Sunday, January 22, 2012

Medium Format Vs. 24X36

As you know, I have been struggling with whether to go to the Pentax 645D. There is a controversial article by Mark Dubovoy on Luminous Landscape at the moment - to the effect that 'real photographers shoot medium format'. Of course, that isn't what Mark said, but it is what he implied - that no matter what the print size, one could see the difference between medium format and smaller formats.

The example he used showed distortion with the dslr image, and greater contrast and thus less well controlled highlights, and better shadows.

Of course, much of this is a function of the particular lens and f stop he chose to use, and I dare say the two images could have been made to look MUCH closer to each other with a bit of care.

My immediate reaction was 'what a load of bull', but then I calmed down and decided to look at far better comparisons made in some of the reviews of the Pentax 645D, in which images are compared to the  Canon 1Ds3.

I made prints of reasonable size, 24 inches in the long dimension - something that both cameras should be capable of making. I then looked at the images at 100%.

I have poured over the images, and here is what I have found. If one looks at the finest details, branches on the horizon miles away, there is nothing to separate the Pentax from the Canon at this size of print.  The same applies to railings and bricks and anywhere the contrast in tones is significant. Where I can see a difference between prints is in the low contrast areas, branches against bushes or downed leaves. Here there is a noticeable difference in the Pentax images - it's as if large areas (up to 1/4 inch of the print) were smeared, the colour blended, a complete absense of texture and detail and even simple variation in tone, on the Canon image. it isn't about greater resolution (which doesn't really show up until you make very large prints), but if the Canon can smear details over 1/4 inch at this size, it can still do that over 1/8 of an inch in a 12 inch print - that is definitely visible.

I don't know what the difference is - whether there is a lot more manipulation of data to squeeze every bit of accutance (edge sharpness) and low noise out of the Canon at base ISO, or whether this loss is the fuzzy filter, or due to the number of bits per pixel in the pipeline, or what - all I know is that for all I think Mark picked a poor example, he is fundamentally right that there is something different about medium format.

Whether this will still be true when there are 36 megapixel full frame dslrs without fuzzy filters remains to be seen.

It reminds me though of the days of film when people using Technical Pan and special compensating developers could show extremely sharp prints, albeit terrible ones, lacking in the tonalities that were readily visible in an 8 inch print when comparing 6X6 with 35 mm.

Careful examination of the two digital images at 200% clearly shows that no amount of sharpening or local contrast enhancement is going to bring back the missing texture in the smaller camera images - for whatever reason.

I wish I knew the reason. It would help me decide whether to fork out $10,000 for the Pentax, or spend almost 2/3 less for the next generation Canon or Nikon with 36 megapixels. Those cameras will have sensors 3 years newer than the Pentax, but their pixels will be considerably smaller than the Canon 1Ds3 has now - does this mean even more loss of subtle contrast detail?


Sandy Wilson said...

Real photographers use either 5x4 or 8x10. Or a 5x4 with a Phase One digital back or if you have the cash a Hasselblad with 80 million pixel back.

Deep down George I think what you would really like is to own a Hasselblad.

So would I, but it could only happen if the UK National lottery came up.

Anonymous said...

You'll have your answer with regard to the D800 in a matter of weeks so don't sweat it.

Royce Howland said...

Well, you know my bias. :) I have, shoot and like smaller formats for what they're great at. But all other things being equal, a larger digital format will trump a smaller digital format simply because the larger format is capturing more light at a given exposure. This will manifest in the shadows (better detail, less noise) and even to an extent in the darker half tones (better fine tonal variation). Such is the nature of linear digital sampling.

Of course, not everything else is equal. Probably at least some of what you're seeing here and in the examples of the next post is the 1Ds Mk III's anti-aliasing filter vs. the lack of same in the 645D, and potentially more aggressive processing of the shadow tones in the 1Ds Mk III. From my own work, I think the Canon 35mm full frame sensors clearly have less fully usable, clean dynamic range than the 645D at base ISO.

We'll see how the rumored 35mm uber-sensors perform. But just as my original 5D Mk I continues to outperform much newer but smaller sensor cameras, in several important criteria, I think the 645D and medium format in general will continue to maintain an advantage over the new 35mm super cams.

Of course I'm talking absolutes, and there's no question that gaps get narrower or widen again with each successive wave of technical innovation in a given format. Whether the price-performance of the gap is worth it to some people at a snapshot in time, is a completely different question...

Unknown said...

I shot Pentax 67 MF B&W film (APX 25 and ATP 1.1) for years.

The 645D out resolved the best I could do with ATP 1.1 and APX 25, comparing my own 24 x 36 prints in my hands side by side.

Sold my P67II bodies but kept selected P67 lenses.

Having a blast with this camera and "No Regret".

Greg Brophy said...

I have a Phase One P20 which is only an 18 megapixel camera. I have noticed that the images seem more dimensional, the tonal range is greater and the print out wonderfully at larger size. I have printed up to 30x40 easily. I paid $6000 for a used one and I love it. It also has some downsides. It does poorly in low light. I rarely go above 400 iso. It's very heavy and does not focus as fast as a Nikon. So I guess it depends on what you are going to use it for. I would recommend it for studio and landscape photography in a heart beat, but not street or fast action photography.