lens. however, i'll leave it to others to

convert the physics to numbers.

 

i would ask you to consider the way in which you judge image quality. is sharpness and

resolving power really what you're looking for? i am committed to my P45, and i use it in

the field as a landscape photographer, as well as in the studio, for commercial work.

however, there's something that lens resolving power etc cannot really take account of,

and that is how a larger image circle seems to treat space. there's something specifically

medium format about the P45 even though it surpasses 4x5 in quality. i'm not sure how to

express this in words, but it won't be long before it's not necessary. i realise that i can no

longer really get pictures with the same spatial sense as 4x5 unless i stitch using a sliding

back adaptor on a studio camera (which is a devil on location, though i have done in the

most insane environments). so, unless scanning backs ever come into vogue, we will begin

to forget the spatial qualities of larger format imagery, just as we will forget what film

grain looks like, and we will forget that inkjet looks unfamiliar, and lightjet/lambda (which

is adapted to look similar to traditional C-type) will begin to look archaic. technology is

not linear.