[clackers]

In a studio with mains powered light setups, f5.6 and f8 and even f11 are desired, because you want the image to be super sharp.

[LensBeginner]

Total light? That's meaningless. Take an 8x10 view camera. Place an 8x10 sheet film negative on it - expose. Now take a 4x5 piece and place into the same camera. Expose. Now a 2.25"x2.25" etc. All come out with the same exposure. Sensor size does not change the light per unit area. where it gets tricky is that the size of the pixels may not be consistent and here it is the same as changing the film between shots. Some variation creeps in. This is not due to simply size but practical limitations of sensors that are large vs. small and cost. In truth this mainly manifests in the area of noise - with smaller pixels being less noise tolerant. Look at the performance of the 12mp FF Sony vs. a 30MP Canon in low light to see what I am talking about. However even in this case - the baseline exposure for a given lens in the same lighting with the same ISO settings should remain similar. The extremes come in when you push the ISO capabilities for low light.

It's not meaningless.
Total light might have nothing to do with exposure, but it certainly has with the final result.
Practically speaking, just select the next ISO (about 1 stop between APS-C and FF, unsure about FF-MF) and you'll have the same noise as the smaller sensor, while compensating for the smaller aperture.

[romay]

Total light? That's meaningless.

I think that's a dangerous, thing to say. Of course, total light doesn't factor in when it comes to exposure. But this is photography 101, whoever doesn't know that already just isn't ready for medium format, period.

However, in a controlled (studio) environment, where you are not constrained by exposure times and/or aperture or where you can crank up your flashguns all the way you like, total light is the *only* thing that matters. Total light is the signal you're getting from your sensor. The more energy it contains, the better the S/N ratio. For a given print size, the amount of energy your sensor absorbed dictates your S/N ratio. Not even the pixel sizes play a role here, a 10x15 print will have the same noise no matter how many megapixels you divided your sensor into.

In other, more constrained environments, like sports or wildlife, the situation is different. In that cases total light doesn't matter because a certain scene only gives you a fixed amount of photons to work with. If you record more than that, you blur your scene in the time and/or the spatial domain. In this case, it doesn't matter much how big the sensor is that captures that predefined set of photons.

[Don Fischer]

I am not a studio photographer but did fool with it a bit. Got a set of light's and set up in my living room. I have an el cheapo flash meter and used a white sheet as a background. With the sheet back ground, it seemed that I could do a small an aperture opening as I wanted. I don't recall the shutter speed I used but the flash meter gave me an aperture of f11. Shot at that and the photo's came out really really sharp. In a studio I suspect it's fairly easy with an artificial back ground to use as ssmall an opening as you can. If you want boka, can't that be accomplished by choice of back ground ans a small aperture opening?

[stevebrot]

It's not meaningless.

Perhaps not completely meaningless, but close to it. I won't go into the technical details, but quite a bit of the equivalence stuff is dependent upon a series of sketchy assumptions*. The fact that you are not sure about determining FF-MF equivalence is a good indication. Another good indication would be the lack of historic obsession about such. I have been doing film photography for a number of decades and nobody (I do believe that means zero) is particularly concerned with calculating the equivalence (in stops or any other units <rolls eyes>) between 645 system lenses coupled with available cameras and films and 6x7, 35mm, 4x5, or 8x10 with same. Why? Because it is not very meaningful.

What is meaningful is whether available optics are fast enough for adequate DOF/focus control while addressing practical considerations such as appropriate shutter speed, focus system, available lighting options, available capture media, size, and weight. Thankfully, these details have been worked out through many years of field experience. What is on the shelf to buy generally represents what works.


Steve

* Occam's Razor: "That proposition requiring the least number of assumptions has the highest probability of being correct."

[redrockcoulee]

You could use a 2.8 prime if you wanted to.

[bull drinkwater]

I have the two zooms you mentioned and out oif doors 5.6, 6.3, or 8.0 is no problem. in the studio, with you in control of the lighting, there should be no problem.

[gavincato]

This is quite likely a really dumb question, but as a medium format total newb, I have to ask it.

I'm planning the Big Move from K-3 to 645Z. The body is the easy part. Now I'm examining my lens options and this is where it all goes sideways.

My two most used lenses in studio are DA* 16-50/2.8 and DA* 50-135/2.8. And they have exact equivalents in the Full Frame world: 24-70 and 70-200. So if I was planning the move to FF, I'd be ready to order.

But looking over the lens list and in speaking with studio shooters, the two more or less equivalents in the 645 lineup are the 45-85mm and the 80-160mm. Yeah, not quite the same thing but whatever.

However both of these are f:4.5 glass. WTF? Losing a stop and a third of light? How and why is this acceptable to studio shooters? Is there something that happens optically in the 645 system that makes this no big deal? Does the large bright viewfinder somehow make this all better?

<whine> What about my beautiful f:2.8? </whine>


Thanks in advance!

I'm actually struggling to see the problem. In a studio you often use f8-f11 or thereabouts. It's outside with natural backgrounds that you might want 2.8

However that aside, if you are concerned about focus, live view is your friend.

[Digitalis]

Fast lenses (e.g. f/3.5 and faster) with large image circles tend to be a little on the huge size and I do mean huge.

True, If the Canon 85mm f/1.2L was made for 4X5 and was proportional in size, the lens would be the size of a watermelon. Medium format has multiple f/2.8 primes which are still quite compact, Consider yourself lucky lenses with apertures of f/2.8 and faster are rare for 4X5 and are equally rare on 8X10 format*.

* the rather uncommon Aero Ektar 307mm f/2.5 springs to mind - an older lens designed to cover 8X10, although it has severely restricted movement capabilities compared to contemporary lenses. Most 8X10 lenses made these days are around f/4 at the fastest and most have generous movement capabilities.

[672]

To the original poster. You might want to rent and test first. Those two zooms , designed in the film days and never updated, do NOT look very great at f4.5 on a 645Z. They look acceptable at f6.3. Whereas any modern Canikon with the latest version of zoom will look good right away at f3.2.
Also, many including myself do not like the tight end of the 80-160mm at all . So zoom range is about 45-130.....using both zooms. At f6.3.

[LensBeginner]

Perhaps not completely meaningless, but close to it. I won't go into the technical details, but quite a bit of the equivalence stuff is dependent upon a series of sketchy assumptions*. The fact that you are not sure about determining FF-MF equivalence is a good indication. Another good indication would be the lack of historic obsession about such. I have been doing film photography for a number of decades and nobody (I do believe that means zero) is particularly concerned with calculating the equivalence (in stops or any other units <rolls eyes>) between 645 system lenses coupled with available cameras and films and 6x7, 35mm, 4x5, or 8x10 with same. Why? Because it is not very meaningful.

What is meaningful is whether available optics are fast enough for adequate DOF/focus control while addressing practical considerations such as appropriate shutter speed, focus system, available lighting options, available capture media, size, and weight. Thankfully, these details have been worked out through many years of field experience. What is on the shelf to buy generally represents what works.


Steve

* Occam's Razor: "That proposition requiring the least number of assumptions has the highest probability of being correct."

"I'm not sure" only because I don't have time nor will to do the math... but it's only a matter of area vs area. I.e. I'm not sure of the exact number, not of the fact that there's a difference - assuming same underliying tech of course, CCD vs CCD, CMOS vs CMOS etc.
And no I still don't believe it's irrelevant; and while being a fan of Occam's Razor myself, I don't think it applies here.
However the OP point still stands, maybe you don't lose a stop and a half because you make up part of it with the larger sensor, but at least half a stop, yes.

Bottom line for me and my shooting: MF is too expensive for generalistic use, for that we have FF, APS-C, mu43 etc. it's only a matter of price, portability, "quality" etc.
I couldn't stand not being able to choose from so many different lenses, each with its own characteristics, even in the same focal length range. With MF it's those few lenses and they are way too expensive to afford duplicates...

[rfkiii]

Perhaps not completely meaningless, but close to it. I won't go into the technical details, but quite a bit of the equivalence stuff is dependent upon a series of sketchy assumptions*. The fact that you are not sure about determining FF-MF equivalence is a good indication. Another good indication would be the lack of historic obsession about such. I have been doing film photography for a number of decades and nobody (I do believe that means zero) is particularly concerned with calculating the equivalence (in stops or any other units <rolls eyes>) between 645 system lenses coupled with available cameras and films and 6x7, 35mm, 4x5, or 8x10 with same. Why? Because it is not very meaningful.

Equivalence has long been a big deal to users of the 35mm format. Folks want to know what the equivalent DoF and FL are for lenses that can be mounted on either system in order to leverage reach, width or DoF before they make expensive purchases. Now that Pentax has a cropped 645 sensor, seems like a good idea to at least consider it since many of the lenses available were made for FF 645. In fact, I was wondering what the equivalent FL would be for the FA 400mm when mounted on a 645z. Seems like a good thing to know/calculate when considering adapting legacy 6x7 lenses to the 645z too.


As for cross-platform equivalence, blame Pentax somewhat for nurturing that thought process as they note 35mm equivalent FL numbers on their website as well as in the EXIF of an image when viewed in Utility 5. 35mm equivalents are provided in the lens review section of this website.


The preceding is more important during the purchase phase. Once the lens is mounted, one will have to use the FOV and DoF provided.

[stevebrot]

Equivalence has long been a big deal to users of the 35mm format.

Truly...You mean people like me? I have been shooting 35mm for about 45 years and there was no angst in regards to equivalence when I broadened to APS-C. Similarly, there was no angst when I broadened to 6x7 and 4x5 a few years ago. In fact, the first I ever heard of equivalence was on this Web site and then only about two years ago in the FF speculation threads. I have several books on photography dating back to the early 1970s and none discusses equivalence, though most consider multiple formats. I also belong to several online film photography forums where the old guys hang out and they, along with the film people on this site, also never discuss equivalence. Go figure...

BTW...when I hear the term in relation to photography, my first thought goes to articles like this:

http://www.jnevins.com/whitereading.htm


Steve

(...perhaps it is a measurebation sort of thing...I dunno...)

[Kolor-Pikker]

When talking about equivalence, keep things like pixel density in mind more than mere conversion of focal lengths.
For instance, 150mm on the 645Z is like 130mm on FF35, but the pixel density is around 45% higher than a Canon 5D2/3. If those are the cameras you're used to using, you will find that you'll still get more pixels on the subject despite the wider FoV.
So in situations like wildlife photography, where your reach is a function of pixel density amplified by focal length, 150mm on the 645Z is equivalent to 190mm on a 5D3.

[Digitalis]

also belong to several online film photography forums where the old guys hang out and they, along with the film people on this site, also never discuss equivalence.

On the Leica forums I frequent, any mention of equivalence will be followed by complete silence. Leicaphiles do not tolerate Noobs....especially ones that only have a Hexar RF.