noone

I will always have a soft spot for Pentax but they are history and toast. Ricoh saved it as a brand from total oblivion and Ricoh is a big enough company that it can exist as a pimple on the arse as long as it does not lose too much money. I have had a M42 Spotmatic SLR (still have it and a K mount film camera actually) a couple of other film K mount cameras, an IST*D, K100D and Kx DSLRs and a Pentax Q and loved them all....Thing is that my little Sony RX100 iv is probably better than all of them. The K100D and the Q both died prematurely probably because I over stressed the IBIS. The Q was a lot of fun and if I came across a cheap one I would buy it in a heartbeat (but not particularly looking). Do not forget, Pentax tried the mirrorless APSC route with the K-01 in 2012 but that used the K mount so was very niche in a brand that had already become very niche in itself so maybe 1% of a brand that had about 5% of the market at the time and has gone backwards.. I would only buy another DSLR IF it was cheap enough, FF and Canon and just to use my existing Canon mount EF AF lenses. The only Pentax I would consider is that cheap Q if it hit me in the face in the likes of a pawn shop or charity shop. The Pentax 1.7x AF adapter was worth the price of entry to K mount (probably still is for some people).

Great so you DO you think the sensor size has nothing to do with any difference so we do agree! Of course if you do not agree with that, you would be able to prove it with science since you cannot prove it with photos (as any differences in photos taken with systems not identically scaled can be explained by difference in the systems.). Now unless you CAN provide something (ANYTHING) showing how (often tiny) differences in photos could not even remotely be explained by differences in the equipment, I think we have gone several pages too far and I am out Really really really this time).

Not car racing but i think the same would apply as bike racing and years ago even a little with harness racing and greyhound racing. If possible, I would get on the exit side of a corner and facing them as they come out of it. That way they are going slower and it also means you can use a shorter lens, then walk back a bit and do the same with a longer lens like your 600. Closer to the corner will be almost head on. Good luck with it! What do you think of the 600?

A few surprises there. No A7s but the RX100 makes the list? Have both, love both but for video?, no contest, the A7s is my all time favourite camera and the RX100 my all time favourite pocket camera. The little RX100 does have some party tricks though. It does seem to be two lists in one. cameras that are good video camera but cheap and top end hybrid cameras.

Sigh! I do not need to address each point as I disagree with YOUR (no one else its seems) theory that you have shown NO, zero, nil, zilch nix, NOTHING in evidence to support other than saying there are (often tiny) difference so it MUST be because of the sensor size difference. That article explains things pretty well to me and I can not understand how YOU can not understand that ANY difference in a system can explain very tiny differences in photos while at the same time you think those differences are explained by sensor size difference without a shred of evidence why ? The fact that this amounts to many many pages of yes, no, yes, no is reason enough to end it now. This thread should be locked.

I Disagree! Got ANY shred of evidence to support your case?

What system? What focal length would you like? Is that the total diameter or just of the aperture? (a 50mm f2 lens has a diameter of 25mm or about 1 inch but that is not taking into account the rest of the lens). If it IS just the aperture then easy to work out, just divide the focal length by the f stop regardless of system but be sure to use the ACTUAL focal length and not the equivalent one for smaller sensors (a 50mm f2 lens on a Pentax Q is going to be a super telephoto but on a large format camera it is going to be a wide angle). If you mean the total width of the lens, then you would be restricted to progressively smaller systems and ones that are smaller than most system mount diameters.

This is as good a read on this as any. https://www.spiedigitallibrary.org/journals/optical-engineering/volume-57/issue-11/110801/Equivalence-theory-for-cross-format-photographic-image-quality-comparisons/10.1117/1.OE.57.11.110801.full?SSO=1 "Nevertheless, real world IQ differences (including total image noise) will inevitably occur in practice even when equivalent photos are taken. These will arise due to differences in the underlying camera and lens technology, such as: • sensor quantum efficiency; • read noise; • sensor pixel count; • lens aberrations; • JPEG tone curve; and • image processing. In other words, since the total light received by each format is the same when equivalent photos are taken, it is factors such as those above that explain real-world cross-format IQ differences rather than format size. These factors will be discussed further in Sec. 4."

Sorry Tupp but I disagree and that is why there is no point discussing it with me. Again, if anyone wants to ask about this, they are MUCH better off asking in a photography science/technology forum.

I think the biggest thing about digital zoom is if you start with a good lens, the results zoomed can still be better than lesser lenses. These are in low light indoors so ISO 25600 even with flash used with a 300 2.8 at 2.8 and with 2x clearzoom.

I love Sony clearzoom. The thing is it is VARIABLE so even a very fast prime becomes a 2x zoom with little loss of image quality. Most recent (if not all) Sony digital cameras have both clear image zoom and digital zoom (clearzoom is to 2x, digital zoom is to 4x). I do not know what (or if) there is a difference between clearzoom and digital zoom at and below 2x. Sony cameras give the option of optical only, clear image zoom or digital zoom. I usually have my A7s set to be able to use clear image but my RX100iv most of the time is set to optical only. Towards 2x clearzoom CAN have that digital zoom look sometimes but it also comes in handy for using smaller format lenses that do not cover FF. I have the A7s set so I can use it on the fly and including for video. Looking for a better remote control that will let me use it (my current cheap remote is not great using it). I did not mind ETC on the GX7 but it was not something I used often. I think the A7siii does not allow clearzoom in 4k video?? Did I see that?

Just looked at the EXIF for my Sigma 150 2.8 macro in Canon EF mount adapted to my E mount camera and it reports as being an 18-280 3.5-6.3 lens (everything else that matters is correct). I THINK (no evidence either way) it is correcting vignetting slightly. Mine is an older first generation A7s so I do not think it corrects as many things as newer cameras but again, that is yet to be confirmed.

1) Equivalence theory HAS been tested and is accepted by the majority of photographers and scientists. Most accept it even though no one has done an EXACT match (IE the photos LOOK very similar but someone will always point out a tiny difference) to the satisfaction of SOME but the deniers have never shown evidence that it is wrong either. The problem in getting an EXACT match is you would have to scale the equipment for an EXACT match and that would be near impossible. To the point the EASIEST way might be to build from scratch very simple low element number formulas that test this (but may not be great images). There ARE science and technology forums on photography on various sites, so much better to ask in those rather than old format warriors on a video forum. 2) Nah, it would work for me but there will still be tiny system differences (lens formula ETC) that way which again to me would easily explain tiny difference in the photos but not others. Remember, focal reducers do not change cameras, they change lenses so everything else still applies (some lenses have been MADE by tacking a focal reducer group onto an otherwise different lens). Third party lenses CAN apply corrections but it depends. Sony for example opens its mount to other manufacturers and M43 is an open mount too (they have to sign confidentiality agreements. Canon and Nikon do not and the likes of Sigma have to reverse design. Even my Canon EF lenses on my A7s report the EXIF but the lenses get recorded as different Sony lenses so it MIGHT be correcting things but doing it as if it is a different lens though it still might be doing it right. Then again, most of my Canon lenses are older that need less correction (or none). In camera correction is not necessarily a bad thing as it means they can make lenses better in other areas (or cheaper or both). My old Canon EF 20-35 2.8 L is probably better corrected than its great great great grandson (the 16-35 2.8 L iii) but the newer lens is a MUCH better lens. I would love to do a comparison to see how they both go adapted to my Sony but the cost to experiment is far to high. Olympus M43 lenses are some of the MOST corrected in camera and yet they are still extremely nice (yet not so long ago the 43 DSLR lenses were made large enough to cover APSC (at least in some cases) and would hardly have needed any correction. Sony E probably corrects for vignetting which probably explains why DXO often shows FF E mount lenses with the F stop and T stop being the same.

Using the .13 crop factor would actually mean it IS very doable to "match" (enough to satisfy me anyway) with a 600mm f9 (or even f8) 8x10 lens to M43. Using .13 instead of .15 as the crop factor, you would need about a 39mm f1.2 lens for the f9 or an f1 lens for the f8. (again though, we do not know what it actually was). A 40mm 1.2 would give a close enough photo. but you could even use an existing Kipon 40mm f0.85 (a lens for both M43 and APSC formats) and keep the change! Just found that interesting and I would love to see someone do a direct comparison (between an 8x10 camera anyone got a digital back that size with a 600mm f8 lens who also has M43 with a Kipon 40 f0.85? Great! I look forward to the tests).

Interesting. It seems there is disagreement on the crop factor of 8x10 format. Some sites say .15x (600mm would be 90mm equivalent) some say .13x (600mm would be 78mm equivalent). I guess you would never get an exact match due to the different aspect ratios. crop factor calculator sites give 78mm though so I am happy to go with 78mm equivalent if it matters as that does not change anything (differences being down to optics, not sensor size)..

I wrote a very long post replying (and mostly disagreeing) to all your individual points but have just deleted it as there is no point continuing. All I will say is this.. The crop factor to FF for an 8x10 camera is .15 which means it is a 90mm equivalent lens. We do not know what the aperture was for that photo, I do not know if it would be possible to get the same photo (if it was an F9 or f12 lens then YES, it would be POSSIBLE but you would first have to have a lens of the exact same formula and match the crop exactly which no one is going to do ...again, that is WHY I prefer FF, I can get lenses I can not match with M43. It seems to me 1) We AGREE that there are lenses available for some systems that are not available for others. 2) You believe there is a difference between formats to the point if anyone ever does do an EXACT scaled match between formats there would still be a difference in the photos. (I do not). Happy to reply further if you ever post a test or a link to a test that DOES match system EQUIPMENT exactly.

The thread title? Every lens is different and sometimes a slower lens may well be better at certain apertures than a faster one more usually it isn't (at least mine have not been).

Kye, sometimes f2 and faster are needed for valid reasons. The OP stated they needed that so that was ALSO a criteria. I agree about most (though not all) lenses are better stopped down. The few exceptions are usually very expensive. Often there is a bit of a myth about slower lenses being better than the faster version of same. I would always take a good fast lens over a good slow one unless the size became unmanageable. I do sometimes wish my very old A mount AF Sigma 180 5.6 macro lens was in Canon mount or Sony E as I would love to use it from time to time due to its small size (though my Sigma 150 2.8 macro is light years better).

I have had a LOT of 50s and near 50s. Very few are what I would consider sharp wide open though it is relative and none of the cheaper ones I have had would be. MAYBE used on your camera they would be ok as they are not using the worst part of the lenses. The best by far for me is the FE Sony Zeiss 55 1.8 which IS sharp wide open but that is no help to you. One cheapy that i had and really liked was the Nikon 50 1.8 AF (non D made in Japan version). Maybe any of the Nikon 50 1.8s? would be a reasonable combination of cheap/sharp enough? IF you could find one in your price range, the FD 50 1.2 L (not the non L) is sharp in the area in focus at 1.2 and it is better stopped down a little so still fast. The same with the Pentax 50 1.2 I had though no asperic elements in the Pentax there is in the FD L (those two might be too dear though.

Too late to edit 1.2 FF is more like f0.60 M43.

If you do NOT get things to match exactly there will ALWAYS be a small difference that will just leave SOME to say that because there is a difference the theory does not match the practice and THAT is what makes even trying a "fools errand" All the tests to date look close enough for me, if they do not for you, that is your problem and you should be doing the tests to match YOUR theory. You think the tests get close enough but then when you see a(often very small) difference you attribute that to a difference between formats instead of between the optics. There is no reason you would get a difference in vignetting if you used identical formula lenses to match the crop (IE scaled). As to your 600mm 8x10 above, That is a very different argument and actually plays into the original question and is again the reason WHY FF is necessary to ME. I simply can NOT match my ancient 300 2.8 with M43 (other than the $35000 plus Arri 150 1.3) or my ancient 24 1.4 (because there are no 12mm m43 f0.7 lenses) or my ancient 85 1.2 (again, no 42.5mm f0.65 lenses which is approaching the limit in air). No high quality tilt shift lenses either like my favourite 17 f4. If I could do what i can with m43 (or Pentax Q) what i can with FF, I would only be using that. A 8x10 camera with a 600mm lens will probably be something like a 600 f9 Nikon. A 600mm 8x10 f9 lens would be equivalent to about a 90mm 1.4 FF (so about a 45mm f0.7 M43). If you COULD get a lens to match it (it IS possible even if there are none) it would yield a very similar photo even without being the exact same lens design. If the lens was 600mm f8, then that would be almost impossible to match with m43 as that would be about a 90mm f 1.2 FF so you would need an aprox 45 f0.65 to even give a similar if not exact photo. You have yet to show that there is ANY difference BECAUSE of the differences in sensor size and so far all difference have been because of the optics and not getting an exact match. After all if the Moon astronauts had been just 2% off course, where would they be now?

Of course he did. But if you use the same optics in different formats you get the same result...it is not the format that makes the difference it is the lenses. To get an exact match to satisfy everyone, You would need to firstly pick your cameras of different formats and get the EXACT crop factor. Next you need a lens for one format. You would need to know the actual focal length (not just the marked focal length), You would need the diameter and could then work out the exact f stop. Using the crop factor to get an exact match, you would then need to do the same for the second format. You will also probably need to have the exact same lens formula though to get the same T stop (and take away any possibility of being a difference for other reasons). Yeah, it probably IS possible (maybe even easy for some). I could not do it in a lifetime though and again, beyond being a academic exercise, what is the point? It would HAVE to be done this way because otherwise some will point out (often tiny) differences but those differences . So, unless you (or someone else) does THAT, I will always accept that the theory matches the practice and to date, all tests have satisfied me they do. Are there ANY tests that have been done matching equipment EXACTLY?

When I use my two different FF 24mm lenses both made by Canon but one EF and the other FD (both quite old though), I can often see almost as big a difference as between my FD 24 1.4 L and my RX100 iv at 24mm equivalent (actually the EF 20-35 2.8 lens is a closer match usually maybe because it fully passes exif to the camera while the FD adapter is dumb). As with all of these, the small difference are down to many reasons mostly including the lens design but also the settings are usually not exact (IE one 24mm lens might be 24.5 while another might be 23.8mm). The numbers to get an exact match between an 8,8mm lens on the RX100 and the 24mm on FF I use are aprox and the crop factors used are aprox. This is why it would be almost impossible to get an exact match and I doubt even Lens Rentals and their optical bench could get one. Since I very much doubt you will EVER see an exact match, some people will never accept the theory matches the practice and hence discussion like this are pointless (the why /why not use FF or any other format can be a very valid discussion but not the equivalence is real ones). Read the other thread linked to earlier and what Dr Caldwell said (he designed the Metabones SpeedBooster as well as one of the highest performance lenses ever). Back to (trying to) be a spectator.

Buy me a Arri master prime 150 1.3 and an adapter to use it on M43 and I will happily compare it to my ancient lowly Tamron 300 2.8 FF. As for the rest, in your reply to me above, I disagree

10 bit is not something that was available on most cameras until quite recently. The Canon R5 has it but only in log so for people likely to be more serious about video. The A7C is not aimed at more serious video users. The recent Sony cameras that ARE and I would imagine any future Sony cameras that are aimed at serious video users will all have 10 bit (as will everyone else).